Medicine
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Diseases, disorders and conditions
Acne
Acne is a common skin condition that affects most people, usually when they are teenagers or young adults. It is commonly brought on by the changes in hormone levels during puberty. Acne occurs when hair follicles are clogged with dead skin cells and oil from the skin. This results in spots, mostly on the face, but they can also appear on the back and chest. Spots that occur with acne include blackheads (small bumps that are black because of the colour of the inner lining of the hair follicle), papules (small red bumps that may feel tender) and pustules (similar to papules, but with a white tip in the centre, caused by a build-up of pus). Acne cannot be cured, but it often goes away when a person reaches their mid-twenties. It can be controlled by treating spots with creams, lotions and gels—although these may take some time to work.
Allergies
An allergic reaction happens when a person’s immune system, which protects the body from disease, reacts to a usually harmless substance. Common allergens—causes of allergic reactions—include plant pollen, which causes hay fever, dust mites (which live among household dust and dirt), animal skin and hair, foods such as peanuts or shellfish, insect stings and particular medications. Symptoms of an allergic reaction include a runny nose, red eyes, itchiness, eczema, hives (a red, bumpy skin rash) and asthma attacks. Severe allergies can cause a life-threatening reaction called anaphylaxis, which may lead to swelling and breathing difficulties.
Anaphylaxis is treated with injections of the medicine adrenaline (also called epinephrine). Immunotherapy is a long-term treatment that aims to reduce the body’s reaction to allergens by giving small, but increasing, doses of the allergen.
Alzheimer’s disease
Alzheimer’s disease is a form of dementia (see below), which is a group of diseases of the brain that cause loss of the ability to think clearly. Early symptoms of Alzheimer’s include trouble with memory and language. It is a degenerative disease, which means that it gets worse as time goes on. Eventually, the disease takes away the brain’s ability to control bodily functions, causing death. Most people diagnosed with Alzheimer’s are over 65 years old. There is currently no cure for the disease, but there are treatments to help with some of its symptoms. The causes of the disease have not been fully discovered, but doctors and scientists are doing lots of research to try and find out more about it.
Anaemia
Anaemia is a very common blood disorder, affecting around 2 billion people. Anaemia is when there are not enough red blood cells in a person’s blood, or not enough haemoglobin in their red blood cells. Haemoglobin is a protein that does the vital job of carrying oxygen around the body. Symptoms of mild anaemia include tiredness and shortness of breath. Severe anaemia may cause heart problems.
The most common cause of anaemia is lack of iron, which prevents the body making enough haemoglobin. This may be caused by a person losing blood (and the iron it contains) because of medical conditions such as peptic ulcers or bowel cancer. It may sometimes be caused by not eating enough iron in the diet. This is especially true in pregnancy where a woman needs more iron, when a change in diet or iron supplements (tablets) may help. There are many other less common causes of anaemia including lack of certain vitamins, genetic disorders, and leukaemia (cancer of the blood).
Appendicitis
Appendicitis is a painful swelling of the appendix, a small, thin pouch connected to the large intestine or colon. It is probably caused by a blockage to the entrance of the appendix, most commonly due to a hard piece of faeces. A build-up of bacteria inside the appendix leads to infection, inflammation and swelling. The symptoms of appendicitis usually start with pain in themiddle of the abdomen, which then moves to lower right side (where the appendix usually lies). This may become severe. If the swelling is left untreated, the appendix may burst, leading to serious complications.
In most cases of appendicitis, the appendix must therefore be removed as soon as possible. This is a common operation, performed as keyhole surgery (laparoscopy). Most people make a full recovery in a couple of weeks.
Arthritis
Arthritis is a disease that causes painful swelling and stiffness of the joints. It can lead to loss of movement in certain joints or not being able to walk. In many developed countries, arthritis is the most common cause of disability. There are more than 100 types of arthritis, including osteoarthritis, usually caused by ageing or by damage to a particular joint, and rheumatoid arthritis, a disease of the immune system that causes swelling of joints and other tissues.
There is no cure for osteoarthritis or rheumatoid arthritis, but medications can reduce pain and swelling, while careful exercise can help with movement. In severe cases, damaged joints—particularly knees and hips—can be replaced with an artificial joint.
Asthma
Asthma is a common disease that causes inflammation (swelling) of the body’s airways. Symptoms include shortness of breath, wheezing, coughing and a feeling of tightness in the chest. Asthma attacks may be triggered by lots of things including respiratory infections (colds, flu), allergens (house mites, pollen), exercise or even going out into cold air. Symptoms are treated and prevented by inhaling (breathing in) medications to reduce the swelling in the airways. Severe attacks must be treated in hospital with more powerful medications.
The causes of asthma are not fully understood but may be a mix of genetic (passed down from parent to child) and environmental factors, such as early exposure to infections, cigarette smoke or air pollution. Around half of children diagnosed with asthma will no longer be asthmatic 10 years later.
Autism
Autism is a life-long developmental condition. It affects how a person communicates and experiences the world around them. Autism affects people in different ways. People with autism can find it hard to understand other people's feelings and have difficulty taking part in conversations. They may find things like loud sounds and bright lights distressing and confusing. They may show restricted and repetitive behaviour. Some autistic people have learning disabilities, and need lots of support to help them lead fulfilling lives. Others need little or no special support.
Autism may be caused by a mix of genetic and other factors, including certain infections and toxins (poisons) during pregnancy. The suggestion that vaccination against certain diseases causes autism is false. It is known that autism affects the way the brain processes information, but exactly how this occurs is not well understood. Autism and less severe forms of the condition, including Asperger syndrome (also known as Asperger's), have been combined into what is known as autism spectrum disorder (ASD).
Although there is no known "cure", children with autism can be helped to look after themselves and gain social, and communication skills. Speech and language therapy, occupational therapy and educational support are among the ways that help can be given. Today, many experts believe autism should be accepted as a difference and not treated as a disorder.
Bipolar disorder
Bipolar disorder, previously known as manic depression, is a condition that affects moods. People with bipolar disorder have episodes of both depression (feeling very low and sluggish, sometimes leading to thoughts of suicide) and mania (feeling very high and energetic, sometimes leading to psychosis—seeing or hearing things that are not there or are not true). Each episode can last for several weeks; some may not often experience a "normal" mood at all. Bipolar disorder can be treated with medication designed to stabilize moods, and psychotherapy, helping the sufferer dealing with depression and improving relationships with others. The cause of bipolar disorder is unknown, but a mix of genetic factors and life experiences are believed to play a role. Extreme stress can trigger an episode.
