Cause

Evidence is overwhelming that Human Immunodeficiency virus (HIV) causes Acquired Immunodeficiency Syndrome (AIDS). HIV infects a number of cell types important to activating and sustaining an effective immune response. Chief among these cells are CD4⁺ T-helper cells. HIV replication destroys CD4⁺ T-helper cells. Loss of CD4⁺ T-helper cells reduces the body's ability to fight off infection by organisms which are ordinarily kept in check by a healthy immune system.

Scope

The National Institute of Allergy and Infectious Disease states that:

• More than 1 million people in the U.S. currently are living with HIV/AIDS.
• 21 percent of those infected with HIV are unaware of their infection.
• In 2006, there were approximately 53,600 new HIV infections

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Risk Factors

• transfusion of blood products prior to 1986
• unprotected sex with an infected partner
• sharing infected needles or syringes
• mother to child exposure during birth or breastfeeding
• transfusion of blood products after 1986 - very rare
• transplant of infected tissue - very rare
• occupational exposure - very rare

Diagnosis

During the initial phase of HIV infection, viral replication increases dramatically, then declines to a steady state during the chronic asymptomatic phase of HIV illness. Many individuals have only minor symptoms initially. Others develop a flu-like illness within a month or two after exposure to the virus. Early HIV symptoms may be mistaken for another type of viral infection:

• fever
• headache
• fatigue
• enlarged lymph nodes in the neck and groin

HIV infection can be verified by a number of tests.

• Enzyme immunoassay detects HIV antibodies in blood, urine or oral fluid. Rapid tests can return results within 30 minutes.
• RNA tests detect HIV RNA. They are used to detect early HIV infection before sufficient antibodies are produced for immunoassay. These tests are used to screen the blood supply.

A diagnosis of AIDS requires: HIV verification plus CD4⁺ T cell count < 200 cells per cubic millimeter (200/mL) of blood or HIV plus an AIDS defining condition.

Symptoms of opportunistic infections common in people with AIDS may include:

• Fever
• Coughing and shortness of breath
• Difficulty or painful swallowing
• Neurological symptoms
  • headaches
  • neuropathy
  • confusion
  • memory loss
  • vision loss
  • loss of coordination
  • coma

• Severe and persistent diarrhea
• Nausea, abdominal cramps, and vomiting
• Weight loss and extreme fatigue

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AIDS is diagnosed when a person has a CD4⁺ T count of less than or equal to 200/mL or if they develop an AIDS defining illness.