Synonyms: Human immunodeficiency virus

Medical Specialties: Internal medicine

Clinical Definition

HIV, or human immunodeficiency virus, is a retrovirus that destroys the vital CD4 + T-cells of the immune system. Destruction of CD4 cells decreases immune system function and leaves patients susceptible to infections and disease. The infection can progress into acquired immunodeficiency syndrome (AIDS) if CD4+ T cells decrease to less than 200 cells per cubic millimeter of blood, or if an opportunistic infection like pneumocystis pneumonia is present.  

In Our Own Words

Although HIV and AIDS may be used interchangeably, they are not the same thing. HIV is an infection of the human immunodeficiency virus. The virus is transmitted through contact with bodily fluids, such as vaginal and anal secretions, semen and blood. As a result of long-term infection, acquired immunodeficiency syndrome (AIDS) can develop.

The AIDS virus attacks the white blood cells in the immune system, which help battle disease. As the virus infects the cells, the immune system functions improperly and the body may be unable to fight off invading infections. When the number of white blood cells, referred to as “T cells” decreases to a certain level, or when complication of the HIV virus develop, a doctor will make the diagnosis of AIDS. 

Relevant Conditions
  • Sexually transmitted diseases
  • Depression
  • Intravenous drug use
Common Types
  • HIV-1
Side Effects
  • Chills
  • Night sweats
  • Fever
  • Fatigue
Share this article
  • National Institute of Allergy and Infectious Disease. “What are HIV and AIDS?” Accessed Aug. 2013.
  • U.S. Department of Health and Human Services. Office on Women’s Health: “How is AIDS Different from HIV?” Accessed Aug. 2013.
  • World Health Organization. HIV/AIDS. Accessed Aug. 2013.
  • University of California at San Francisco. CSF Medical Center, AIDS. Accessed Aug. 2013.
Keep Reading

Investigate your bodys signs and signals.
Try Symptom Checker