A fairly common condition affecting around 1% of the global population, bipolar disorder most often develops in the teenage or young adult years. Men and women are equally likely to develop it. The pattern of mood swings in bipolar disorder varies widely between people. Some have only a few bipolar episodes in their lifetime, while others may have many episodes.
Brain tumour
A tumour, or “lump”, is made when body tissue grows in an abnormal way. Tumours may grow anywhere in the body, including the brain. Tumours are often described as either “malignant” or “benign”. Malignant tumours are cancerous and will spread to surrounding tissue if they are not treated. Benign tumours are not cancerous and will not spread. Though usually easier to treat, even a benign brain tumour may cause headaches, vomiting and problems with sight and memory. Treatment of brain tumours may involve surgery to remove the tumour, or radiation therapy to kill the abnormal cells.
Bronchitis
Bronchitis is an inflammation (swelling) of the lining of the bronchial tubes, the larger airways in the lungs. Bronchitis can be acute (lasting just a few weeks) or chronic (a long term condition). The main symptom of acute bronchitis is coughing, which may bring up mucus. The condition is often caused by a virus, such as a cold or flu, which infects the airways. Most infections get better without treatment.
Chronic bronchitis is a long-term disease of the lungs, causing coughing, mucus and shortness of breath. It is often brought on by smoking. Treatments include medication, oxygen therapy (breathing oxygen through a mask or nasal tubes) and special exercise programmes.
Cancer
A human body is made up of trillions of cells. Sometimes, abnormal cells multiply in an uncontrolled way, often forming a tumour, or “lump”. Cancer is the name given to a large number of diseases in which this takes place. A tumour can stop the body working properly, by pressing on organs or upsetting its chemical balance. The cancerous cells can invade healthy body tissues nearby and may enter the bloodstream, spreading the disease to other organs.
There are more than 200 types of cancer. They are often named after the organ or cell in which they start: for example, lung cancer.
Cancer can be life-threatening, but if it is spotted quickly, it can often be cured. Common treatments for cancer include surgery to remove cancerous cells, chemotherapy, radiation therapy, hormonal therapy and targeted therapy—all methods of controlling or killing cancerous cells. Some cancers can be prevented by eating a healthy diet, exercising, wearing sunblock during the summer, not smoking, and being vaccinated against particular infectious diseases.
Cataracts
Cataracts are the world’s biggest cause of blindness. The clouding of the lens is thought to be due to changes in the proteins inside it. The lens focuses light on to the retina. A cataract is when the protein in the lens starts to clump together, clouding an area of the lens. Cataracts are more common in older people but the chance of getting them is also higher after eye injuries, after over-exposure to ultraviolet light and with certain diseases such as diabetes. Cataracts are treated with surgery, in which the cloudy lens is removed and replaced with a clear plastic one.
Cerebral palsy
Cerebral palsy (CP) is the name for a number of movement disorders that appear in early childhood. Symptoms include poor co-ordination, stiff or weak muscles and tremors. Babies with cerebral palsy may not sit, crawl or walk as early as other children of their age. Cerebral palsy is caused by underdevelopment or damage to those parts of the brain that control movement and balance. The problems occur during pregnancy, during birth or shortly afterwards. Often, the cause is not known. Although there is no cure for CP, treatments (including physiotherapy and occupational therapy), medication, surgery and technology can help many children to achieve near normal adult lives.
Chickenpox
Chickenpox is a highly contagious (easily spread) disease, common among children, caused by a virus. Symptoms include itchy red spots that turn into fluid-filled blisters and eventually scabs. A person with chickenpox is infectious from two days before the rash appears until all the spots have formed scabs. The virus (called Varicella zoster) is airborne, which means it is spread through coughing and sneezing. It remains harmlessly in the body after symptoms have disappeared, but can sometimes become active again in later life, causing shingles, a painful rash.
Although chickenpox is not usually serious in children, it can cause complications in pregnant women who are not immune, and in people with a weakened immune system, the body’s defence against disease.
Cholera
Cholera is a disease that affects the small intestine. It is caused by infection with the bacterium Vibrio cholerae. Symptoms include watery diarrhoea and vomiting, which can lead to dehydration (loss of body water) and loss of vital salts. If not treated, cholera can cause death. The infection is spread by drinking water or eating food that has been contaminated with the faeces (waste) of an infected person.
The disease is no longer common in developed countries, but kills 100,000 people a year in regions with poor sanitation. The key treatment is to rehydrate the infected person, by giving them water mixed with sugar and salt.
Cirrhosis
Cirrhosis is the scarring of the liver due to long-term damage. Healthy liver tissue is replaced by scar tissue, preventing the liver from working properly. The disease usually develops slowly over months or years. As it worsens, the person with cirrhosis may become tired, develop yellow skin and have fluid build-up in the legs and abdomen. Eventually the liver may fail altogether which, unless the person receives a liver transplant, will lead to death. Cirrhosis is most commonly caused by alcohol, hepatitis B and C or by non-alcoholic fatty liver disease resulting from being overweight, diabetes and high blood pressure. The damage to the liver cannot be reversed, but treatment can slow the progression of the disease and help to prevent complications developing.
Cold sores
Cold sores are small blisters that develop on or around the lips. They are caused by the herpes simplex virus (HSV-1) and usually clear up without treatment within a week or 10 days. Antiviral creams can help ease symptoms and speed up the healing time. Cold sores often start with an itching feeling around the mouth. Small, fluid-filled sores then appear. The herpes simplex virus is highly contagious and can be easily passed from person to person by direct contact. After someone has contracted the virus, it remains inactive (dormant), to be re-activated weeks or months later. This may be triggered by a range of things, including sunlight, fatigue or, in girls and women, their menstrual period.
Common cold
A cold is a mild disease of the upper respiratory tract, which includes the nose, throat and sinuses (air-filled spaces around the nose and eyes). Colds are caused by more than 200 viruses, the most common being rhinoviruses and coronaviruses. The viruses are spread by an infected person coughing or sneezing into the air, or accidentally putting their mucus on objects or other people’s hands.
