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"HIV" stands for human immunodeficiency virus.

  • H - This particular virus can only infect human beings.
  • I - Immunodeficiency - HIV weakens your immune system by destroying important cells that fight disease and infection. A weak or "deficient" immune system can't fully protect you.
  • V - A virus can only reproduce itself by using the body of its host (for example, a person).

At the end of 2018, about 1.2 million people in the United States were living with HIV. Some groups of people in the United States  are more likely to get HIV than others because of many factors, including the status of their sex partners, their risk behaviors, and where they live.

When people get HIV and don't take HIV medicine, they will typically progress through three stages of disease, one after the other: 1) acute HIV infection; 2) clinical latency, and 3) acquired immunodeficiency syndrome (AIDS).

There are also different types of HIV. It is possible, though rare, for people who have one type of HIV to get another type of HIV also; this is called superinfection.

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General HIV Information

General HIV InformationHIV stands for human immunodeficiency virus. The virus can lead to acquired immunodeficiency syndrome, or AIDS, if not treated. Unlike some other viruses, the human body can’t get rid of HIV completely, even after treatment.

Right now, there is no cure for HIV. But with proper medical care, HIV can be effectively controlled. Treatment for HIV is called antiretroviral therapy or ART. If taken as prescribed, ART can dramatically prolong the lives of many people who have HIV and keep them healthy. Also, people with HIV who take HIV medicine as prescribed and keep an undetectable viral load will not transmit HIV through sex. Before the introduction of ART in the mid-1990s, people with HIV could progress to AIDS (the last stage of HIV infection) in a few years. Today, someone who gets an HIV diagnosis and starts treatment in the early stages of the disease can live nearly as long as someone who does not have HIV.

HIV attacks the body’s immune system , specifically the  CD4 cells  . These special cells help the immune system fight off infections. If HIV isn’t treated, it reduces the number of CD4 cells in the body. This damage to the immune system makes it harder and harder for the body to fight off infections and some other diseases. 

If HIV infection isn’t treated, a person is more likely to get other infections or infection-related cancers. These opportunistic infections or cancers take advantage of a very weak immune system and make the person even sicker.

More information:

Opportunistic illnesses are infections and infection-related cancers that are more common or more severe in people with HIV because their immune systems are damaged. Examples include Kaposi's sarcoma, lymphoma, tuberculosis, and pneumonia.

How HIV Is Transmitted

Only certain body fluids   —from a person with HIV can transmit HIV. The body fluids that can transmit HIV are blood, semen (cum), pre-seminal fluid (pre-cum), rectal fluids, vaginal fluids, and breast milk. For transmission to occur, these fluids must come in contact with a mucous membrane  or damaged tissue or be directly injected into the bloodstream (from a needle or syringe) of a person without HIV.  Mucous membranes are found inside the rectum  , vagina, penis, and mouth.

You can get or transmit HIV only through specific activities. Most commonly, people get or transmit HIV through sexual behaviors and needle or syringe use. However, there are ways to greatly reduce your risk of getting or transmitting HIV from these activities, such as

Learn more about how HIV is and isn’t transmitted in the United States.

More Information

HIV is most often transmitted by

  • Having sex with someone who has HIV without using a condom or taking medicine to prevent or treat HIV.
    • Anal sex is the riskiest type of sex for getting or transmitting HIV. For the HIV-negative partner, receptive anal sex ( bottoming  ) is much riskier than insertive anal sex ( topping   ).
    • Either partner can get HIV through  vaginal sex, though it is less risky for getting HIV than anal sex.
  • Sharing needles, syringes or other injection equipment (for example, cookers) with someone who has HIV. HIV can live in a used needle for up to 42 days depending on temperature and other factors.

Less commonly, HIV may be transmitted by

  • Pregnancy, childbirth, or breastfeeding if the mother has HIV— HIV can be passed from mother to child during pregnancy, birth, or breastfeeding. The risk can be high if a mother with HIV is not taking HIV medicine (called antiretroviral therapy, or ART). But recommendations to test all pregnant women for HIV and start HIV treatment immediately have lowered the number of babies born with HIV.
  • Being stuck with an HIV-contaminated needle or other sharp object. This is a risk mainly for health care workers.

