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Picture of an AIDS awareness ribbon

What is AIDS?

AIDS (acquired immune deficiency syndrome) is caused by the human immunodeficiency virus (HIV), which kills or impairs cells of the immune system and progressively destroys the body's ability to fight infections and certain cancers. HIV is most commonly spread by sexual contact with an infected partner.

The term AIDS applies to the most advanced stages of an HIV infection. Official criteria for the definition of AIDS are developed by the Centers for Disease Control and Prevention (CDC), which is responsible for tracking the spread of AIDS in the United States. The 2008 CDC definition of AIDS includes all HIV-infected people who have fewer than 200 CD4+ T cells (healthy adults usually have CD4+ T-cell counts of 800 or more.) In addition, the definition includes HIV-infected people who have been diagnosed with one or more of 26 clinical conditions (opportunistic infections) that affect people with advanced HIV disease.

According to the CDC, at the end of 2006, an estimated 1.1 million adults and adolescents were living with HIV/AIDS in the United States. An estimated 2.7 million new HIV infections occurred worldwide during 2007, which equates to about five new infections every minute. This indicates that the AIDS epidemic still rages out of control. According to the World Health Organization (WHO), at the end of 2008, there were 33.4 million people living with AIDS globally.

How is HIV/AIDS transmitted?

Sexual contact

HIV is spread most commonly by sexual contact with an infected partner. The virus enters the body through the lining of the vagina, vulva, penis, rectum, or mouth during sexual activity.

Blood contamination

HIV may also be spread through contact with infected blood. However, due to the screening of blood for evidence of HIV infection, the risk of acquiring HIV from blood transfusions is extremely low.


HIV is frequently spread by sharing needles, syringes, or drug use equipment with someone who is infected with the virus. Transmission from patient to healthcare worker, or vice-versa through accidental sticks with contaminated needles or other medical instruments, is rare.


HIV also can be spread to babies born to, or breastfed by, mothers infected with the virus.

HIV/AIDS cannot be spread through:

  • Saliva

  • Sweat

  • Tears

  • Casual contact, such as sharing food utensils, towels, and bedding

  • Swimming pools

  • Telephones

  • Toilet seats

  • Biting insects (such as mosquitoes)

What are the symptoms of HIV/AIDS?

Some people may develop a flu-like illness within a month or two after exposure to the HIV virus, although, many people do not develop any symptoms at all when they first become infected. In addition, the symptoms that do appear, which usually disappear within a week to a month, are often mistaken for those of another viral infection. These may include:

  • Fever

  • Headache

  • Malaise

  • Enlarged lymph nodes

Persistent or severe symptoms may not surface for 10 years or more, after HIV first enters the body in adults, or within two years in children born with an HIV infection. This "asymptomatic" period of the infection is highly variable from person to person. But, during the asymptomatic period, HIV is actively infecting and killing cells of the immune system. Its most obvious effect is a decline in the blood levels of CD4+ T cells (also called T4 cells)--the immune system's key infection fighters. The virus initially disables or destroys these cells without causing symptoms.

As the immune system deteriorates, complications begin to surface. The following are the most common complications, or symptoms, of AIDS. However, each individual may experience symptoms differently. Symptoms may include:

  • Lymph nodes that remain enlarged for more than three months

  • Lack of energy

  • Weight loss

  • Frequent fevers and sweats

  • Persistent or frequent yeast infections (oral or vaginal)

  • Persistent skin rashes or flaky skin

  • Pelvic inflammatory disease that does not respond to treatment

  • Short-term memory loss

  • One or more infections (opportunistic infections) related to having a diminished immune system, such as tuberculosis and certain types of pneumonia 

Some people develop frequent and severe herpes infections that cause mouth, genital, or anal sores, or a painful nerve disease known as shingles. Children may have delayed development or failure to thrive.

During the course of the HIV infection, most people experience a gradual decline in the number of CD4+ T cells, although some individuals may have abrupt and dramatic drops in their counts.

The symptoms of an HIV infection may resemble other medical conditions. Always consult your doctor for a diagnosis.

How is HIV/AIDS diagnosed?

Early HIV infection often causes no symptoms, and must be detected by testing a person's blood for the presence of antibodies--disease-fighting proteins--against HIV. These HIV antibodies generally do not reach levels high enough to detect by standard blood tests until one to three months following infection, and may take as long as six months. People exposed to HIV should be tested for HIV infection as soon as they are likely to develop antibodies to the virus.

When a person is highly likely to be infected with HIV and yet antibody tests are negative, a test for the presence of HIV itself in the blood is used. Repeat antibody testing at a later date, when antibodies to HIV are more likely to have developed, is often recommended.

Treatment for HIV/AIDS

As with many other conditions, early detection offers more options for treatment. Today, there are medical treatments that can slow down the rate at which HIV weakens the immune system, but currently there is no cure for the disease. However, there are other treatments that can prevent or cure the conditions associated with AIDS. Consult your doctor for more information regarding various drug therapies for the treatment of HIV/AIDS.

Are we getting close to finding a vaccine for AIDS?

Yes, however, even with extensive prevention efforts from multiple government and private agencies, HIV is still spreading worldwide.

In an attempt to develop a vaccine against HIV, which could protect against infection and disease, an AIDS vaccine, called AIDSvax, was tested in several countries, including the US. The vaccine composition tested varies from country to country, because different strains of HIV are found in Asia than in North America, for example. Designed to stimulate the body to produce antibodies to certain types of HIV, results from the first large-scale clinical trials of an AIDS vaccine show the inoculation is largely ineffective in protecting people from the AIDS-causing HIV virus.

But the research does offer some hope. The shot did appear to significantly lower the infection rate among African-Americans and other non-Hispanic minorities, according to the company that produces the AIDSvax vaccine.

Researchers say they are at a loss to explain the apparent differences in responses among racial and ethnic groups. Always consult your doctor for more information.