The symptoms of a cold are caused by the body’s immune system fighting the virus. They include: a runny nose, sore throat, cough, tiredness and low fever. No cure exists, but sufferers get better within ten days—although some symptoms may persist for three weeks. Occasionally, colds lead to bronchitis, pneumonia or bacterial infections in the ear, throat or sinuses.
Covid-19
Covid-19 is an infectious disease caused by a new member of the family of coronaviruses, called Severe Acute Respiratory Syndrome Coronavirus 2 (Sars-CoV-2). The disease was first identified in December 2019 in Wuhan, China, and has since spread globally, resulting in the 2020–21 pandemic. Common symptoms include fever, dry cough and shortness of breath. Other symptoms may include fatigue, loss of smell, muscle ache and abdominal pain. While the majority of cases result in mild symptoms, some lead to pneumonia, organ failure and death.
Because the strain of coronavirus that causes Covid-19 was new to humans, when the outbreak began, no one had prior immunity to it. Our immune systems had no memory of antigens from such a pathogen and so could not produce antibodies to combat it.
At the time of outbreak, no vaccine was available either, meaning the virus was able to spread across the world unchecked. Since then, a number of vaccines were successfully developed and approved in record time. As of April 2022, 11.3 billion Covid-19 vaccine doses had been administered worldwide.
The virus is spread from one person infected with the virus to another person mainly through close contact and via droplets produced when someone breathes, talks or sings, coughs or sneezes. It is also possible (but rarer) to be infected after touching a contaminated surface and then one's face. Recommended measures to prevent infection include social distancing—staying at least 2 metres (6 feet) apart—and frequent hand washing. People infected remain contagious for up to 20 days, and can spread the virus even if they do not develop any symptoms (are asymptomatic) themselves.
Cystic fibrosis
Cystic fibrosis (CF) is a genetic condition (passed down from parent to child) in which the lungs and digestive system become clogged with thick, sticky mucus. This leads to a number of problems from a young age, including breathing difficulties, chest infections, diarrhoea and diabetes. Although there is no cure, there are a number of treatments, including antibiotics and other medications, that ease the symptoms.
To be born with cystic fibrosis, a child must inherit two copies of the faulty gene: one from each of its parents. Because they carry only one faulty gene and one that works normally, neither parent will have the condition themselves.
Deficiency diseases
Deficiency diseases are caused by a lack of certain nutrients in a person’s diet, or by difficulty in digesting or using particular nutrients. Deficiency diseases are often a result of malnutrition, where people cannot get enough of the right things to eat to stay healthy. For this reason, deficiency diseases are commoner in poorer countries. However, iron deficiency, which causes anaemia, and vitamin D deficiency, which causes poor bone growth, are found throughout the world.
Iron is found in red meat, leafy greens and egg yolks. The main source of vitamin D is sunlight but it can also be found in oily fish (salmon, sardines) and eggs. Other deficiency diseases include scurvy (a lack of vitamin C), beriberi (vitamin B1) and pellagra (vitamin B3). In most cases, these diseases are cured by improved diet.
Dementia
Dementia is a group of diseases of the brain that cause loss of the ability to think clearly. Alzheimer’s disease and vascular dementia (which is often caused by strokes) are the most common forms. Another form of dementia is Lewy body dementia which is linked with Parkinson's disease. Dementia is uncommon in people aged under 65, but common in elderly people: nearly a third of people aged over 85 have dementia. Early symptoms include problems with memory, speech and emotions. Most forms of dementia get worse over time and cannot be cured. Symptoms may be eased by medication, exercise and support.
Dengue fever
Dengue fever is a tropical disease, common in Asia, Africa and Central and South America. It is caused by four different strains of a virus spread by a species of female mosquitoes. Symptoms include a widespread skin rash, high fever, headache, vomiting, loss of appetite, muscle and joint pains. Most people with dengue fever recover after three or four days, but in a few cases, the disease develops into more severe forms, resulting in severe abdominal pain, bleeding and dangerously low blood pressure levels. A vaccine for dengue fever exists but is not widely available and seems to be useful only for those people who have already been infected with one of the dengue virus strains. Avoiding being bitten remains the best way to prevent contracting the disease. Treatment of dengue includes pain relief and taking fluids. People with severe dengue fever may need hospital treatment. Untreated, severe dengue fever may lead to death.
Diabetes
Diabetes is a condition that arises when a person’s blood contains too much of a sugar called glucose. The amount of glucose is controlled by a hormone called insulin, which is made by the pancreas, a gland behind the stomach. As food is digested, starches and sugars are broken down into glucose, which enters the bloodstream. Insulin helps the body's cells absorb glucose, which they use to make energy. People with diabetes do not have enough insulin to perform this task.
Type 1 diabetes is caused by the body not making enough insulin. It cannot be cured but can be managed with injections of insulin. Type 2 diabetes is much more common and is linked with obesity, a lack of exercise and older age. In this type of diabetes the body may not make enough insulin or the body's cells stop responding properly to insulin. Type 2 is managed by better diet and exercise, along with medication to control glucose levels.
Diarrhoea
The medical definition of diarrhoea is having three or more loose or watery bowel movements in a day. If diarrhoea lasts for a few days, it can cause dehydration (loss of body water). This may be treated by drinking more water and other liquids than usual, or the person may need to drink a special rehydration solution (water containing sugar and salts). Diarrhoea is often the result of an infection of the intestines, caused by a virus, bacterium or parasite. The most common cause in children is rotavirus, a “stomach bug”. Viral infections normally get better without treatment, but bacterial and parasitic infections may be treated with medication. Other causes of diarrhoea include stress, medications and conditions such as irritable bowel syndrome.
Diphtheria
Diptheria is an infectious disease caused by the Corynebacterium diphtheria bacterium. The bacteria usually infect the throat, although they can infect the skin as well. Symptoms include fever, sore throat, difficulty breathing and swallowing, and a grey membrane (“skin”) sticking to the tonsils and throat.
The infection may lead to life-threatening complications such as inflammation (swelling) of the heart muscle and nerve damage. Today diphtheria is very rare in the developed world because of vaccination, but it still causes more than 2000 deaths a year worldwide.
Down's syndrome
Every cell in your body carries your own unique set of coded instructions. The instructions, called genes, are found in two sets of 23 chromosomes inside the nucleus of body cells. Down’s syndrome occurs when there is an extra copy of chromosome 21. It is a genetic disorder, one passed down from one generation to the next.
