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HIV (Human Immunodeficiency Virus) Infection - What Happens

How HIV is spread

HIV is spread when blood, semen, or vaginal fluids from an infected person enter another person's body, usually through:

  • Sexual contact. The virus may enter the body through a tear in the lining of the rectum, vagina, urethra, or mouth. Most cases of HIV are spread this way.
  • Infected blood. HIV can be spread when a person:
    • Shares needles, syringes, cookers, cotton, cocaine spoons, or eyedroppers used for injecting drugs or steroids.
    • Is accidentally stuck with a needle or other sharp item that is contaminated with HIV.

HIV may be spread more easily in the early stage of infection and again later, when symptoms of HIV-related illness develop.

Recommended Related to HIV/AIDS

Understanding AIDS/HIV -- Prevention

The most common way people are infected with HIV is by having sex with an infected person. You can't tell by looking at a person whether they have HIV, so you have to protect yourself -- and your sex partner. Safe Sex and HIV Prevention Don't have unprotected sex outside marriage or a committed relationship. If you or your partner has ever had unprotected sex -- or if either of you uses injected drugs -- the only way to be sure you don't have HIV is to get tested. Have two...

Read the Understanding AIDS/HIV -- Prevention article > >

A woman who is infected with HIV can spread the virus to her baby during pregnancy, delivery, or breast-feeding.

How HIV is not spread

The virus doesn't survive well outside the body. So HIV cannot be spread through casual contact with an infected person, such as by sharing drinking glasses, by casual kissing, or by coming into contact with the person's sweat or urine.

It is now extremely rare in the United States for HIV to be transmitted by blood transfusions or organ transplants.

The window period

After you've been infected, it can take 2 weeks to 6 months for your body to start making HIV antibodies.

This means that during this time you could have a negative HIV test, even though you have been infected and can spread the virus to others.

This is commonly called the "window period," or seroconversion period.

Stages of HIV

Most people go through the following stages after being infected with HIV:

Initial stage (stage 1)

The first stage of HIV infection is defined by the U.S. Centers for Disease Control and Prevention (CDC) as a CD4+ cell count of at least 500 cells per microliter or a percentage of CD4+ cells at least 29% of all lymphocytes. People in this stage don't have any symptoms.3

Chronic stage (stage 2)

The second stage of HIV infection is defined by the CDC as a CD4+ cell count of 200 to 499 or a percentage of CD4+ cells of 14% to 28%.3 It may take years for HIV symptoms to develop during this stage. But even though no symptoms are present, the virus is making copies of itself (multiplying) in the body during this time.

HIV multiplies so quickly that the immune system can't destroy the virus. After years of fighting HIV, the immune system starts to weaken.

AIDS (stage 3)

AIDS occurs when the CD4+ cell counts drop below 200, the percentage of CD4+ cells is less than 14%, or an AIDS-defining condition is present.4

If HIV isn't treated, most people get AIDS within 10 to 12 years after the initial infection. With treatment for HIV, the progression to AIDS may be delayed or prevented.


WebMD Medical Reference from Healthwise

Last Updated: May 16, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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