Anyone who has sex without a condom or shares needles can be exposed to HIV, but the virus does not affect all groups equally. Certain sexual behaviors, demographic factors, and geographic realities concentrate risk in specific populations. Understanding where risk is highest helps you assess your own situation and take practical steps to stay protected.
Sexual Behavior Is the Biggest Risk Factor
HIV spreads most efficiently through certain types of sexual contact, and the difference in risk between them is dramatic. Receptive anal intercourse carries a transmission risk of roughly 138 per 10,000 exposures to an infected partner without a condom. Receptive vaginal intercourse, by comparison, carries a risk of about 8 per 10,000 exposures. That makes anal sex approximately 17 times riskier per act.
This biological reality is a major reason why gay, bisexual, and other men who have sex with men (MSM) account for a disproportionate share of new diagnoses. In 2022, MSM accounted for 67% of all new HIV diagnoses in the United States and 86% of diagnoses among men, despite representing a small fraction of the overall population. Insertive anal sex also carries elevated risk (about 11 per 10,000 exposures), meaning both partners face meaningful exposure during unprotected anal intercourse.
Vaginal sex is lower risk per act but still a significant route of transmission, particularly for women. Having multiple sexual partners, overlapping partnerships, or sex with a partner whose HIV status is unknown all increase cumulative risk over time. Sexually transmitted infections like syphilis or herpes can also make transmission more likely by causing inflammation or open sores.
Race and Ethnicity Shape Exposure
HIV diagnosis rates vary sharply across racial and ethnic groups in the U.S., though this reflects social and structural factors rather than biological differences. In 2023, Black and African American people had a diagnosis rate of 41.9 per 100,000, compared to the national average of 13.7 per 100,000. Black women were diagnosed at 11 times the rate of white women (19.6 vs. 1.8 per 100,000). Hispanic and Latina women fell in between at 6.7 per 100,000.
These disparities are driven by unequal access to healthcare, testing, and prevention tools like PrEP. Higher rates of poverty, less insurance coverage, and greater exposure to stigma create conditions where the virus circulates more easily within sexual networks. A person’s individual behavior may be no different from someone in a lower-risk demographic, but if HIV prevalence is higher in their community, each sexual encounter carries a statistically greater chance of exposure.
Where You Live Matters
The U.S. South consistently has the highest HIV diagnosis rates of any region. A group of nine heavily affected Southern states accounted for 38% of all U.S. HIV diagnoses in a single year despite representing a smaller share of the population. Their combined diagnosis rate (24.5 per 100,000) significantly exceeded the national rate (18.0 per 100,000).
Rural and suburban areas in these states face particular challenges. Limited public transportation makes it harder to reach clinics. Fewer qualified providers means longer waits and less specialized care. HIV-related stigma tends to be stronger in smaller communities, discouraging people from getting tested or filling prescriptions. Lower levels of income, education, and insurance coverage in these regions compound the problem. The result: people in the Southern U.S. are not only more likely to be diagnosed with HIV but also have lower five-year survival rates after diagnosis compared to other regions.
People Who Inject Drugs
Sharing needles, syringes, or other injection equipment is a direct route for HIV transmission. Blood remaining in a used needle can carry enough virus to infect the next person who uses it. Outbreaks tied to injection drug use still occur in the U.S., particularly in areas with limited access to clean needle exchange programs.
The risk extends beyond the needle itself. People who use drugs may also engage in higher-risk sexual behavior, trade sex for drugs, or have difficulty maintaining consistent healthcare. These overlapping vulnerabilities make injection drug use one of the most important risk factors outside of sexual transmission.
Age and HIV Risk
Young people between the ages of roughly 13 and 34 account for a large share of new HIV diagnoses. Part of this reflects the higher frequency of new sexual partnerships in younger age groups. But it also reflects gaps in education: younger people may underestimate the seriousness of HIV because modern treatments have made it a manageable condition rather than a death sentence, which can reduce motivation to use condoms or get tested.
Adults over 50 are often overlooked in HIV prevention efforts, yet they represent a growing share of people living with HIV. Older adults are less likely to use condoms, less likely to get tested, and less likely to be offered testing by their doctors. Symptoms of HIV can also be mistaken for normal aging, delaying diagnosis.
Pregnancy and Newborns
A pregnant person with HIV can pass the virus to their baby during pregnancy, childbirth, or breastfeeding. Without treatment, the transmission rate is significant. With proper antiretroviral therapy taken throughout pregnancy and delivery, that risk drops to less than 1%. In the U.S. and Europe, this approach has made perinatal transmission rare, but it depends entirely on early testing and consistent treatment during pregnancy.
How Prevention Changes the Equation
Two tools have fundamentally changed the risk landscape for HIV. The first is PrEP, a medication taken by HIV-negative people to prevent infection. Clinical trials have shown PrEP reduces HIV risk by about 86% among men who have sex with men when taken as directed, either daily or on-demand. PrEP is also effective for people exposed through vaginal sex or injection drug use, though the strongest evidence base comes from studies in MSM populations.
The second is treatment as prevention. People living with HIV who take antiretroviral therapy and maintain an undetectable viral load cannot sexually transmit the virus. This principle, known as Undetectable = Untransmittable (U=U), has been confirmed in large studies of both male-female couples and male-male couples with zero transmissions observed when the HIV-positive partner’s virus was consistently suppressed.
Condoms remain highly effective as well, reducing risk by over 90% when used consistently. The combination of condoms, PrEP for those at higher risk, and effective treatment for people living with HIV means that transmission is largely preventable with the right tools and access. The challenge is making sure those tools reach the communities that need them most.