People born with Down’s syndrome have particular facial characteristics and a greater risk of health problems, such as heart disease. They have mild to moderate learning difficulties. Although they need extra support, many attend mainstream schools and take up paid work as adults. The syndrome is named after John Langdon Down (1828–96), the British doctor who first described it.
Dysentery
Dysentery is inflammation (swelling) of the intestine, especially of the colon. This results in severe diarrhoea as well as stomach cramps. The disease can be caused by several types of bacteria, virus and parasite. The most common form of dysentery is bacillary dysentery, which causes mild gut pains and diarrhoea. Symptoms normally last no more than a week. Amoebic dysentery, which is caused by an amoeba (a single-celled parasite), is mainly found in tropical areas. Proper treatment of amoebic dysentery, using medication, is important, since it can remain dormant (inactive) for years and lead to severe complications.
Both bacillary and amoebic dysentery are highly infectious and can be passed on if the faeces (waste) of an infected person gets into another person's mouth. This can happen if someone with the infection does not wash their hands after going to the toilet and then touches food, surfaces or another person. In developing countries with poor sanitation, infected faeces may contaminate the water supply or food—particularly uncooked fruit, vegetables and salads.
E. coli
E. coli (called Escherichia coli in full) is a bacterium. Most types of the bacterium live harmlessly in the lower intestine of humans and animals such as cows, sheep and goats. However, some types, such as E. coli O157, are a cause of food poisoning, resulting in severe vomiting and diarrhoea (which is often bloody). Sometimes E. coli infection leads to complications such as kidney failure. E. coli infections are spread by eating food or drinking water that has come into contact with the faeces (waste) of people or animals infected with the bacteria. Some people have been infected when they fail to wash their hands after contact with farm animals.
Eating disorders
Eating disorders such as anorexia nervosa and bulimia nervosa are serious mental health conditions. People with anorexia are anxious about their weight and keep it as low as possible through limiting what they eat. They often also exercise excessively to lose weight. People who have bulimia are also anxious about their weight. They may "binge eat"—eat a lot of food in a short space of time—before trying to get rid of it ("purging") as quickly as possible by vomiting or using laxatives (medication that causes the bowels to empty). They usually do this in secret because they are ashamed of their behaviour.
Most cases of anorexia and bulimia develop in teenage girls and women, although both disorders also affect men. The causes are unknown, but probably result from a mix of biological and psychological factors. Long-term malnutrition resulting from these eating disorders can cause a range of serious complications. Treatment usually involve talking therapies (talking about feelings and behaviour). It can sometimes be difficult for a person to recognize that they have an eating disorder. It may be noticed by their friends and family, who can seek medical help for them.
Ebola
Ebola is a disease caused by infection with a virus in the ebolavirus group. The disease is spread by contact through broken skin, the mouth or nose with the blood, saliva, mucus, vomit, sweat, faeces and other body fluids of an infected person. Frequent hand-washing and good sanitation may help prevent infection. The first symptoms of Ebola, which appear two to 21 days after infection, include fever, sore throat and muscle pain, followed later by vomiting, rash and bleeding.
Ebola kills around half of infected people. No proven treatment or vaccination has yet been developed, but infected people should be cared for in hospital so they can be kept hydrated and isolated. The disease is usually seen in tropical regions of Africa. The largest outbreak is the 2014-15 West Africa epidemic, which by the end of that year had caused around 7000 deaths.
Eczema
Eczema is a skin condition that is particularly common in childhood. The key symptom is itchy patches of skin, which may be red, swollen, cracking, blistering or bleeding. Scratching may open up the skin and spread the rash. The causes of eczema are not fully known, and treatment is aimed at soothing the symptoms. Sufferers should avoid substances that can irritate the skin (such as bath bubbles and wool clothing), use a moisturizing cream daily and apply a steroid cream when the symptoms are severe.
Endometriosis
Endometriosis is a condition in women where tissue similar to the lining of the womb (uterus) starts to grow in other places, such as the ovaries, fallopian tubes, bladder and bowel. Like the womb lining, the tissue builds up and bleeds every month, but because there is no way for the blood to escape the body, it gets trapped, leading to inflammation. Endometriosis can affect women of any age, including young girls aged as young as 8. Symptoms may include severe pain in the abdomen, pelvis or lower back, especially during menstruation. Some have no symptoms at all.
The cause of endometriosis is not known. The condition can only be confirmed with a surgical examination called a laparoscopy (keyhole surgery). There is currently no cure for endometriosis, but there are treatments that can help ease the symptoms, including painkillers, hormone medication and surgery to cut away patches of endometriosis tissue.
Epilepsy
Epilepsy is a disorder of the body’s nervous system. There are several forms, all involving seizures—when a group of neurons in the brain begin firing all at once. Seizures may cause uncontrolled shaking or brief loss of awareness. Some seizures are brought on by “triggers” such as flashing lights, but many sufferers can have seizures at any time. It is often not known why a person develops epilepsy. Sometimes it may be the result of a head injury, stroke or infection, or the disorder may be passed down through a person's genes. Epilepsy cannot usually be cured, but seizures can often be controlled by medication.
Flu
See Influenza below
Food poisoning
Food poisoning is an illness caused by eating food that is spoiled, contains toxins, or contains bacteria, viruses or parasites. Symptoms include nausea (feeling sick), vomiting, diarrhoea and stomach pains. Most people get better on their own without needing treatment. This may be treated by drinking more water and other liquids than usual, or the person may need to drink a special rehydration solution (water containing sugar and salts). More serious symptoms may be seen if a toxin enters the bloodstream or if the body cannot quickly get rid of the bacteria, virus or parasite. In developed countries, the most common causes are salmonella, campylobacter, clostridium botulinum (causing botulism) and listeria (all bacteria), and the norovirus.
Gallstones
Gallstones are hard “stones” that can form in the gall bladder. The gall bladder is a hollow organ where bile (gall) is stored before being released into the small intestine to help with digestion. Gallstones usually form because there is too much cholesterol in the bile, and the excess solidifies to form stones. Gallstones are more common in women, people over 40 and people who are overweight. Around 1 in 10 adults have them but may not realise it unless the stones cause inflammation or get trapped in the opening of the gall bladder. These complications cause severe pain and are often treated by removing the gall bladder entirely.
Gastroenteritis
Gastroenteritis is a condition when the stomach and intestines become inflamed (swollen and sore). It is usually the result of an infection of the intestines, caused by a virus, bacterium or parasite. Symptoms include diarrhoea, vomiting and stomach pain. In developed countries, the most common causes of gastroenteritis are viruses, such as rotavirus and norovirus, and food poisoning.
