While 75% to 95% of Americans know that diseases such as human papillomavirus (HPV) infection and genital herpes are sexually transmitted, gaps in knowledge about sexually transmitted infections (STIs) remain, including whether there are vaccines against them.
Those findings, from a poll by the Annenberg Public Policy Center (APPC) at the University of Pennsylvania, underscore the need for more education against a backdrop of elevated and rising rates of some STIs, the authors say.
STIs are very common, with roughly 20% of Americans having an STI on any given day in 2018 and 85% infected with HPV at some point in their life. And although case counts of chlamydia, gonorrhea, and syphilis fell in the United States from 2022 to 2024, they are still 13% higher than they were 10 years ago, according to the Centers for Disease Control and Prevention (CDC).
The nationally representative poll of 1,639 US adults was fielded in April 2026. It had a margin of sampling error of ± 3.5 percentage points.
1 in 5 incorrectly implicated toilet seats in STI spread
Nearly half (47%) of respondents said they or someone they know had ever been diagnosed as having an STI, with 72% of them knowing at least two people with that STI.
The proportions of participants who knew that certain diseases are sexually transmitted were high for genital herpes (95%), gonorrhea (94%), syphilis (91%), chlamydia (89%), and HPV (75%, up six percentage points from 2024). Americans were more aware that HIV can be sexually transmitted (92%) than mpox (35%) or Zika (13%), which is mainly mosquito-borne.
While 92% recognize HIV as sexually transmitted, only 33% know it also can be transmitted by breastfeeding.
“Public understanding improves when accurate health information reaches people clearly and consistently,” Ken Winneg, PhD, APPC managing director of survey research, said in the release. “But these findings show continuing gaps in awareness about diseases which can be sexually transmitted such as HPV, mpox, and Zika.”
Americans’ knowledge of common modes of STI transmission was very high, at 97% for vaginal sex, 94% for anal sex, 91% for genital-to-genital contact, and 89% for oral sex. Also, 49% of respondents indicated that STIs can spread by kissing, which although an uncommon route, is possible for syphilis when a sore is present and may be a risk factor for oral gonorrhea. While 20% said sitting on a contaminated toilet seat is a risk factor, the CDC says it isn’t.
“Public understanding is uneven around less common transmission pathways for HIV, in particular,” the release said. “While 92% recognize HIV as sexually transmitted, only 33% know it also can be transmitted by breastfeeding. According to the CDC, HIV can be transmitted during pregnancy, childbirth, or breastfeeding.”
Half incorrectly thought an HIV vaccine exists
Knowledge of which diseases can be prevented by vaccination was spotty, with 68% of respondents correctly indicating that an HPV vaccine is available and 42% correctly identifying mpox as vaccine-preventable.
Likewise, most Americans were unaware that there is no vaccine against HIV (52% unsure or incorrectly thought a vaccine exists), genital herpes (54%), gonorrhea (58%), chlamydia (60%), syphilis (61%), and Zika (81%).
Amid rising rates of syphilis and congenital syphilis, many Americans didn’t know how it can be prevented and treated. Although most (91%) of participants correctly identified syphilis as sexually transmitted, 61% were either unclear whether there is a vaccine against it (44%) or incorrectly indicated that a vaccine exists (17%).
But most respondents (80%) knew that syphilis can be prevented through abstinence, and 78% correctly said that condoms were effective.
There were other encouraging signs that most Americans know basic facts about STIs, including that 93% knew that STIs can spread asymptomatically, 87% rejected the myth that only people with multiple sexual partners get STIs, 83% understood that HIV drugs can control disease progression (a 4 percentage-point decline from 2024), 80% knew that STIs can spread from a pregnant woman to her baby, and 70% knew that HPV can lead to cancer in women. But 14% also incorrectly believed the vaccine leads teens to engage in risky sexual behavior, up from 10% in 2024.