HIV risk factors: how HIV spreads and who is at higher risk

What HIV and AIDS are

HIV stands for human immunodeficiency virus. It attacks and destroys the infection-fighting CD4 cells of the immune system, which makes it hard for the body to fight off infections, illnesses and certain cancers (NIH HIVinfo). AIDS (acquired immunodeficiency syndrome) is the most advanced stage of HIV infection (NIH HIVinfo). Not everyone with HIV develops AIDS (MedlinePlus).

How HIV spreads

HIV can be passed through certain body fluids: blood, semen, pre-seminal fluid, vaginal fluids, rectal fluids and breastmilk (NIH HIVinfo). In the United States it is passed mainly by (NIH HIVinfo):

• having anal or vaginal sex with someone who has HIV without using a condom or when that person is not taking medicines to prevent or treat HIV
• sharing injection drug equipment, such as needles or syringes, with someone who has HIV

MedlinePlus says unprotected vaginal or anal sex is the most common way HIV spreads (MedlinePlus). HIVinfo also lists accidental needle sticks, sharing personal items that may have blood on them (such as razors or toothbrushes), sharing needles for tattooing and eating prechewed food. Oral sex is less likely to pass HIV but can in rare cases (NIH HIVinfo). A baby can get HIV during pregnancy, childbirth or breastfeeding, which is called perinatal transmission (NIH HIVinfo).

You cannot get HIV by shaking hands with or hugging a person who has HIV, or from dishes, toilet seats or doorknobs they have used. HIV is not spread through the air or water or by mosquitoes, ticks or other insects (NIH HIVinfo).

Who is at higher risk

Anyone can get HIV, but MedlinePlus names these groups as having a higher risk (MedlinePlus):

• people who have another sexually transmitted infection (STI), which can raise the risk of getting or spreading HIV
• people who inject drugs with shared needles
• gay and bisexual men
• Black/African Americans and Hispanic/Latino Americans, who make up a higher proportion of new HIV diagnoses and people with HIV compared with other races and ethnicities
• people who engage in risky sexual behaviors, such as not using condoms or medicine to prevent or treat HIV

Stigma, discrimination, income, education and geographic region can also affect a person's risk (MedlinePlus).

HIVinfo gives these examples of people whose chances of getting HIV may be higher because of certain behaviors or situations (NIH HIVinfo):

• people who have unprotected sex with multiple partners or with strangers (such as sex workers)
• health care workers who may come in contact with bodily fluids
• people who travel to areas where HIV is common (such as sub-Saharan Africa)
• men who have sex with men
• people who inject drugs, especially those who share needles

Having an untreated STI can increase the likelihood of HIV transmission, and the chance of coming into contact with HIV or another STI may rise with more sexual partners or partners you aren't familiar with (NIH HIVinfo). Our chlamydia and gonorrhea screening and syphilis screening checks cover testing for common STIs. HIV and the viral hepatitis infections share some routes, see hepatitis B and hepatitis C risk factors.

Early symptoms

Within 2 to 4 weeks after infection, some people have flu-like symptoms such as fever or chills, lasting a few days to several weeks (NIH HIVinfo). MedlinePlus lists fever, chills, rash, night sweats, muscle aches, sore throat, fatigue, swollen lymph nodes and mouth ulcers (MedlinePlus). Having these symptoms does not mean you have HIV, because other illnesses cause the same ones (NIH HIVinfo).

Some people do not feel sick in the early stages, and without treatment the chronic stage often has no symptoms. The only way to know for sure is to get tested (MedlinePlus). Without treatment, HIV can be passed on at any stage, even if the person has no symptoms (NIH HIVinfo).

Who should get tested

HIVinfo reports that CDC recommends everyone aged 13 to 64 get tested for HIV at least once as part of routine health care. People with more risk factors should generally be tested each year, and sexually active men who have sex with men may benefit from testing more often, such as every 3 to 6 months (NIH HIVinfo). All pregnant women should be tested (NIH HIVinfo).

For people older than 64, a provider may recommend testing if they have risk factors such as (NIH HIVinfo):

• vaginal or anal sex with someone who has HIV or whose HIV status you do not know
• injecting drugs and sharing needles, syringes or other drug equipment
• exchanging sex for money or drugs
• having an STI, such as syphilis
• having sex with anyone who has any of these risk factors

An estimated 15 percent of people with HIV in the United States do not know they have it, and CDC estimates that about 40 percent of new HIV diagnoses are transmitted by people who are not aware of their status (NIH HIVinfo). Our HIV screening check walks through the USPSTF screening advice.

How to lower your risk

HIVinfo lists these steps (NIH HIVinfo):

• get tested, and talk to your partners about testing for HIV and other STIs
• use condoms correctly every time you have sex
• know your sexual partners
• talk to your health care provider about pre-exposure prophylaxis (PrEP)
• do not share injection drug equipment

PrEP is an HIV prevention option if you do not have HIV but are at increased risk, for example if your partner has HIV or if you inject drugs (NIH HIVinfo). It means taking a specific HIV medicine on a routine schedule, daily for pills or by schedule for injections, before an exposure (NIH HIVinfo). Our HIV PrEP eligibility check covers who the USPSTF says should be considered.

PEP is a short course (28 days) of HIV medicines started within 72 hours after a possible exposure. It should not be used regularly (NIH HIVinfo).

Treatment and passing HIV on

There is no cure for HIV, but it can be treated with medicines called antiretroviral therapy (ART), which can make it a manageable chronic condition (MedlinePlus). ART is recommended for everyone with HIV (NIH HIVinfo). Most people with HIV live long and healthy lives if they start ART as soon as possible and stay on it (MedlinePlus).

People with HIV who keep an undetectable viral load have no risk of passing HIV to their partners through sex. This is known as Undetectable = Untransmittable, or U=U (NIH HIVinfo). HIV medicines do not prevent other STIs (NIH HIVinfo).

Common questions

Can I get HIV from oral sex?

HIVinfo says it is less likely than vaginal or anal sex but can occur in rare cases (NIH HIVinfo).

I tested negative. Does that mean I am not at risk?

A negative test shows you do not have HIV. If you have risk factors, HIVinfo says to keep taking steps such as using condoms during sex, and you can consider PrEP (NIH HIVinfo). Each test also has a window period, the time between a possible exposure and when the test can accurately detect HIV (NIH HIVinfo), so ask your provider when to test again.

Can mosquitoes or everyday contact spread HIV?

No. HIV is not spread by mosquitoes, ticks or other insects, through air or water, or by hugging, shaking hands or sharing dishes and toilet seats (NIH HIVinfo).