Gastroenteritis caused by a virus will normally get better without treatment, but bacterial and parasitic infections may be treated with medication. If diarrhoea and vomiting go on for too long, they can cause dehydration (loss of body water). This may be treated by drinking more water and other liquids than usual, or the person may need to drink a special rehydration solution (water containing sugar and salts).
Glaucoma
Glaucoma is an eye condition where the optic nerve, which connects the eye to the brain, is damaged. This is usually because of too much pressure within the eye. The eye constantly makes a fluid called aqueous humour, which gives the eyeball its shape. But if the eye’s drainage tubes become blocked, too much pressure can build up. If not treated, glaucoma can cause blindness.
There are four main types of glaucoma, the most common being chronic open-angle glaucoma, which is most often seen in people aged over 75. Regular eye checks are needed to spot glaucoma early. Eye drops, medication, laser treatment and surgery can prevent further loss of sight.
Haemophilia
Haemophilia is a rare genetic disorder that stops a person’s blood from clotting properly. Normally, when someone cuts themselves, substances in the blood, called clotting factors, combine with fragments of blood cells, called platelets, to seal the wound. A person with haemophilia does not have enough clotting factors in their blood, so they will bleed for much longer. Injections of the clotting factor that is missing from the blood are an effective treatment. Haemophilia is passed down in a person’s genes. Although girls can carry the gene for haemophilia, the disorder usually occurs in boys.
Heart disease
The most common form of heart disease is coronary heart disease. It is the world’s leading cause of death: around 1 in 5 men and 1 in 8 women die from it. Coronary heart disease is when the heart’s blood supply is blocked by fatty deposits in the coronary arteries, the vessels that supply oxygen-rich blood to the heart. Older adults are more likely to suffer from coronary heart disease. This condition is also more common in people who have high blood pressure, diabetes or a high blood chlolesterol level. Being overweight, smoking and not taking enough exercise also increases a person's risk of coronary heart disease. Coronary heart disease can cause angina (chest pain), heart attacks (when the blood supply to the heart is briefly cut off, injuring the heart muscle) and heart failure.
Heart disease may be prevented by better diet, stopping smoking and taking more exercise. Treatment is by medication and, possibly, heart surgery. Other forms of heart disease, which have a range of causes, include cardiomyopathy, which affects the heart muscle’s ability to pump, cardiac dysrhythmia (uneven heartbeat) and endocarditis, the swelling of the inner layer of the heart.
Hepatitis
Hepatitis is the condition of having an inflamed (swollen) liver. The liver processes blood from the digestive system, makes substances needed by the body's cells and removes poisons and waste from the blood. Mild hepatitis may have few symptoms and heal by itself. Severe hepatitis will yellow the skin and whites of the eyes. It can scar the liver and stop it doing its work.
Hepatitis is most often caused by a hepatitis virus, called types A, B, C, D and E. They are caught in different ways, including by eating infected food, injecting illegal drugs or having unprotected sexual intercourse. Hepatitis may also be caused by the effects of certain other diseases, and eating or drinking large amounts of damaging substances, such as alcohol and certain medications.
Hernia
A hernia is when an internal part of the body slips through the wall of muscle and tissue that normally holds it. The most common place for a hernia is the abdomen (between your chest and hips), where fatty tissue or part of an organ, such as the bowel, can stick out through a weak spot in the muscle. A hernia is covered by a layer of skin and body fat, but it can cause a lump and may be painful. A hiatus hernia is when the stomach sticks into the chest cavity. Hernias are often caused by ageing or muscle strain. A severe hernia may need to be repaired with surgery. If a hernia becomes strangulated (when the blood supply to the trapped tissue or organ becomes cut off) or is blocking the bowel’s movements, it needs treating urgently.
HIV/AIDS
AIDS (Acquired ImmunoDeficiency Syndrome) is a disease of the immune system, which is the body’s defence against disease. AIDS is caused by infection with the Human Immunodeficiency Virus (HIV). The disease is usually called HIV/AIDS, to cover its entire course from first infection to late symptoms. As the disease develops, it interferes more and more with the immune system, so the person will suffer a growing number of infections and tumours.
There is not yet a cure for HIV/AIDS, but antiretroviral drugs can slow its course, so infected people can have close to normal life expectancies. Since the disease was identified in the early 1980s, it has caused 39 million deaths worldwide. The disease is spread through unprotected sexual intercourse, infected blood transfusions and hypodermic needles, and sometimes from mother to child during pregnancy and breastfeeding.
Huntington's disease
Huntington's disease is a genetic condition that damages certain nerve cells (neurons) in the brain. As the brain damage gradually worsens over the years, a person's movement, thinking, mood and behaviour are affected. Huntington's disease was originally called Huntington's chorea (chorea is the Greek word for dancing). This is because the involuntary movements caused with the condition can look like jerky dancing.
Huntington's disease is caused by a faulty gene. There is no cure and the disease's progress cannot be slowed down. Medicines aim to manage some of the symptoms. Physiotherapy and occupational therapy can help with movement problems and difficulties with day-to-day living.
Influenza
Often called flu, influenza is a disease caused by influenzaviruses. These can infect humans, other mammals and birds. The viruses are usually spread through the air by coughing and sneezing, by touching nose mucus and by touching contaminated objects. Influenza is often confused with the common cold, but it is more severe. Its symptoms include: fever, tiredness, muscle aches, headache, runny nose, sore throat, coughing and, possibly, vomiting and diarrhoea. Flu can lead to complications such as pneumonia and bronchitis.
Flu spreads in yearly epidemics (widespread infection in a community), usually in autumn and winter. Sometimes pandemics (widespread infection throughout a country or the world) occur, such as the 1918 Spanish flu and the 2009 swine flu pandemics. In developed countries, vaccinations to protect against flu are often available.
Leprosy
Leprosy is a disease that affects the skin and nerves. It is caused by the bacteria Mycobacterium leprae. Leprosy is spread by droplets from the nose and mouth of untreated patients, but it is not highly infectious. If not treated, the disease will eventually damage the nerves so badly that feeling is lost. This may cause injuries to go unnoticed, resulting in infections and disability.
Leprosy is treated by a course of medication. Today it is rare. Around half the world’s new leprosy cases are in India, where there are about 140,000 a year.
