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.

HIV attacks the immune system by destroying CD4+ T cells, a type of white blood cell that is vital to fighting off infection. The destruction of these cells can leave people with untreated HIV vulnerable to life-threatening infections and complications. Today, effective anti-HIV medications allow people with HIV to lead long, healthy lives. When taken as prescribed, these daily medications, called antiretroviral therapy (ART), can suppress the amount of virus in the blood to a level so low that it is undetectable by standard tests. People with HIV who maintain a durably undetectable viral load by taking daily ART cannot sexually transmit the virus, a concept known as Undetectable=Untransmittable, or U=U. For those who are HIV-negative, numerous methods of preventing HIV acquisition are available, including pre-exposure prophylaxis ( PrEP), post-exposure prophylaxis (PEP), and voluntary adult medical male circumcision.

Why Is the Study of HIV/AIDS a Priority for NIAID?

HIV remains a major global public health concern. HIV treatment and prevention begin with knowing one’s HIV status. Effective treatments are available to help people with HIV live long, healthy lives and prevent HIV transmission to others. Additional prevention tools are available for those who are HIV-negative. In addition to existing treatment and prevention methods, a safe and effective vaccine is needed to ensure a durable end to the HIV pandemic. As the leading U.S. government institute for biomedical HIV/AIDS research, NIAID is committed to conducting research to prevent new transmissions, end HIV-related deaths and complications, and discover a cure.

How Is NIAID Addressing This Critical Topic?

NIAID researchers and grantee institutions advance understanding of disease mechanisms and cooperate to move novel HIV prevention and treatment strategies from basic research into clinical practice. With the generous help of clinical research volunteers, investigators at NIH and around the world create opportunities for the discovery, development and evaluation of technologies and tools that can play a role in decreasing HIV transmission, improving the health of people with HIV, and ultimately ending the pandemic.

Clinical Trials

NIAID and the National Institutes of Health (NIH) conduct ongoing clinical research on HIV infection and other immunological disorders. Read more about the active clinical trials below:

HIV Testing Sites & Care Services Locator

Related Public Health and Government Information

To learn about HIV/AIDS risk factors, screening, and more information on how to prevent and treat HIV, visit the Centers for Diseases Control and Prevention (CDC) HIV/AIDS site.


Response to the virus that causes COVID-19 is an evolving situation in which scientists are learning more each day. There is no evidence so far to determine whether people living with HIV are at a greater risk of acquiring the virus that causes COVID-19 or experiencing severe disease. NIAID will update this section as more information becomes available. At this time, please refer to Interim guidance for COVID-19 and persons with HIV from the HHS HIV/AIDS Guidelines Panels and COVID-19 and People with HIV from

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