In extremely rare cases, HIV may be spread by

  • Oral sex— putting the mouth on the penis ( fellatio  ), vagina ( cunnilingus  ), or  anus   (rimming). Generally, there is extremely low to no risk of getting HIV from oral sex. But the risk is higher if blood, open sores, or other sexually transmitted diseases are present and the person with HIV has a detectable viral load.
  • Receiving blood transfusions, blood products, or organ/tissue transplants that are contaminated with HIV. This risk is extremely low because of thorough testing of the US blood supply and donated organs and tissues.
  • Eating food that has been pre-chewed by someone with HIV. When a caregiver with HIV pre-chews food, infected blood can mix with the food, but this is very rare. The only known cases of getting HIV from pre-chewed food are among infants.
  • Being bitten by a person with HIV. Each of the very small number of documented cases has involved severe trauma with extensive tissue damage and the presence of blood. There is no risk of transmission if the skin isn’t broken.
  • Contact between broken skin, wounds, or mucous membranes and HIV-infected blood or body fluids contaminated with blood. Reports of this have also been extremely rare.
  • Deep, open-mouth kissing if both partners have sores or bleeding gums and blood from the partner with HIV gets into the bloodstream of the partner who doesn’t have HIV. HIV isn’t spread through saliva. Transmission through kissing alone is extremely rare.

HIV isn’t transmitted by

  • Saliva, tears, or sweat (unless it is mixed with the blood of a person with HIV).
  • Hugging, shaking hands, sharing toilets, sharing dishes, or closed-mouth or “social” kissing with someone who is HIV-positive.
  • Other sexual activities that don’t involve the exchange of body fluids (e.g., touching).
  • Mosquitoes, ticks or other blood-sucking insects. 

HIV in the United States

About 1.2 million people in the United States have HIV. In 2018, nearly 38,000 people received an HIV diagnosis in the United States and dependent areas. Though the number of new HIV diagnoses has declined over the last few years, the number of people who have HIV has been increasing because people with HIV are now living longer.

In 2018, 81% of new diagnoses in the United States and dependent areas were among adult and adolescent men and 19% were among adult and adolescent women. Most new HIV diagnoses among women were from heterosexual contact (85%), and another 15% were from injection drug use. By age, 21% of new HIV diagnoses in 2018 were among young people aged 13 to 24, 36% were among people aged 25 to 34, 19% were among people aged 35 to 44, 14% were among people aged 45 to 54, and 10% were among people aged 55 and older.

When you live in a community where many people have HIV infection, the chances of having sex with someone who has HIV are higher. This interactive atlas allows you to see the rates of HIV infection (“prevalence ”) in different US communities. Within any community, the prevalence of HIV can vary among different populations.

HIV is transmitted when engaging in risky behaviors, like (1) having anal or vaginal sex without a condom or without taking medicine to prevent or treat HIV  and (2) sharing needles, syringes or other injection equipment (for example, cookers).  Certain cultural and societal factors can also play a part in HIV risk. These factors include poverty, lack of educational opportunities, lack of access to health care, homophobia , stigma, and racial/ethnic or gender discrimination.

Overall, data show

  • Gay, bisexual, and other men who have sex with men (MSM) have the largest number of new HIV diagnoses in the United States and dependent areas.
    More information: About 4% of the US male population is gay or bisexual, but gay and bisexual men accounted for 86% of all new HIV diagnoses among men and 69% of all diagnoses in 2018. The number of new HIV diagnoses among gay and bisexual men was highest in men aged 25 to 34. Young black/African American gay and bisexual men (aged 13 to 24) accounted for 51% of new diagnoses among all young gay and bisexual men and 34% of new diagnoses among all black/African American gay and bisexual men.

