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. Hepatitis C is a blood-borne virus that is largely spread by sharing needles or other drug injection equipment. Hepatitis D, which is transmitted through contact with infectious blood, occurs only among people with hepatitis B infection.

Hepatitis B, C, and D afflict more than half a billion people worldwide and are responsible for more than a million deaths a year. Chronic infection with these viruses can lead to cirrhosis of the liver, end-stage liver disease, and liver cancer.

Hepatitis Research

NIAID supports and conducts research on each of the five known hepatitis viruses—A, B, C, D, and E. During the past 60 years, NIAID-supported investigators have been involved in many important advances in hepatitis research, including:

• Discovery of the hepatitis A and E viruses
• Development of one of the first diagnostic tests for hepatitis A
• Studies that led to the creation of the hepatitis A vaccine
• Studies that laid the foundation for advanced development of a hepatitis E vaccine.

NIAID’s research program emphasizes the study of hepatitis B and C viruses due to the large magnitude of medical burdens that they impose. Studies focus on understanding the immune response to infection, the course of disease development, and developing new therapeutics and vaccines for these viruses.

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.

Why Is the Study of Group A Streptococcal Infections a Priority for NIAID?

Health experts estimate that more than 10 million mild infections (throat and skin) occur every year.

How Is NIAID Addressing This Critical Topic?

NIAID supports research to develop a group A streptococcus vaccine, and several candidate vaccines are in various phases of development. While some scientists are conducting animal model studies to obtain data to pursue clinical trials in humans, other scientists are close to evaluating group A streptococcus vaccine candidates in Phase I clinical trials.

As a result of NIAID-supported research, the first group A streptococcus vaccine clinical trial in 30 years was started. The vaccine was well tolerated by patients and has led to further clinical evaluation of a similar vaccine candidate.

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 lesions, and the more severe visceral leishmaniasis (also known as kala azar), which affects internal organs such as the spleen, liver, and bone marrow. 

Why Is the Study of Leishmaniasis a Priority for NIAID?

The World Health Organization estimates there are between 600,000 and 1 million new cases of cutaneous leishmaniasis and 50,000-70,000 new cases of visceral leishmaniasis in the world each year. Leishmaniasis not only affects people who live in countries where the disease is endemic but also poses a risk to people who travel in those areas. According to the World Health Organization (WHO), 90 percent of all cutaneous leishmaniasis cases occur in Afghanistan, Brazil, Iran, Peru, Saudi Arabia, and Syria.

How Is NIAID Addressing This Critical Topic?

NIAID conducts and supports leishmaniasis research to advance the understanding of all aspects of the disease, including the different species of disease-causing Leishmania parasites, the varieties and biology of sand flies that transmit the parasites to animals and humans, and how the host immune system responds to the infection.  NIAID also supports development of therapeutics for treatment.

Eczema, or atopic dermatitis, is the most common chronic inflammatory skin disease. The condition occurs in 10 to 30 percent of children and 2 to 10 percent of adults in the United States. People with eczema have dry, itchy skin that can weep clear fluid when scratched. The disease also can make people more susceptible to bacterial, viral, and fungal skin infections. Eczema is the strongest risk factor for the development of food allergy. Severe forms of eczema can substantially affect quality of life. The causes of the condition remain unclear.

NIAID conducts and supports basic research in allergy and immunology that increases our understanding of how the immune system and the environment each contribute to the development of eczema and its complications. NIAID also funds person-centered research to explore the genetic determinants of eczema and evaluate new strategies to prevent and treat the disease.

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). These problems can increase the risk of infection and hemorrhage.

Why Is the Study of Autoimmune Lymphoproliferative Syndrome (ALPS) a Priority for NIAID?

ALPS can cause debilitating symptoms and put those affected at an increased risk for developing serious health conditions, including autoimmune diseases and lymphoma. Researchers at NIAID are working to develop safe and effective treatments targeting the genetic defects in people with ALPS and related disorders.

How Is NIAID Addressing This Critical Topic?

