what are HIV and AIDS?

What are HIV and AIDS? 

Electron microscope image of HIV, seen as small spheres on the surface of white blood cells.

HIV is the human immunodeficiencyvirus. It is the virus that can lead toacquired immune deficiencysyndrome, or AIDS. CDC estimates that about 56,000 people in the United States contracted HIV in 2006.

There are two types of HIV, HIV-1 and HIV-2. In the United States, unless otherwise noted, the term “HIV” primarily refers to HIV-1.

Both types of HIV damage a person’s body by destroying specific blood cells, called CD4+ T cells, which are crucial to helping the body fight diseases.

Within a few weeks of being infected with HIV, some people develop flu-like symptoms that last for a week or two, but others have no symptoms at all. People living with HIV may appear and feel healthy for several years. However, even if they feel healthy, HIV is still affecting their bodies. All people with HIV should be seen on a regular basis by a health care provider experienced with treating HIV infection. Many people with HIV, including those who feel healthy, can benefit greatly from current medications used to treat HIV infection. These medications can limit or slow down the destruction of the immune system, improve the health of people living with HIV, and may reduce their ability to transmit HIV. Untreated early HIV infection is also associated with many diseases including cardiovascular disease, kidney disease, liver disease, and cancer.  Support services are also available to many people with HIV. These services can help people cope with their diagnosis, reduce risk behavior, and find needed services.

AIDS is the late stage of HIV infection, when a person’s immune system is severely damaged and has difficulty fighting diseases and certain cancers. Before the development of certain medications, people with HIV could progress to AIDS in just a few years. Currently, people can live much longer - even decades - with HIV before they develop AIDS. This is because of “highly active” combinations of medications that were introduced in the mid 1990s.

No one should become complacent about HIV and AIDS. While current medications can dramatically improve the health of people living with HIV and slow progression from HIV infection to AIDS, existing treatments need to be taken daily for the rest of a person’s life, need to be carefully monitored, and come with costs and potential side effects. At this time, there is no cure for HIV infection. Despite major advances in diagnosing and treating HIV infection, in 2007, 35,962 cases of AIDS were diagnosed and 14,110 deaths among people living with HIV were reported in the United States.

Read our Questions and Answers about HIV and AIDS science.

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Where did HIV come from?

Scientists identified a type of chimpanzee in West Africa as the source of HIV infection in humans. They believe that the chimpanzee version of the immunodeficiency virus (called simian immunodeficiency virus or SIV) most likely was transmitted to humans and mutated into HIV when humans hunted these chimpanzees for meat and came into contact with their infected blood. Over decades, the virus slowly spread across Africa and later into other parts of the world.

For more information, read our Question and Answer about where HIV came from.

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HIV-2

In 1986, a second type of HIV, called HIV-2, was isolated from AIDS patients in West Africa. HIV-2 has the same modes of transmission as HIV-1 and is associated with similar opportunistic infections and AIDS. In persons infected with HIV-2, immunodeficiency seems to develop more slowly and to be milder, and those with HIV-2 are comparatively less infectious early in the course of infection. As the disease advances, HIV-2 infectiousness seems to increase; however, compared with HIV-1, the duration of this increased infectiousness is shorter.

HIV-2 infections are predominantly found in Africa. West African nations with a prevalence of HIV-2 of more than 1% in the general population are Cape Verde, Côte d'Ivoire (Ivory Coast), Gambia, Guinea-Bissau, Mali, Mauritania, Nigeria, and Sierra Leone. Other West African countries reporting HIV-2 are Benin, Burkina Faso, Ghana, Guinea, Liberia, Niger, São Tomé, Senegal, and Togo. Angola and Mozambique are other African nations where the prevalence of HIV-2 is more than 1%.

The first case of HIV-2 infection in the United States was diagnosed in 1987. Since then, the Centers for Disease Control and Prevention (CDC) has worked with state and local health departments to collect demographic, clinical, and laboratory data on persons with HIV-2 infection.