    More information:Many factors may increase HIV risk for some gay, bisexual, or other men who have sex with men (MSM). For example,

    • Homophobia, stigma, and discrimination may place gay and bisexual men at risk for multiple physical and mental health problems and may affect whether they seek and are able to obtain high-quality health services.
    • Most gay and bisexual men get HIV from having anal sex without using condoms or taking medicines to prevent or treat HIV. Anal sex is the riskiest type of sex for getting or transmitting HIV. Receptive anal sex is 13 times as risky for getting HIV as insertive anal sex.
    • Socioeconomic factors, such as having limited access to quality health care, lower income and educational levels, and higher rates of unemployment and incarceration, may place some gay and bisexual men at higher risk for HIV.
  • Blacks/African Americans and Hispanics/Latinos are disproportionally affected by HIV than other racial and ethnic groups.
    More information: About 13% of the US population is black/African American, but they accounted for 42% of new HIV diagnoses in 2018. Similarly, although about 18% of the total US population is Hispanic/Latino, they accounted for 27% of new HIV diagnoses in 2018.

    More information: Many cultural, socioeconomic, and health-related factors may increase HIV risk for some African Americans and Hispanics/Latinos. For example,

    • Stigma, fear, discrimination, and homophobia may place many African Americans and Hispanics/Latinos at higher risk for HIV.
    • The poverty rate is high among African Americans. The socioeconomic issues associated with poverty—including limited access to high-quality health care, housing, and HIV prevention education—directly and indirectly increase the risk for getting HIV and affect the health of people with and at risk for HIV.
    • Similarly, poverty, migration patterns, lower educational level, and language barriers may make it harder for some Hispanics/Latinos to get HIV testing and care. Undocumented Hispanics/Latinos may be less likely to use HIV prevention services, get an HIV test, or get treatment for HIV because of concerns about being arrested and deported.
  • Transgender women who have sex with men are among the groups at highest risk for HIV infection. 
    More information: Because we don’t have complete data for this population, we don’t know how many transgender women in the United States have HIV. However, data collected by local health departments and scientists studying these communities show high levels of HIV infection, with a recent study reporting that an estimated 14% of transgender women have HIV.

    More information: Many cultural, socioeconomic, and health-related factors may increase HIV risk for some transgender people. For example,

    • Discrimination and social stigma can reduce access to education, jobs, health care, and housing.
    • Commercial sex work, mental health issues, incarceration, homelessness, unemployment, and high levels of substance misuse compared to the general population, as well as violence and lack of family support, may put transgender people at risk for HIV.
    • Health care providers may be insensitive to transgender identity or sexuality, which can make it harder for transgender people who have HIV to seek health care. Research shows that even if transgender women seek care, they are less likely to take antiretroviral therapy (ART) than nontransgender (cis-gender) people with HIV, though transgender women are just as likely to have health insurance coverage. The lower rates of taking ART could be because of provider decisions or because transgender people are concerned about potential interactions between ART and hormones.
  • People who inject drugs remain at significant risk for getting HIV.

    More information: In 2018, 7% of new HIV diagnoses in the United States and dependent areas were attributed to injection drug use and another 3% to male-to-male sexual contact and injection drug use (men who reported both risk factors). Of the HIV diagnoses attributed to injection drug use, 58% were among men and 42% were among women.

    More information: Many factors may increase HIV risk for some people who inject drugs (PWID). For example,

    • The high-risk practices of sharing needles, syringes, and other injection equipment (for example, cookers) are common among PWID.
    • PWID may also engage in risky sexual behaviors, such as having sex without a condom or without medicines to prevent or treat HIV, having sex with multiple partners, or trading sex for money or drugs.
    • The prescription opioid and heroin epidemic has led to increased numbers of PWID, placing new populations at increased risk for HIV. The epidemic has disproportionately affected nonurban areas, where HIV prevalence rates have historically been low. These areas have limited services for HIV prevention and treatment and substance use disorder treatment.
    • Social and economic factors limit access to HIV prevention and treatment services among PWID.
    • PWID may face stigma and discrimination. Often, injection drug use is viewed as a criminal activity rather than a medical issue that requires counseling and rehabilitation. Stigma and mistrust of the health care system may prevent PWID from seeking HIV testing, care, and treatment.

