Diseases & Conditions

Research to understand and treat some of the world's most problematic diseases

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Allergic Diseases | Immunologic Diseases | Infectious Diseases

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Asthma

Asthma is a chronic lung disease characterized by episodes of airway narrowing and obstruction, causing wheezing, coughing, chest tightness and shortness of breath.

Healthy Human T Cell

Autoimmune Diseases

More than 80 diseases occur as a result of the immune system attacking the body’s own organs, tissues, and cells. Some of the more common autoimmune diseases include type 1 diabetes, rheumatoid arthritis, systemic lupus erythematosus, and inflammatory bowel disease.

Although the causes of many autoimmune diseases remain unknown, a person’s genes in combination with infections and other environmental exposures are likely to play a significant role in disease development. Treatments are available for many autoimmune diseases, but cures have yet to be discovered.

Illustration of fas protein.

Autoimmune Lymphoproliferative Syndrome (ALPS)

Autoimmune lymphoproliferative syndrome (ALPS) is a rare genetic disorder of the immune system first described by NIH scientists in the mid-1990s that affects both children and adults. In ALPS, unusually high numbers of white blood cells called lymphocytes accumulate in the lymph nodes, liver, and spleen and can lead to enlargement of these organs. ALPS can also cause anemia (low level of red blood cells), thrombocytopenia (low level of platelets), and neutropenia (low level of neutrophils, the most common type of white blood cell in humans).

Image of Vibrio cholerae

Cholera

Cholera is an acute, diarrheal illness caused by infection of the intestine with the bacterium Vibrio cholerae. An estimated 3-5 million cases and over 100,000 deaths occur each year around the world. The infection is often mild or without symptoms, but can sometimes be severe. Approximately one in 10 (5 to 10 percent) infected persons will have severe disease characterized by profuse watery diarrhea, vomiting, and leg cramps. In these people, rapid loss of body fluids leads to dehydration and shock. Without treatment, death can occur within hours.

A female Aedes aegypti mosquito ingesting a blood meal.

Dengue Fever

Dengue fever is an infectious disease carried by mosquitoes and caused by any of four related dengue viruses. This disease used to be called "break-bone" fever because it sometimes causes severe joint and muscle pain that feels like bones are breaking. Health experts have known about dengue fever for more than 200 years. 

Image of e. coli bacteria

E. coli

Escherichia coli (E. coli) bacteria live in the intestines of people and animals, and are key to a healthy intestinal tract. Most E. coli strains are harmless, but some can cause diarrhea through contact with contaminated food or water while other strains can cause urinary tract infections, respiratory illness and pneumonia.

Ebola Virus

Ebola & Marburg

Ebola virus disease, first recognized in 1976 in the Democratic Republic of the Congo, is a serious and often fatal illness in humans and nonhuman primates caused by infection with one of five Ebola virus species (four of which can infect humans). The virus is spread through direct contact with the bodily fluids of a sick person and can cause fever, headache, muscle pain, weakness, fatigue, diarrhea, vomiting, stomach pain and hemorrhage (severe bleeding).

Photo of young boy wrapped in towels sitting in a bathtub

Eczema (Atopic Dermatitis)

Atopic dermatitis, also known as eczema, is a non-contagious inflammatory skin condition. It is a chronic disease characterized by dry, itchy skin that can weep clear fluid when scratched. People with eczema also may be particularly susceptible to bacterial, viral, and fungal skin infections.

Food Allergy

NIAID is the lead Institute at the National Institutes of Health conducting research on food allergy, a condition that affects approximately 5 percent of children and 4 percent of adults in the United States. In a person with food allergy, the immune system reacts abnormally to a component of a food—sometimes producing a life-threatening response.

Scanning electron micrograph of phagocytosis of a dead yeast particle (zymosan)

Fungal Diseases

Fungal diseases are caused by a wide variety of fungi that are commonly found in the environment. Invasive fungal infections rarely occur in healthy people, but fungi can cause serious infections in individuals with weakened immune systems.

Photo of Neisseria gonorrhoeae bacteria

Gonorrhea

Gonorrhea is a sexually transmitted disease that can infect both men and women. Caused by the Neisseria gonorrhoeae bacterium, gonorrhea can cause infections in the genitals, rectum and throat. Although treatable, drug-resistant forms of gonorrhea are increasing.

Group A Streptococcus Bacteria on Human Neutrophil

Group A Streptococcal Infections

Group A streptococcal (GAS) infections can range from a mild skin infection or a sore throat to severe, life-threatening conditions. Most people are familiar with strep throat, which along with minor skin infections, is the most common form of the disease.

Photo of liver tissue specimen extracted from a viral hepatitis patient.

Hepatitis

Hepatitis is an inflammation of the liver. Viruses are the most common cause of hepatitis, but the condition can also be caused by other infections, heavy alcohol use, toxins, certain medications, and autoimmune disease. There are five main virus types that cause hepatitis---type A, B, C, D, and E. Hepatitis A and E are typically caused by ingesting contaminated food or water. Hepatitis B commonly occurs through contact with infected blood, semen or other bodily fluid through sex, sharing needles or other drug-injection equipment or from mother to baby at birth.

Scanning electromicrograph of an HIV-infected T cell.

