Sexually transmitted infections (STIs) are caused by pathogens transmitted from person to person through sexual contact. STIs can be caused by bacteria, viruses, or parasites. STIs have a devastating impact on adults and infants and affect millions of people in the United States annually. Infection with certain STIs can increase a person’s risk of developing cancer and can increase the likelihood of acquiring or transmitting HIV. In addition, STIs can cause long-term health complications, especially in the reproductive and central nervous systems. In rare cases, STIs can lead to serious illness or death. Research is urgently needed to help reduce the public health burden of STIs.

Respiratory syncytial virus (RSV) infects the lungs and breathing passages, and, in the United States, nearly all children have been infected with RSV by age two. In healthy people, symptoms of RSV infection are usually mild and resolve within a week. However, RSV can cause serious illness or death in vulnerable individuals, including premature and very young infants, children with chronic lung disease or congenital heart disease, and people who are over age 65. In the U.S., RSV is the most common cause of bronchiolitis (inflammation of the small airways in the lungs) in children younger than one year old and causes approximately 58,000 hospitalizations among children under five annually. RSV infection is estimated to cause about 14,000 annual deaths in U.S. adults over age 65. Globally, RSV affects an estimated 64 million people and causes 160,000 deaths each year.

NIAID conducts and supports basic research on RSV to improve understanding of the virus and how it causes disease, as well as factors in animals and humans that affect susceptibility to RSV infection. Research is also underway to develop vaccines to prevent RSV.

Prion diseases are transmissible, untreatable, and fatal brain diseases of mammals. Their cause is highly unusual: The host’s normal prion protein can, for unknown reasons, malfunction and assemble into structured aggregates called prions that cause infectious brain disease. This process – which can be underway for years before symptoms appear – likely causes the most common form of prion disease in people, sporadic Creutzfeldt-Jakob disease (CJD). Other forms of human prion diseases include variant CJD, fatal familial insomnia, Gerstmann-Straussler-Scheinker Syndrome and Kuru.

In livestock and wildlife, prion diseases such as scrapie (sheep), chronic wasting disease (deer, elk, moose), and mad cow disease (cattle) can spread by casual contact or contamination of feeds or the environment. Prions also can be infectious if inadvertently transferred from person to person by invasive medical procedures.

Prion disease symptoms reflect the brain being destroyed and can range from memory loss and unstable movement to being unable to sleep or realize the need to eat.

NIAID scientists have focused research on prion structures, biochemistry, cell biology, pathogenesis, diagnostics, and therapeutics. NIAID also is exploring similarities between prion diseases and other protein misfolding diseases, such as Alzheimer’s and Parkinson’s diseases, Lewy body dementia, and chronic traumatic encephalopathy.

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.

Why Is the Study of Plague a Priority for NIAID?

Plague is a category A pathogen which are those organisms/biological agents that pose the highest risk to national security and public health because they can be easily disseminated or transmitted from person to person, result in high mortality rates and have the potential for major public health impact, might cause public panic and social disruption, and require special action for public health preparedness.

How Is NIAID Addressing This Critical Topic?

NIAID conducts and supports research on the diagnosis, prevention, and treatment of infections caused by microbes, including those that have the potential for use as biological weapons. The research program to address biodefense includes both short- and long-term studies targeted at designing, developing, evaluating, and approving specific tools (diagnostics, drugs, and vaccines) needed to defend against possible bioterrorist-caused disease outbreaks.

Gonorrhea is a sexually transmitted infection (STI) caused by the bacteria Neisseria gonorrhoeae. N. gonorrhoeae infects the reproductive tract, including the cervix, uterus, and fallopian tubes in women, and the urethra in women and men. N. gonorrhoeae can also establish infection in the mouth, throat, eyes, and rectum. It is becoming more difficult to treat gonorrhea, as strains have been isolated that are resistant to the last antibiotic approved for treatment. NIAID supports a comprehensive, multidisciplinary program of research on N. gonorrhoeae that includes basic research on pathogens, improved diagnostics, preventive vaccines, and additional alternative treatments. 

Schistosomiasis, also known as bilharzia or snail fever, is an acute and chronic disease caused by parasitic flatworms called schistosomes or blood flukes. Most human infections are caused by Schistosoma mansoni, S. haematobium, or S. japonicum. The parasites spend part of their lifecycle in freshwater snails. The infectious, larval form emerges from the snail and contaminates water.

People who contact contaminated water during recreational, agricultural, or domestic activities become infected when the fork-shaped larval worms penetrate their skin, travel to blood vessels, and develop into adults. The release of eggs from female worms triggers symptoms in infected people, which can include abdominal pain, diarrhea, and blood in the urine. In children, repeated infections may cause anemia and stunted growth. Chronic infections frequently result in serious damage to the liver, intestines, and bladder. Women who are exposed to infested water through such routine tasks as clothes washing can develop urogenital schistosomiasis, which may result in tissue damage that increases the risk of HIV transmission.

Why Is the Study of Schistosomiasis (Bilharzia) a Priority for NIAID?

Although the parasites that cause human schistosomiasis are not found in the United States, at least 220 million people are infected worldwide, particularly in rural communities where people routinely collect water from lakes, rivers or small bodies of water for household or agricultural use. Among parasitic diseases, schistosomiasis is second only to malaria in terms of the high disease and economic burden it imposes

How Is NIAID Addressing This Critical Topic?

NIAID-supported investigators study many aspects of schistosomiasis to find new ways to prevent and treat the disease. Research is directed at the various life-stages of parasite itself as well as the freshwater snails that serve as an intermediate host.

Like other so-called neglected tropical diseases (NTDs), schistosomiasis generally impacts the world’s poorest people. Learn about NIAID research efforts on other NTDs.

The NIAID-funded Schistosomiasis Research Center provides investigators with a number of resources to advance their studies, including egg and larval parasites, snails and molecular reagents and other tools needed to conduct research.

This video describes the resources available from the Schistosomiasis Research Center.

VIDEO: Scientists studying schistosomiasis rely on NIAID for an unusual research resource—snails.

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.