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Human Immunodeficiency Virus (HIV)

Quick Facts

What is it?

  • Human immunodeficiency virus (HIV) is a sexually transmitted disease (STD) that damages white blood cells that are very important in helping the body fight infection and disease.
  • The most reliable way to avoid transmission of STDs is to abstain from oral, vaginal, and anal sex or to be in a long-term, mutually monogamous relationship with a partner known to be uninfected.
Testing available, including fluid, blood, and other tests.No cure, but medication is available to help manage the disease.Abstain from vaginal, oral, and anal sex. Avoid sharing needles & syringes.

What is HIV?

HIV stands for the human immunodeficiency virus. HIV damages white blood cells (CD4+ or T cells) that are very important and help the body fight infection and disease. As the disease progresses, people have fewer of these cells in their blood and the immune system becomes weak and damaged. When this happens, HIV can lead to AIDS, or acquired immunodeficiency syndrome.

How common is HIV?

It is estimated that there are over 56,000 new cases of HIV in the United States each year. That is equal to someone being infected with HIV every 9½ minutes.

About 20 in 100 infected Americans do not know they have the virus. The fact that so many people are unaware that they have HIV is important because even if you do not have HIV symptoms, you can still infect your sex partners.

HIV affects people from all backgrounds. Anyone who has sex can be at risk regardless of age, race, gender, or sexual orientation, although some groups are at higher risk:

  • Nearly half of all new HIV infections occur in African-Americans.
  • Gay and bisexual men account for more than half of all new HIV cases. For information on HIV's impact on this population, visit cdc.gov.

How is HIV spread?

HIV is transmitted through body fluids such as blood, semen (cum), pre-seminal fluid (pre-cum), vaginal fluids, and breast milk.

Unprotected vaginal and anal sex are the most common ways the virus is transmitted. It is also possible to contract HIV from oral sex (primarily through performing oral sex), although this is less common than with vaginal and anal sex.

Injection drug use is also a risk for HIV if needles, syringes, and other equipment are shared with someone who is infected. Reusing "spoons" and "cookers" (such as bottle caps, spoons, or water used to dissolve or heat drugs) also carries a risk for transmitting HIV and other blood-borne infections.

An HIV-positive pregnant woman can pass HIV to her fetus before or during labor and through breastfeeding. All pregnant women should be tested for HIV. In the United States, HIV-positive pregnant women who are in care and take medication (antiretroviral therapy) and do not breastfeed have a less than 2 percent chance of transmitting HIV to their fetus. Without treatment, the transmission rate is about 25 percent.

Healthcare workers exposed to infected fluids, most often through needle sticks, are also at risk of HIV. Those workers may benefit from taking medication after exposure (post-exposure prophylaxis or PEP). PEP usually consists of two or three antiretroviral drugs that are effective against HIV. PEP works best within 72 hours after exposure. This treatment can also be given to individuals who may be exposed to HIV outside the workplace, usually through sexual assault, condom breakage, or sharing needles with someone who has HIV (non-occupational post-exposure prophylaxis, or nPEP).

Patients receiving blood transfusions or organ and tissue transplants can be at risk for contracting HIV. However, this risk is extremely rare in the United States, given the strict testing done with blood products and all donated organs and tissues.

Having another STD increases the risk of contracting HIV. Talk with your healthcare provider to find out if any STD testing is recommended for you.

HIV is not transmitted by day-to-day contact in social settings, schools, or in the workplace, such as:

  • Shaking someone's hand or hugging them.
  • Kissing.
  • Using the same toilet, sheets, towels, or eating utensils, or drinking from the same glass.
  • Playing sports.

What are the symptoms of HIV?

Acute HIV infection: Some people develop flu-like symptoms early after infection, usually within a few weeks or up to a month after contact. Not everyone feels ill though, and symptoms might be mild. During acute HIV infection, there is a large amount of HIV in the blood, and the immune system is beginning to respond to the virus.

Latent or asymptomatic HIV infection: After a few weeks, the level of HIV in the blood decreases and people enter a latent or asymptomatic (no symptoms) stage. During this stage—which can last eight to 10 years—a person usually feels fine. The virus is still active, though, and can be transmitted to others.

Symptomatic HIV infection: The immune system weakens and symptoms related to "opportunistic" infections begin to develop (these are infections that are more likely to occur in someone with a weakened immune system).

AIDS: Untreated, virtually all cases of HIV will lead to AIDS. At this stage, the immune system is severely weakened and serious illnesses emerge. An AIDS diagnosis can be made when someone who has HIV develops an opportunistic infection and/or their CD4 count falls below 200 (this is the number or "count" of CD4 cells in a small sample of blood). A normal CD4 count is between 500 and 1000.

Symptoms might include extreme weight loss, chills and fever, night sweats, fatigue and weakness, sores of the mouth and genitals, diarrhea, and swollen glands. In addition, there are other infections that tend to occur that indicate AIDS.

Are there tests for HIV?

Most HIV tests done in the United States detect substances the body's immune system produces (antibodies) in response to the infection. Some rapid HIV tests can provide results in as little as 20 minutes. HIV also can be detected by testing blood, but some tests use urine or take a swab of fluid from inside your mouth. Many of these tests are done in a lab and it can take a few days or a week to receive results.