Researchers at NIAID focus on gaining a better understanding of the clinical and genetic characteristics of people with ALPS and related disorders. By identifying the genes responsible for ALPS symptoms, NIAID researchers not only help affected families but also increase understanding of how the immune system works.

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.

There are more than 200 different forms of primary immune deficiency diseases (PIDDs) affecting approximately 500,000 people in the United States. These rare genetic diseases may be chronic, debilitating, and costly. Read more about some of the individual PIDDs that NIAID is currently studying.

Since the 1970s, NIAID-supported investigators have been examining the causes and complications of PIDDs to improve the lives of patients and families. NIAID aims to improve diagnosis, explore new treatments and preventions for PIDDs, and facilitate genetic counseling. NIAID is home to the Primary Immune Deficiency Clinic, which provides diagnoses and disease management recommendations to patients and families whose lives are touched by PIDDs.

An estimated 8% of the U.S. population has an autoimmune disease. In this family of disorders, the immune system mistakenly attacks healthy, working parts of the body, damaging them as a result. Researchers believe there are between 80 and 150 autoimmune diseases. Many of them are chronic and often debilitating, with no known cures. Treatments exist for just some of these diseases and don’t work for everyone. 

The immune system is designed to respond to pathogens and other threats like cancer with a built-in safeguard to avoid autoimmunity. Even so, the immune system can malfunction in ways that lead to autoimmune disease. NIAID-supported research seeks to understand how the immune system contributes to autoimmunity, to develop better diagnostic tools and animal models of autoimmune disease, and to identify effective treatment and prevention strategies. Unlike disease-specific research, this research approach has the potential to improve understanding and lead to treatments for many different autoimmune diseases.

NIAID-supported research has led to the identification of specific immune cells and molecular pathways involved in autoimmune disease, and consequently, to new treatment targets. This has contributed to an explosion in the number of therapies available, yet more work remains. Gaps persist in healthcare providers’ ability to match each person with the right therapy, in the availability of immune therapies that don’t increase the risk of infection, and in the existence of strategies to prevent and cure autoimmune diseases.

West Nile virus (WNV) is a member of the flavivirus family, which includes other mosquito-borne viruses such as dengue and Zika. WNV emerged for the first time in the Western Hemisphere in New York City in 1999 and has since spread across the United States. It is now the most common arthropod-borne virus found in the U.S. 

Most people (about 8 out of 10) who are infected with WNV develop no symptoms at all, while a smaller proportion develop mild symptoms of fever, body aches, skin rash, and swollen lymph nodes. If the virus crosses the blood-brain barrier, however, it can cause life-threatening conditions that include inflammation of the brain and spinal cord. There are no specific therapies for serious WNV infection and there is currently no vaccine available to prevent infection. 

NIAID supports research aimed at better understanding of the interactions between WNV virus, mosquitoes, and the human immune response, as well as broad-spectrum anti-flavivirus drug discovery efforts. 

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

Why Is the Study of Asthma a Priority for NIAID?

Asthma reduces quality of life and is a major contributing factor to missed time from school and work. Severe asthma attacks may require emergency room visits and hospitalizations, and they can be fatal. Existing asthma treatments focus on preventing or controlling disease symptoms. While treatment based on NIH guidelines is generally effective at improving asthma control, many people still experience symptoms on a regular basis and suffer from asthma attacks, which can be frightening and dangerous. NIAID and other NIH institutes studying asthma are committed to reducing the burden of this disease, which disproportionately affects minorities and families living at or below the poverty line.

How Is NIAID Addressing This Critical Topic?

NIAID supports targeted research to understand the underlying immune responses that lead to asthma. This understanding may aid the development of asthma prevention strategies and treatments to improve life for those already living with the disease. NIAID research focuses on understanding how environmental exposures interact with a person’s genetic makeup to cause immune responses that contribute to development of asthma or increase its severity.

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.  

State health departments reported 42,743 confirmed or probable cases to the Centers for Disease Control and Prevention (CDC) in 2017. Reported cases are not believed to reflect the actual incidence of Lyme disease, and CDC estimates that 300,000 cases likely occur annually. The incidence of Lyme disease, as with many other tick-borne diseases, has increased dramatically over the past 10 years.