HIV/AIDS

HIV, or human immunodeficiency virus, is the virus that causes AIDS (acquired immunodeficiency syndrome) and can be transmitted during sexual intercourse; by sharing syringes; or perinatally during pregnancy, childbirth or breastfeeding. Since the first AIDS cases were reported in 1981, HIV/AIDS has been one of humanity’s deadliest and most persistent epidemics. Although extraordinary progress has been made in the fight against new HIV cases and AIDS deaths, the HIV pandemic continues.

Influenza

Influenza

Influenza, or flu, is a contagious respiratory infection caused by several flu viruses that infect the nose, throat and lungs. People infected with the seasonal flu virus feel miserable with fever, chills, muscle aches, coughing, congestion, headache and fatigue for a week or so. Most people who get the flu get better within two weeks, but some people may develop serious complications, such as pneumonia. Pandemic influenza is when a new flu virus strain occurs that can spread easily from person-to-person and the virus is one for which most people have no immunity.

Photograph a Phlebotomus papatasi sand fly.

Leishmaniasis

Leishmaniasis is a parasitic disease transmitted by the bites of infected sand flies. It is found in nearly 88 countries, from rain forests in Central and South America to deserts in the Middle East and west Asia. Some cases of the disease have also appeared in Mexico and Texas. The disease takes several different forms, including the most common cutaneous leishmaniasis, which causes skin sores, and the more severe visceral leishmaniasis (also known as kala azar), which affects internal organs such as the spleen, liver, and bone marrow. 

Micrograph of skin section from leprosy patient.

Leprosy (Hansen's Disease)

Leprosy (Hansen's Disease) is a chronic infectious disease that primarily affects the peripheral nerves, skin, upper respiratory tract, eyes, and nasal mucosa (lining of the nose). The disease is caused by a bacillus (rod-shaped) bacterium known as Mycobacterium leprae.

Lyme Disease Bacteria, Borrelia burgdorferi

Lyme Disease

Lyme disease, or borreliosis, is caused by the bacterium Borrelia burgdorferi and is transmitted to humans through the bite of an infected blacklegged deer tick. It is the most common tickborne infectious disease in the United States.  

Image of malaria-infected red blood cell.

Malaria

Malaria is a mosquito-borne disease that can cause infected people to become very sick with high fever, chills, and flu-like illness. It can also cause death. Substantial progress has been made globally to control and eliminate malaria, but it continues to be a significant public health problem with roughly 3.2 billion people worldwide at risk for the disease.

MERS Coronavirus Particle

MERS & SARS

Middle East Respiratory Syndrome (MERS-CoV) is a viral respiratory illness that was first reported in Saudi Arabia in 2012 and has since spread to several other countries. Most people infected with MERS-CoV developed severe acute respiratory illness, including fever, cough, and shortness of breath; many of them died. Severe acute respiratory syndrome (SARS-CoV), also a severe viral respiratory illness, was first reported in Asia in February 2003 and spread to dozens of countries before being contained. Since 2004, there have been no known SARS cases.

Electron microscope image of the bacteria Bordetella pertussis.

Pertussis (Whooping Cough)

Pertussis, also known as whooping cough, is a highly contagious respiratory disease. It is caused by the bacterium Bordetella pertussis. Pertussis is known for uncontrollable, violent coughing that often makes it hard to breathe. After fits of many coughs, someone with pertussis often needs to take deep breaths, which result in a “whooping” sound.

Image of Yersinia pestis Bacteria

Plague

Plague, caused by the bacterium Yersinia pestis, is a disease that affects humans and other mammals. People typically get infected after being bitten by a rodent flea that is carrying the bacterium or by handling a plague-infected animal. Although the disease killed millions in Europe during the Middle Ages, antibiotics effectively treat plague today. Without prompt treatment, plague can cause serious illness or death. Human plague infections continue to occur in the western United States, but significantly more cases occur in parts of Africa and Asia.

Photo of NIH Clinical Research Center.

Primary Immune Deficiency Diseases (PIDDs)

Primary immune deficiency diseases (PIDDs) are rare, genetic disorders that impair the immune system. Without a functional immune response, people with PIDDs may be subject to chronic, debilitating infections, such as Epstein-Barr virus (EBV), which can increase the risk of developing cancer. Some PIDDs can be fatal. PIDDs may be diagnosed in infancy, childhood, or adulthood, depending on disease severity.

Four nerve cells in a mouse illustrate how infectious prion protein, in red, moves within cells along neurites—wire-like connections the nerve cells use to communicate with adjacent cells.

Prion Diseases

Prion diseases are a related group of rare, fatal brain diseases that affect animals and humans. Also known as transmissible spongiform encephalopathies (TSE), they include bovine spongiform encephalopathy ("mad cow" disease) in cattle; Creutzfeldt-Jakob disease in humans; scrapie in sheep; and chronic wasting disease in deer and elk.

Respiratory Syncytial Virus (RSV)

Respiratory Syncytial Virus (RSV)

Respiratory syncytial virus, or RSV, is a respiratory virus that infects the lungs and breathing passages. Healthy people typically experience mild, cold-like symptoms and recover in a week or two. However, RSV can be serious, particularly for infants and the elderly. RSV is the most common cause of bronchiolitis (inflammation of the small airways in the lung) and pneumonia in children younger than 1 year of age in the United States.