What is HIV?
HIV is a virus that damages the immune system. The immune system helps the body fight off infections. Untreated HIV infects and kills CD4 cells, which are a type of immune cell called T cells. Over time, as HIV kills more CD4 cells, the body is more likely to get various types of infections and cancers.
HIV is transmitted through bodily fluids that include:
vaginal and rectal fluids
The virus doesn’t spread in air or water, or through casual contact.
HIV is a lifelong condition and currently there is no cure, although many scientists are working to find one. However, with medical care, including treatment called antiretroviral therapy, it’s possible to manage HIV and live with the virus for many years.
Without treatment, a person with HIV is likely to develop a serious condition called AIDS. At that point, the immune system is too weak to fight off other diseases and infections. Untreated, life expectancy with AIDS is about three yearsTrusted Source. With antiretroviral therapy, HIV can be well-controlled and life expectancy can be nearly the same as someone who has not contracted HIV.
It’s estimated that 1.1 million Americans are currently living with HIV. Of those people, 1 in 5 don’t know they have the virus.
HIV can cause changes throughout the body. Learn about the effects of HIV on the different systems in the body.
AIDS is a disease that can develop in people with HIV. It’s the most advanced stage of HIV. But just because a person has HIV doesn’t mean they’ll develop AIDS.
HIV kills CD4 cells. Healthy adults generally have a CD4 count of 500 to 1,500 per cubic millimeter. A person with HIV whose CD4 count falls below 200 per cubic millimeter will be diagnosed with AIDS.
A person can also be diagnosed with AIDS if they have HIV and develop an opportunistic infection or cancer that’s rare in people who don’t have HIV. An opportunistic infection, such as pneumonia, is one that takes advantage of a unique situation, such as HIV.
Untreated, HIV can progress to AIDS within a decade. There’s no cure for AIDS, and without treatment, life expectancy after diagnosis is about three yearsTrusted Source. This may be shorter if the person develops a severe opportunistic illness. However, treatment with antiretroviral drugs can prevent AIDS from developing.
If AIDS does develop, it means that the immune system is severely compromised. It’s weakened to the point where it can no longer fight off most diseases and infections. That makes the person vulnerable to a wide range of illnesses, including:
oral thrush, a fungal infection in the mouth or throat
cytomegalovirus (CMV), a type of herpes virus
cryptococcal meningitis, a fungal infection in the brain
toxoplasmosis, a brain infection caused by a parasite
cryptosporidiosis, an infection caused by an intestinal parasite
The shortened life expectancy linked with untreated AIDS isn’t a direct result of the syndrome itself. Rather, it’s a result of the diseases and complications that arise from having an immune system weakened by AIDS. Learn more about possible complications that can arise from HIV and AIDS.
To develop AIDS, a person has to have contracted HIV. But having HIV doesn’t necessarily mean that someone will develop AIDS.
Cases of HIV progress through three stages:
stage 1: acute stage, the first few weeks after transmission
stage 2: clinical latency, or chronic stage
stage 3: AIDS
As HIV lowers the CD4 cell count, the immune system weakens. A typical adult’s CD4 count is 500 to 1,500 per cubic millimeter. A person with a count below 200 is considered to have AIDS.
How quickly a case of HIV progresses through the chronic stage varies significantly from person to person. Without treatment, it can last up to a decade before advancing to AIDS. With treatment, it can last indefinitely.
There is no cure for HIV, but it can be controlled. People with HIV often have a near-normal lifespan with early treatment with antiretroviral therapy. Along those same lines, there’s technically no cure for AIDS. However, treatment can increase a person’s CD4 count to the point where they’re considered to no longer have AIDS. (This point is a count of 200 or higher.) Also, treatment can typically help manage opportunistic infections.
HIV and AIDS are related, but they’re not the same thing. Learn more about the difference between HIV and AIDS.
Anyone can contract HIV. The virus is transmitted in bodily fluids that include:
vaginal and rectal fluids
Some of the ways HIV is spread from person to person include:
through vaginal or anal sex — the most common route of transmission, especially among men who have sex with men
by sharing needles, syringes, and other items for injection drug use
by sharing tattoo equipment without sterilizing it between uses
during pregnancy, labor, or delivery from a woman to her baby
through “pre-mastication,” or chewing a baby’s food before feeding it to them
through exposure to the blood of someone living with HIV, such as through a needle stick
The virus can also be transmitted through a blood transfusion or organ and tissue transplant. However, rigorous testing for HIV among blood, organ, and tissue donors ensures that this is very rare in the United States.
It’s theoretically possible, but considered extremely rare, for HIV to spread through:
oral sex (only if there are bleeding gums or open sores in the person’s mouth)
being bitten by a person with HIV (only if the saliva is bloody or there are open sores in the person’s mouth)
contact between broken skin, wounds, or mucous membranes and the blood of someone living with HIV
HIV does NOT spread through:
hugging, shaking hands, or kissing
air or water
sharing food or drinks, including drinking fountains
saliva, tears, or sweat (unless mixed with the blood of a person with HIV)
sharing a toilet, towels, or bedding
mosquitoes or other insects
It’s important to note that if a person with HIV is being treated and has a persistently undetectable viral load, it’s virtually impossible to transmit the virus to another person. Learn more about HIV transmission.
HIV is a variation of a virus that infects African chimpanzees. Scientists suspect the simian immunodeficiency virus (SIV) jumped from chimps to humans when people consumed infected chimpanzee meat. Once inside the human population, the virus mutated into what we now know as HIV. This likely occurred as long ago as the 1920s.
HIV spread from person to person throughout Africa over the course of several decades. Eventually, the virus migrated to other parts of the world. Scientists first discovered HIV in a human blood sample in 1959.
It’s thought that HIV has existed in the United States since the 1970s, but it didn’t start to hit public consciousness until the 1980s. Learn more about the history of HIV and AIDS in the United States.
AIDS is caused by HIV. A person can’t get AIDS if they haven’t contracted HIV.
Healthy individuals have a CD4 count of 500 to 1,500 per cubic millimeter. Without treatment, HIV continues to multiply and destroy CD4 cells. If a person’s CD4 count falls below 200, they have AIDS.
Also, if someone with HIV develops an opportunistic infection associated with HIV, they can still be diagnosed with AIDS, even if their CD4 count is above 200.
Several different tests can be used to diagnose HIV. Healthcare providers determine which test is best for each person.
Antibody/antigen tests are the most commonly used tests. They can show positive results typically within 18–45 daysTrusted Source after someone initially contracts HIV.
These tests check the blood for antibodies and antigens. An antibody is a type of protein the body makes to fight an infection. An antigen, on the other hand, is the part of the virus that activates the immune system.