Leukaemia
Leukaemia is a cancer that begins in bone marrow, the tissue inside bones. Bone marrow contains stem cells, which manufacture the body’s blood cells. Leukaemia causes large numbers of abnormal white blood cells, called blasts, to be made. Blasts cannot fight infection as healthy white blood cells do. Too many blasts in the blood leads to fewer red blood cells and platelets, which help the blood to clot.
Leukaemia can be treated with a bone marrow transplant, in which damaged bone marrow is replaced with healthy stem cells, and chemotherapy, radiation therapy and targeted therapy, all of which kill the blasts. Leukaemia is rare, but it is the most common childhood cancer. Today, the chances of a cure are very good.
Lyme disease
Lyme disease, or Lyme borreliosis, is a bacterial infection that is spread to humans by infected ticks. Ticks, tiny spider-like animals, are found in woodland and heathland. They feed on the blood of birds and mammals, including humans. A few days after being bitten, many people develop a large circular rash—looking like a bull's-eye on a dart board—at the site of the tick bite, which gradually expands. This is known as erythema migrans. However, not everyone will not develop this rash. Some people with Lyme disease also experience flu-like symptoms in the early stages, such as tiredness, muscle or joint pain, headaches and fever.
Lyme disease can usually be treated easily with antibiotics if it is detected early. Later-stage symptoms are more serious, including pain and swelling in the joints, paralysis of the facial muscles, heart palpitations and severe headaches, for which a more intense course of antibiotics is needed.
Lymphoma
Lymphoma is the name given to a number of blood cancers that develop from lymphocytes (types of white blood cell). Symptoms include painless swollen lymph nodes, fever, weight loss and constant tiredness. The two main types are Hodgkin's lymphoma (HL) and non-Hodgkin lymphoma (NHL). Lymphoma most often spreads from the lymph vessels to the lungs, liver and brain. The affected lymphocytes lose their infection-fighting properties, making the person with lymphoma more vulnerable to infection.
The cause of lymphoma is not known, but the risk of getting it is higher if the immune system is weakened. Treatment may involve chemotherapy, radiation therapy or surgery. In children, lymphoma is the third-most common cancer. Nowadays, most people survive to lead normal lives.
Malaria
Malaria is a disease spread by mosquitoes in the world’s tropical and subtropical regions. There are more than 200 million cases a year, causing over 500,000 deaths—many of them children. If a female Anopheles mosquito bites a human infected with malaria, she can carry the malaria-causing parasites, called Plasmodium, to other people that she bites. The parasites then travel to the human liver, where they reproduce. Severe malaria can cause fever, vomiting, headache, yellow skin, coma (lengthy unconsciousness) and death.
Malaria can be treated with anti-malaria medications. It can also be prevented by sleeping under a mosquito net, wearing insect repellant and by spraying insecticides. In Africa alone, these interventions are estimated to have prevented 663 million malaria cases between 2000 and 2015. However, these methods are not widely available in the world’s poorest regions. In October 2021, the World Health Organization announced that, following successful trials, the world's first malaria vaccine, called RTS,S or Mosquirix, will made available to children across sub-Saharan Africa where the vast majority of cases and deaths occur. It will be given along with anti-malarial medication.
Measles
Measles is an infection of the respiratory system (lungs and airways) by a virus in the paramyxovirus family. It is very infectious and is spread by droplets from an infected person’s nose and mouth, either through coughs and sneezes or by direct contact. Symptoms include fever, greyish spots in the mouth, runny nose, red eyes and, after two or three days, a spotty rash over most of the body.
Measles can lead to very serious complications, such as bacterial infections of the lungs and brain. Between 2000 and 2013, deaths from measles around the world dipped by 78% because of widespread vaccination. There are still 120,000 deaths a year among those who have not been vaccinated. Measles is one of the leading causes of death among young children across the world.
Meningitis
Meningitis is the inflammation (swelling) of the membranes that protect the brain and spinal cord, the meninges. It is most often caused by infection by bacteria or viruses, but may occasionally be caused by fungi or parasites. Meningitis usually needs to be treated quickly as it can damage the brain and infect the blood (sepsis).
The commonest symptoms are: headache, stiff neck, fever, confusion and an inability to look at bright light. Small children may just be drowsy or irritable, but their hands and feet may be cold and their skin pale and blotchy. In a serious form of meningitis caused by meningococcal bacteria (Neisseria meningitidis) there is usually a rash. There are purple or red spots that do not fade when a glass is rolled over them. Childhood vaccinations with the meningitis C, Hib, MMR and pneumococcal vaccines can protect against many serious forms of meningitis.
Motor neuron disease
Motor neurons are cells in the brain and spinal cord that control important muscle activity, including walking, speaking, breathing and swallowing. The disease stops these cells from working properly, making it harder and harder for a person to perform these essential activities. There is no cure for motor neuron disease and its causes are not fully known, but it is very rare.
Multiple sclerosis
The nerve fibres in the brain and spinal cord are protected by a layer of protein called myelin. Multiple sclerosis, often called MS, is a disease that damages this layer, which has the effect of preventing nerve signals from being passed on properly. The disease causes problems with muscle movement, balance and vision, which get worse over time. MS is caused by the body’s immune system attacking the myelin, although why this happens is not fully understood. There is no cure for MS but a range of medications and therapies can help ease the symptoms.
Mumps
Mumps is an infection caused by the mumps virus. Symptoms include: a painful swelling of the parotid glands, where saliva is made, giving a “hamster-like” appearance; fever; headache; joint pain. Most cases of mumps get better within two weeks, but sometimes the infection leads to serious complications, such as meningitis and hearing loss. Teenage boys and men may have painful swelling of the testicles if they catch the virus. A vaccine against mumps is widely given to young children in the developed world.
Osteoporosis
Osteoporosis is a condition that weakens the bones, making them more likely to break. It develops slowly over several years, and is often only diagnosed when a minor fall causes a bone fracture. Osteoporosis becomes more common with age. A sign of osteoporosis in some older people is their stooped (bent forward) posture. This happens when the bones in the spine fracture, making it hard to support the body's weight.
Losing bone happens to everyone as they age, but in some people bone density is lost much faster than normal. This happens in women in the first few years after the menopause (when monthly periods stop and the ovaries stop producing eggs). Prevention of osteoporosis includes a good diet during childhood. Efforts to avoid broken bones include healthy eating, exercise and fall prevention. Medications to strengthen bones can also help.
