What is HIV/AIDS?
The term AIDS (Acquired Immune Deficiency Syndrome) refers to the
most advanced stages of an infection caused by the human immunodeficiency virus
(HIV). The current definition of AIDS includes:
- All HIV-infected people who have fewer than 200 CD4+ T cells
(also called T4 cells). These cells are key infection fighters in the body’s
immune system. Healthy adults often have CD4+ T-cell counts of around 600 or
- HIV-infected people who have been diagnosed with 1 or more
health conditions that affect people with advanced HIV disease. These conditions
include certain cancers. They also include infections that occur because of
HIV’s effect on the immune system (called opportunistic infections).
According to the CDC, about 1.5 million adults and teens are
living with HIV infection in the U.S. Many more people are living with HIV infection
outside the U.S., particularly in sub-Saharan Africa. The HIV epidemic is still not
well-controlled in some parts of the world.
What causes HIV/AIDS?
AIDS is caused by the human immunodeficiency virus (HIV). HIV
destroys or hurts immune system cells. It weakens the body’s ability to fight
infections and certain cancers. HIV is most often spread by having sex with an
infected partner whose HIV is not diagnosed or not under control. Another way to
spread HIV is by having contact with infected blood from contaminated needles,
syringes, or other drug equipment.
HIV can’t be cured. But it can be controlled. And much of the
damage from the infection can be reversed or prevented. But if HIV is left
untreated, serious infections and cancers occur because of the weakened immune
system. And the virus can be passed on to others.
Who is at risk for HIV/AIDS?
The risk of becoming infected with HIV depends on the type of
activity. HIV is spread through blood, pre-seminal fluid and semen, fluids from the
vagina and rectum, and breastmilk. So these types of behaviors put people at risk of
getting or becoming infected with HIV:
- Having vaginal or anal sex with a person infected with HIV
whose virus is not under control. Sexual contact is the most common way the
virus is spread. The virus enters the body through the lining of the vagina,
penis, rectum, or mouth during sexual activity. Unprotected anal sex has the
highest risk of transmission.
- Having multiple sex partners. This includes any partners
whose HIV status is not known. It also includes a partner who has HIV, but whose
virus is not under control. Or a partner who has poor or uncertain control of
- Having high-risk sexual partners. This includes a partner
who is a sex worker, or someone who has sex with many other people. Or someone
who uses IV drugs.
- Sharing needles, syringes, or other drug equipment with
someone with HIV whose virus is not under control.
Other factors that can put people at risk include:
Using alcohol and other
drugs. These can harm someone’s judgment. They make it more likely that
people will do risky things such as having unprotected sex.
Having a sexually transmitted
disease (STD). STDs can cause changes in the tissue of the vagina or
penis. They can make it easier for HIV to pass while you’re having sex
Having an accidental stick
from a needle or medical device contaminated with HIV. But it is rare
for a person with HIV to spread the virus to a healthcare worker this way. Or
for a healthcare worker to spread the virus to a patient.
Having a blood
transfusion. HIV may also be spread through contact with infected blood.
But the risk of getting HIV from blood transfusions is very low. This is because
blood is screened for signs of HIV infection in the U.S.
Having sex without knowing
your partner’s HIV status.
Risks to an unborn child. A
mother infected with HIV can give her baby the virus before or during birth. This is
especially true if her HIV is not well controlled. She can also pass the virus by
breastfeeding. Pregnant women should always be tested and treated for HIV.
Being exposed to these things does not put you at risk for getting
- Casual contact, such as sharing food utensils, towels, and
- Swimming pools
- Toilet seats
- Biting insects (such as mosquitos)
What are the symptoms of HIV/AIDS?
Many people develop a flu-like illness within 2 to 6 weeks after
exposure to the HIV virus. But about 5 out of 10 people don’t have any symptoms at
all when they first become infected. In addition, the symptoms that do appear often
go away within a week to a month. And they are often mistaken for those of another
viral infection. These symptoms may include:
- General feeling of discomfort (malaise)
- Enlarged lymph nodes
Constant or severe symptoms may not show up for 10 years or more
after HIV first enters the body in adults. In children born with an HIV infection,
it may take 2 years for symptoms to appear. This period of no symptoms can be
different for each person. But during this time, HIV is actively infecting and
killing immune system cells. Its most clear effect is a decrease in the number of
CD4+ T cells. These cells are key infection fighters in the immune system.
As the immune system weakens, complications or symptoms begin to
appear. Symptoms of advanced HIV disease and AIDS may be different for each person.
Symptoms may include:
- Lymph nodes that stay enlarged for more than 3 months
- Lack of energy
- Weight loss
- Frequent fevers and sweats
- Constant or frequent yeast infections (oral or vaginal)
- Constant skin rashes or flaky skin
- Diarrhea that keeps coming back
- Short-term memory loss
- One or more infections (opportunistic infections) linked to
having a weakened immune system. These include tuberculosis and certain types of
Some people develop frequent and severe herpes infections. These
cause mouth, genital, or anal sores, or a painful nerve disease known as shingles.
Children may have delayed development or slowed growth (failure to thrive).
During the course of the HIV infection, most people have a slow
decline in the number of CD4+ T cells. Some people may have sudden and severe drops
in these cell counts.
The symptoms of HIV infection may look like other health
conditions. Always talk with your healthcare provider for a diagnosis. Quick
diagnostic tests are available and early diagnosis is important.
How is HIV/AIDS diagnosed?
There are several types of HIV tests used to diagnose HIV
infection. Early HIV infection often causes no symptoms. It must be found by testing
a person’s blood for disease-fighting proteins (antibodies) against HIV. Or the
virus itself can be detected. Tests used to find antigen-antibody are a preferred
method of testing. Antigens are foreign substances (virus). They cause a response
from the body’s immune system. Antibodies are made by the body to fight the
antigens. Testing for antibodies and the virus may not be positive until 2 to 12
weeks after infection. People exposed to HIV should be tested for HIV infection as
soon as they think they may have been exposed to the virus. In some cases a person
may have been recently exposed or possibly exposed to HIV and early testing is
negative. Then repeat testing in 2 to 12 weeks will often be advised.