Disease information

Explore disease information, including symptoms, transmission, prevention, diagnosis and care, with links to the original sources.

Adenovirus infection
Adenoviruses are a group of common viruses that can affect the airways, eyes or gut. They infect people of all ages throughout the year. Most infections are mild, but pneumonia and other…
Anthrax
Anthrax is a serious bacterial infection associated mainly with infected animals or contaminated animal products. The bacteria form spores that can survive in soil. Illness depends on…
Chikungunya
Chikungunya is a viral infection spread mainly by mosquitoes in tropical and subtropical areas. It often causes a sudden fever and pronounced joint pain. Most people recover from the…
Cholera
Cholera is a bacterial infection of the gut, usually acquired from contaminated food or drinking water. Many infections cause no symptoms or only mild illness. Severe cases produce very…
COVID-19
COVID-19 is an infection caused by the SARS-CoV-2 virus. It circulates worldwide and can range from an infection without symptoms to severe illness. Older adults, pregnant people and…
Dengue
Dengue is a mosquito-borne viral infection found mainly in tropical and subtropical regions. Many infections are mild or have no symptoms, but some become severe. Having had dengue…
Diphtheria
Diphtheria is an infection caused by bacteria that produce a harmful toxin. It can affect the nose and throat or cause skin sores. In respiratory diphtheria, a thick coating can block…
Ebola virus disease
Ebola disease is a serious viral illness caused by a group of related viruses found mainly in sub-Saharan Africa. It can progress from fever and tiredness to severe illness. Ordinary…
Haemophilus influenzae type b
Haemophilus influenzae type b (Hib) is a bacterium that can cause serious infections, particularly in young children. These include meningitis, bloodstream infection, pneumonia and…
Hantavirus
Hantaviruses are a group of viruses carried mainly by rodents. Different types can cause serious disease affecting the lungs or kidneys. Lung disease occurs mainly in the Americas, while…
Hepatitis A
Hepatitis A is a viral infection that inflames the liver. Young children may have few or no symptoms, while older children and adults are more likely to feel unwell. Most people recover,…
Hepatitis B
Hepatitis B is a viral liver infection that can be short-lived or become chronic. Many people have no symptoms, including those with long-term infection. Chronic infection can eventually…
Herpes zoster
Shingles (herpes zoster) occurs when the virus that previously caused chickenpox becomes active again in the body. It usually causes a painful rash on one side of the body. Risk…
Human papillomavirus
Human papillomavirus (HPV) is a common group of viruses spread through intimate contact. Most infections clear without causing health problems. Some types cause genital warts, while…
Influenza
Influenza (flu) is a respiratory infection caused mainly by influenza A and B viruses. It often starts suddenly and can feel much more intense than a common cold. Most people recover,…
Japanese encephalitis
Japanese encephalitis is a mosquito-borne viral infection found in parts of Asia and the western Pacific. Most infections cause no symptoms. A small proportion cause inflammation of the…
Leishmaniasis
Leishmaniasis is an infection caused by parasites spread by sand flies. Different forms affect the skin, the lining of the nose and mouth, or internal organs. Skin disease may leave…
Leptospirosis
Leptospirosis is a bacterial infection linked to the urine of infected animals, including rodents. It occurs worldwide, particularly in tropical areas and after heavy rain or flooding.…
Malaria
Malaria is a parasitic infection spread mainly by mosquitoes. It occurs in parts of Africa, Asia, the Americas and the Pacific. Risk varies substantially within countries and with…
Measles
Measles is a highly contagious viral infection. It can cause serious complications, including pneumonia and inflammation of the brain, especially in young children and other vulnerable…
Meningococcal disease
Meningococcal disease is a bacterial infection that can cause meningitis, affecting the lining around the brain and spinal cord, or a dangerous bloodstream infection. It can worsen…
Mpox
Mpox is a viral illness that often causes a painful rash and swollen lymph nodes. Most people recover, but severe illness can occur, particularly in young children, pregnant people and…
Mumps
Mumps is a contagious viral infection that commonly causes swelling of the saliva-producing glands near the ears. It can affect children and adults. Most people recover fully, but…
Norovirus
Norovirus is a highly contagious virus that causes sudden inflammation of the stomach and intestines. It is sometimes called stomach flu, but it is unrelated to influenza. Most people…
Pertussis
Pertussis, or whooping cough, is a very contagious bacterial infection of the airways. It may begin like a cold, then develop into repeated coughing fits that can continue for weeks or…
Pneumococcal disease
Pneumococcal disease refers to infections caused by pneumococcus bacteria. These bacteria can cause ear or sinus infections, but also pneumonia, bloodstream infection, or meningitis, an…
Polio
Polio is an infection caused by poliovirus. Most infected people have no visible symptoms, while some develop a brief flu-like illness. In a small proportion, the virus affects the…
Rabies
Rabies is a viral infection that attacks the nervous system. It is almost always fatal once symptoms begin, but prompt treatment after an exposure can prevent the disease. Symptoms may…
Respiratory syncytial virus
Respiratory syncytial virus, or RSV, is a common virus that infects the airways and lungs. Most infections resemble a cold, but RSV can cause inflammation of the small airways or…
Rickettsial diseases
Rickettsial diseases are a group of bacterial infections that include spotted fevers and typhus. Many are acquired from ticks, fleas, mites, or lice. Some cause a relatively mild…
Rotavirus
Rotavirus is a contagious virus that causes vomiting and diarrhea, especially in babies and young children. The main danger is dehydration from losing too much fluid. Older children and…
Rubella
Rubella is a contagious viral infection, sometimes called German measles, but it is different from measles. It is often mild or causes no symptoms. Its greatest danger is during…
Schistosomiasis
Schistosomiasis, also called bilharzia, is an infection caused by parasitic worms. Larvae in contaminated freshwater enter through the skin. Some people have no symptoms, but untreated…
Smallpox
Smallpox was a serious contagious illness caused by variola virus. It has been eradicated: there is no ongoing natural transmission. Vaccination was central to ending the disease. This…
Tetanus
Tetanus is a serious bacterial disease acquired when spores from the environment enter damaged skin. It causes painful muscle stiffness and spasms and can interfere with swallowing or…
Tick-borne encephalitis
Tick-borne encephalitis, or TBE, is a viral infection that can affect the brain and the tissues around the brain and spinal cord. Many infections cause no symptoms. Some begin as a…
Tuberculosis
Tuberculosis, or TB, is a bacterial infection that most often affects the lungs but can involve other organs. Many infected people have latent TB: the bacteria remain inactive, without…
Typhoid fever
Typhoid fever is a bacterial infection caused by Salmonella Typhi. Unlike many short-lived stomach infections, it can cause a prolonged illness throughout the body and serious…
Varicella
Chickenpox, or varicella, is a highly contagious infection caused by varicella-zoster virus. It typically causes an itchy blistering rash. Although many people recover without major…
Yellow fever
Yellow fever is a mosquito-borne viral infection. Many infections cause little or no illness, but some progress to a severe form that damages the liver and other organs. Yellowing of the…
Zika
Zika is a viral infection mainly spread by mosquitoes. Many people have no symptoms, and illness is usually mild when symptoms occur. Infection during pregnancy can nevertheless…