Parkinson’s disease
Named after the English doctor James Parkinson (1755–1824), Parkinson’s disease is caused by the loss of particular nerve cells in part of the brain called the substantia nigra. These nerve cells make dopamine, a hormone that helps the body to control movement. Without enough dopamine, people with Parkinson’s disease will have tremors, stiff muscles and slow movements. These symptoms get worse over time. Problems with thinking and emotions may also appear. Parkinson’s disease does not cause death, but it can make the body more at risk of infection.
Most people diagnosed with Parkinson’s disease are over 50 years old. There is not yet a cure for the disease, but medications and physical therapy can help with symptoms.
Peptic ulcer
A peptic ulcer is an open sore in the lining of the stomach, when it is called a stomach or gastric ulcer, or the first part of the small intestine, when it is called a duodenal ulcer. The stomach produces acid to digest food. The lining of the stomach and small intestine is coated with mucus to protect against the acid. If a person’s intestines become infected with Helicobacter pylori bacteria or they take too many anti-inflammatory drugs, such as aspirin and ibuprofen, the mucus can be broken down, allowing the acid to cause damage. Ulcers are usually treated with medication to cut down acid in the digestive system, alongside antibiotics if it is Helicobacter pylori causing the problem.
Pneumonia
Pneumonia is the inflammation (swelling) of the tissue in one or both lungs. The lung’s tiny air sacs, called alveoli, fill up with fluid. This causes difficulty breathing, fever and a cough, which may bring up thick, coloured mucus. Pneumonia is caused by infection with bacteria, often Streptococcus pneumoniae, viruses such as those that cause colds and influenza, or sometimes by fungi, parasites and certain drugs and diseases. Treatment is with antibiotics, rest and fluids. Pneumonia is a major cause of death among people who are frail or elderly.
Polio
Polio, short for poliomyelitis, is a disease caused by the poliovirus. The virus is usually passed on by contact with the faeces (waste) of an infected person or by eating food or drinking water that is infected. The virus invades the intestines, from where it can enter the bloodstream or the nervous system. If it enters the nervous system it can cause paralysis. There is no cure or treatment for polio, but it can be prevented by vaccination. Worldwide vaccination programmes since the 1950s has almost succeeded in wiping out the disease. However, there have been outbreaks of polio in Afghanistan and Pakistan.
River blindness
Onchocerciasis, also known as river blindness, is a disease caused by infection with a certain species of parasitic worm. This is spread by the bites of a type of blackfly that lives near rivers in the tropics, hence the common name of the disease. Once inside the body, the worms give birth to larvae that collect under the skin. Here they can infect the next blackfly that bites the person. Symptoms of river blindness include severe itching, bumps under the skin and blindness. About 15.5 million people are infected with river blindness, most of whom live in sub-Saharan Africa. There is no vaccine against the disease, so avoiding being bitten by flies is the only way to prevent infection. Efforts to eradicate river blindness involve treating large groups of people by killing the larvae.
Rubella
Rubella, also known as German measles, is a disease caused by the rubella virus. It is usually passed on in droplets of moisture from the nose or throat of an infected person. Symptoms of rubella infection include a rash, low fever and swollen glands. The disease is usually mild and gets better without treatment within a few days. However, if a pregnant woman catches the disease, it can harm her baby. For that reason, a vaccination is given to children in the developed world as part of the MMR (Measles/Mumps/Rubella) vaccine.
Schistosomiasis
Schistosomiasis, also known as snail fever and bilharzia, is a disease caused by parasitic flatworms called schistosomes. It is spread by contact with fresh water contaminated with the parasites, which are released into the water from infected freshwater snails. The disease is especially common among children in developing countries, as they are more likely to play in contaminated water. Symptoms include abdominal pain, diarrhoea and blood in the urine or stools. In children, schistosomiasis may cause poor growth and learning difficulties. Those who have been infected for a long time may suffer more serious conditions such as liver damage, kidney failure or bladder cancer.
A tropical disease, schistosomiasis is most commonly found in sub-Saharan Africa, Asia and South America. Ways of preventing it include improving access to clean water and culling the snails. In areas where the disease is common, medication may be given once a year to the entire population. This decreases the number of people infected and so limits the spread of the disease.
Sepsis and septic shock
Sepsis can be triggered by an infection—usually bacterial—in any part of the body. Infections of the lungs (pneumonia), abdomen (peritonitis), kidneys and urinary tract or bloodstream are most likely to cause sepsis. Usually the body's defences can fight off the infection and prevent it from spreading. Swelling, known as inflammation, takes place close to the infection, while white blood cells are summoned by the immune system to destroy the invading pathogens. But if the immune system is weak or the infection particularly severe, the infection may quickly spread through the blood into other parts of the body, causing inflammation to affect the entire body. Treatment involves medication to increase blood pressure and antibiotics to kill the bacteria.
Severe cases of sepsis can lead to septic shock. This happens when toxins (poisons) produced by the bacteria start to damage the blood vessels. This affects the heart's ability to pump blood to the organs, reducing blood pressure, causing dizziness and vomiting. Low pressure means the blood cannot reach vital organs, such as the brain or liver, so emergency treatment is required.
Sleeping sickness
African trypanosomiasis, also known as sleeping sickness, is a caused by certain species of protozoa and transmitted by the bite of an infected tsetse fly. It is most common in rural areas of sub-Saharan Africa, and also affects animals. In the first stage of the disease, the victim suffers fevers, headaches, itchiness and joint pains. Some weeks later, second stage symptoms—confusion, poor co-ordination and difficulty sleeping—set in. Without treatment, requiring medication, the disease usually results in death. Trypanosomiasis may, in future, be prevented by genetically altering the tsetse fly, making it immune to the infection.
Smallpox
Smallpox was a disease caused by the viruses Variola major and Variola minor. Thanks to vaccination across the world, in 1980 the World Health Organization (WHO) declared that the disease had been wiped out. A major symptom of smallpox was a rash, which developed into blisters and usually led to scarring. Between 1900 to 1979, smallpox caused up to 500 million deaths.
