Without treatment, syphilis can spread to the brain and nervous system or to the eye, the CDC said. This can happen during any of the stages.
Dr. David Rosenthal, medical director of the Center for Young Adult, Adolescent and Pediatric HIV in Great Neck, N.Y., said syphilis left untreated can be lethal.
One reason more cases of syphilis are known is that doctors are testing for it more among their gay and bisexual patients, Rosenthal said.
“As we started increasing the use of PrEP for HIV prevention, we are seeing gay men every three months that we used to see about every three years, and we are doing syphilis testing and we are finding more cases much earlier,” he explained.
PrEP is a one-pill-a-day preventive treatment for people who don’t have HIV but who are at very high risk of getting it, according to the U.S. Department of Health and Human Services.
“We need to continue to recommend safe sex, particularly using condoms, which are effective in preventing syphilis,” Rosenthal said.
“If people have symptoms, they need to see a doctor as soon as possible, and not have sex with other people while they have their symptoms. In addition, people who are having sex with multiple people should regularly be tested for HIV and other sexually transmitted infections,” he added.