 

Stages of HIV Infection

When people get HIV and don’t receive treatment, they will typically progress through three stages of disease. HIV medicine, known as antiretroviral therapy (ART), helps people at all stages of the disease if taken as prescribed. People with HIV should be begin ART as soon as possible after diagnosis. Treatment can slow the disease or keep it from getting worse. People with HIV who take HIV medicine as prescribed and keep an undetectable viral load can stay healthy and will not transmit HIV to their HIV-negative sex partners.
Stages of HIV Infection

Stage 1: Acute HIV infection

Within 2 to 4 weeks after someone gets HIV, they may have a flu-like illness, which may last for a few weeks. This is the body’s natural response to infection. This stage is called acute HIV infection. When people have acute HIV infection, they have a large amount of virus in their blood and are extremely contagious. But people with acute infection often don’t know they have HIV because they may not feel sick right away or at all.  To know whether someone has acute infection, either an antigen/antibody or nucleic acid (NAT) test is necessary. If you think you have been exposed  to HIV through sex or drug use and you have flu-like symptoms, visit a health care provider or clinic immediately and ask for a test to diagnose acute infection.

Stage 2: Clinical latency (HIV inactivity or dormancy)

This period is sometimes called asymptomatic HIV infection or chronic HIV infection. During this phase, HIV is still active but the amount of HIV in the body grows very slowly. People may not have any symptoms or get sick during this time. For people who aren’t taking HIV medicine (ART), this period can last a decade (10 years) or longer, but some may progress through this phase faster. People who are taking HIV medicine as prescribed may be in this stage for several decades. It’s important to remember that you can still transmit HIV to others during this phase unless you are taking HIV medicine and keep an undetectable viral load. If you take HIV medicine as prescribed and keep an undetectable viral load, you will stay healthy and will not transmit HIV to your HIV-negative sex partners. At the end of this phase, if you are not taking your HIV medicine as prescribed, your viral load can increase while your CD4 cell count decreases.  As this happens, you may begin to have symptoms as the virus levels increase in your body, and you move into Stage 3.

More Information CD4 cells cause the body’s immune system to start working to fight off infections. HIV attacks the body’s CD4 cells so that it’s harder for the immune system to fight off viruses or infections.

 

Stage 3: Acquired immunodeficiency syndrome (AIDS)

AIDS is the most severe phase of HIV infection. If you have not been effectively treating you HIV with HIV medicines, you will most likely reach Stage 3, called AIDS.  People with AIDS have badly damaged immune systems and get an increasing number of severe HIV-related illnesses, called opportunistic illnesses.

More information: Opportunistic illnesses are infections and infection-related cancers that are more common or more severe in people with HIV because their immune systems are damaged. Examples include Kaposi's sarcoma, lymphoma, tuberculosis, and pneumonia.

Without treatment, people with AIDS typically survive about 3 years. Common symptoms of AIDS include chills, fever, sweats, swollen lymph glands, weakness, and weight loss. People receive an AIDS diagnosis when their CD4 cell count drops below 200 cells in a cubic millimeter of blood (200/mm3) or if they develop certain opportunistic illnesses. People with AIDS can have a high viral load and a high chance of transmitting HIV.

 

Infection with more than one HIV type (superinfection)

What is HIV superinfection? HIV superinfection is when a person with HIV also gets another type, or strain, of the HIV virus. The new strain of HIV can replace the original strain or remain along with the original strain. This usually happens when a person first gets HIV, or soon after they get a new strain.

 

What we know about super-infection

What we know about super-infection

Superinfection may cause some people to get sicker faster because the medicine (antiretroviral therapy or ART) they’re taking to treat the original strain of HIV doesn’t work on the new strain.
 
It’s hard to know how often superinfections occur. Research suggests that a hard-to-treat superinfection is rare, less than 1% to 4%. Taking ART can help protect someone from getting a superinfection. In fact, if two people have HIV and both keep an undetectable viral load , neither partner will transmit HIV to the other through sex. 

What you can do

If you have HIV, take HIV medicine and use condoms or other barrier methods  the right way, every time you have sex to protect yourself and your partners from superinfection.

Content last updated Jun 14, 2022

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