Snake bites
A snake may bite in self-defence if it is disturbed or provoked, often when someone accidentally steps on it. Some snakes are venomous: they inject venom containing toxins as they bite. The bite can be deadly if not treated quickly. While awaiting emergency medical help, the part of the body that has been bitten should be kept as still as possible to prevent the venom from spreading. The victim should NOT try to suck or cut the venom out of the bite or put a tight pressure band around the bitten limb. Giving the healthcare professionals a description of the snake will help them identify it and supply the appropriate antivenom. This contains antibodies, proteins that counter the effects of the toxins in the snake's venom.
Symptoms of a venomous bite include: severe pain, swelling and bruising, feeling sick, diarrhoea, bleeding, dizziness, faintness and muscle paralysis, which can lead to breathing difficulties. In a small number of people, a snake bite can trigger a severe reaction, known as anaphylaxis. Someone who has been bitten by a snake may go into shock, a life-threatening condition that occurs when there is an insufficient supply of oxygen to the body.
Strep A
Group A Streptococcus (GAS), also known as Strep A, is a common type of bacterium, found on the skin or in the throat. In some circumstances Strep A bacteria can cause disease. It can be spread through coughs, sneezes and skin-to-skin contact. Those carrying the bacteria may have no symptoms, but are just as likely to pass on Strep A as those who have fallen ill. Infections are mild and easily treated, but some are more serious. Common symptoms include: high temperature, swollen glands, sore throat ("strep throat"), a rash that feels rough (scarlet fever), sores and blisters on the skin (impetigo), pain and swelling (cellulitis), severe muscle aches, nausea and vomiting. Strep A infections are more common in children, and most can be treated with antibiotics.
If the bacteria enter the bloodstream an infection can become severe and life-threatening. A very rare disease, this is called invasive group A strep GAS (iGAS).
Stroke
A stroke occurs when the blood supply to part of the brain is cut off. Without blood, brain cells can be destroyed, so strokes need to be treated immediately. Symptoms include the face drooping to one side, being unable to lift one or both arms and the speech slurred, garbled, or being unable to speak at all.
There are two main causes of strokes: a blood clot stopping the blood supply to the brain, and the bursting of a blood vessel that supplies part of the brain. People aged over 65 are most at risk from strokes, especially if they have high blood pressure (hypertension). Treatment includes medicines to remove blood clots and surgery to repair damage. After a stroke, therapy is often needed to help with movement, speech, memory or emotions.
Tetanus
Tetanus is an infection caused by the bacterium Clostridium tetani, which is found in soil, dust and animal and human faeces. Infection is usually through a wound or burn to the skin. Inside the body, the bacteria make a poison, called a neurotoxin, which causes muscle stiffness and spasms—often in the jaw, hence the name "lockjaw"—and difficulty swallowing. In the developed world, children are usually given a course of vaccinations to protect against it.
Tonsillitis
The tonsils are two small glands that sit on either side of the throat. In young children, they help to fight germs. When they become infected, the tonsils stop the infection spreading further into the body. As the child's immune system develops, tonsils become less important and shrink.
Tonsillitis is the inflammation (swelling) of the tonsils. A common condition in children, teenagers and young adults, it is usually caused by a viral infection, but is sometimes the result of a bacterial infection. Symptoms of tonsillitis include: a sore throat and pain when swallowing, earache and fever. It usually clears up after a few days without requiring treatment, although if the tonsillitis is caused by a bacterial infection, antibiotics will help treat it. If the condition lasts longer, or keeps returning, removal of the tonsils may be needed.
Tuberculosis
Often called TB, tuberculosis is a disease caused by certain bacteria, usually Mycobacteria tuberculosis. The bacteria usually affect the lungs, causing coughing—sometimes bringing up blood—chest pain and weight loss. However, other body parts can be affected, including the bones and nervous system.
About one-third of the world’s population is infected with Mycobacteria tuberculosis, mostly in the developing world, although only in around one in ten infected people will the disease become "active". If untreated, more than half of people with active tuberculosis would die. The bacteria are spread by the coughs and sneezes of people with active tuberculosis. Treatment is with antibiotics; vaccination against tuberculosis is widely available.
Typhoid
Typhoid is a disease caused by infection with the Salmonella typhi bacterium. The disease is spread by eating food, drinking water or touching objects contaminated with the faeces of an infected person. Today, the disease is rare in countries with good sanitation and clean drinking water, but outbreaks are common in parts of Southeast Asia and sub-Saharan Africa. Early symptoms include fever, stomach pain, constipation or diarrhoea, headache and confusion. If not treated quickly, the infection can lead to life-threatening complications such as internal bleeding. Treatment is with antibiotics to kill the bacteria.
Typhus
Typhus—a completely different disease to typhoid—is caused by the Rickettsiae bacteria. It is spread by fleas, mites, lice and ticks that carry the bacteria. These pick up the bacteria when they bite an infected person. They pass the bacteria on through their faeces, which they leave on a person's skin while they are biting. Scratching the area opens up the skin, allowing the bacteria from the faeces to enter the bloodstream where they spread throughout the body.
Typhus often breaks out where people are forced to live together in confined spaces in unhygienic conditions. Common symptoms include headaches, fever, chills and a rash. Untreated typhus can be life-threatening. Antibiotics can stop the infection, but it can be prevented by eliminating the creatures that spread it with pesticides.
Whooping cough
Also called pertussis, whooping cough is an infection of the lungs and airways by the Bordetella pertussis bacterium. The infection is easily spread by the coughs and sneezes of infected people. The bacteria cause a build-up of thick mucus in the airways, leading to spasms of intense coughing, and swollen airways, which makes breathing difficult. People with whooping cough often make a “whoop” sound as they gasp for breath after coughing. Whooping cough can sometimes lead to complications, such as pneumonia and damage to other body organs. Treatment is with antibiotics to kill the bacteria. A whooping cough vaccine is part of the childhood vaccination programme in most developed countries.
Yellow fever
Yellow fever is caused by a virus and is spread by the bite of an infected female mosquito. A disease of the tropics and sub-tropics, it occurs in parts of sub-Saharan Africa, South America, Central America and the Caribbean. Symptoms include fever, aching and vomiting. Simple painkillers may help reduce pain and bring down a person’s temperature. The disease may be difficult to tell apart from other illnesses, especially in the early stages. Most people make a full recovery after a few days, but a few develop more serious symptoms, such as a yellowing of the skin and eyes (known as jaundice), bleeding from the mouth, nose or eyes, and vomiting blood, which can lead to death. A safe and effective vaccine against yellow fever exists.
Consultant: Kristina Routh