Many types of clinics offer HIV tests. There is also a home test, the Home Access HIV-1 Test System.

Most tests can detect the disease two to eight weeks after infection, but in some people this takes longer. The disease can be detected in almost everyone with HIV three months after infection, so it is a good idea for anyone tested earlier than that to have a follow-up test three months after a potential exposure to the virus. In very rare cases, it may take six months or longer for a person to test accurately for HIV. A different test is used for donated blood.

What tests follow an HIV-positive diagnosis?

A healthcare provider usually orders several tests, including one to check viral load (how much HIV is present in the blood), CD4 count (to assess the health of the immune system in fighting infections), and drug resistance (to determine if the individual specific strain of HIV might be resistant to certain medications). These tests not only provide a baseline for future tests but help determine when treatment should begin, along with the patient's overall state of health.

Other common tests for those newly diagnosed with HIV include:

  • Complete blood count.
  • Liver and kidney function tests.
  • Urinalysis.
  • Tests for other STDs and hepatitis.

What are the risk factors for HIV?

A risk factor is the chance that something will harm or otherwise affect a person's health.

Risk factors for HIV include:

  • Engaging in unprotected vaginal, anal, or oral sex.
  • Having sex with multiple partners.
  • Being a man who has sex with men.
  • Using injection drugs and sharing needles, syringes, or "works" with someone who is infected with HIV.

Have an honest and open talk with your healthcare provider and ask whether you should be tested for HIV or other STDs.

How can I lower the chances of getting HIV?

The most effective methods are protecting yourself against exposure to HIV, including sexual abstinence, consistent and correct condom use, abstinence from injection drug use, use of sterile equipment if using injection drugs.

People who are at high risk of getting HIV but do not have HIV can take pre-exposure prophylaxis (PrEP) daily medicines that can significantly lower the chances of getting HIV. PrEP can help keep the virus from establishing a permanent infection when someone is exposed to HIV. PrEP is less effective if it is not taken consistently but, even if some doses are missed, PrEP will still offer significant protection from contracting HIV. People who use PrEP must commit to taking the drug every day and seeing their healthcare provider for follow-up every three months. Talk to your healthcare provider to see if PrEP is right for you. PrEP should be used with other risk reduction strategies, including condoms.

PEP (post-exposure prophylaxis) may be used after being potentially exposed to HIV, to prevent becoming infected. It is only for emergency situations after a single, high-risk event (such as unprotected sex with someone who has HIV or injection drug use). Antiretroviral drugs must be started as soon as possible to be effective-and always within 72 hours of a possible exposure. If you think you have recently been exposed to HIV during sex, through sharing needles, or work to prepare drugs, or if you have been sexually assaulted, talk to your healthcare provider or an emergency room doctor about PEP right away.

How is HIV treated?

There are approximately 30 drugs available to treat HIV, and they are divided into classes based on the way they work against the virus. The recommended treatment for HIV involves a combination or "cocktail" of at least three medications from two or more different classes.

Not everyone uses the same medications to treat HIV. The choice of treatment depends on your general health, the results of any tests ordered by your healthcare provider, the number of pills you feel comfortable taking each day, if you are pregnant or plan to be pregnant soon, and potential side effects. Be sure to ask your healthcare provider any questions you might have about treatment.

I was treated for HIV. When can I have sex again?

You can have sex at any time, however, communication and safe sex is very important. Even if you do not have any symptoms, you can still infect your sex partners. Condoms cannot guarantee HIV will not be transmitted, but using them correctly each time you have sex greatly reduces the risk your partner will be exposed to the virus.

What happens if I don't get treated?

Untreated, virtually all cases of HIV will lead to AIDS. At this stage, the immune system is severely weakened and serious illnesses emerge. An AIDS diagnosis can be made when someone who has HIV develops an opportunistic infection and/or their CD4 count falls below 200 (this is the number or "count" of CD4 cells in small sample of blood). A normal CD4 count is between 500 and 1000.

Talk to your partner

Your current and former sexual partners need to know if you are diagnosed with HIV. This is also true of anyone with whom you have shared needles. Talking about HIV is difficult, but it is the best thing you can do to help others protect their health.

You should tell your sex partner(s) so they can get tested and treated, if necessary. You do not have to do this alone. Your local health department will usually contact partners and talk to them about testing for HIV.


Beyond medications, there are many things you can do to take care of your health.

  • Follow your healthcare provider's instructions and adhere to your treatment plan. Take medications as directed—it is important you do not skip doses.
  • Let your provider know if you have side effects or feel ill from your medications.
  • Ask your provider if there are vaccinations that are recommended for you (such as a flu shot or hepatitis B vaccine).
  • Eat healthy foods, exercise moderately, and get plenty of sleep. Find ways to relax and handle your stress.

Often people with HIV need emotional support and counseling. Family, friends, peers, and support groups can help people who are HIV-positive learn how to take care of themselves and lead a full life.

Did you know? (HIV)

Did You Know?

Did you know?Besides abstaining from all forms of sex, condoms are the best way to protect against STDs.

Learn more about male condoms

Content created by Office of Population Affairs
Content last reviewed on April 2, 2019