S.T.D. Rates Are Falling, Data Show. That May Not Be Good News.

Even if sex has declined, researchers question how long it can remain suppressed. Dr. Lehmiller noted that online dating apps report record business. Whether that translates into sexual activity rather than virtual meet-ups is unclear, he said. If people are returning to normal levels of encounters, they may not want to admit it.

“There is shaming about traveling, social events and gatherings during the pandemic, so sex and dating is seen as part of that,” he said.

For now, triage at clinics is pervasive. Pre-pandemic, the San Francisco City Clinic would typically send more than a hundred specimens to be processed daily at the health department laboratory. Because those supplies have dwindled, the clinic is resorting to a smaller, more expensive backup system, that can only process several dozen gonorrhea and chlamydia tests a day, said Dr. Ina Park, an associate professor of community and family medicine at the University of California San Francisco School of Medicine.

Men who take PrEP to prevent H.I.V. transmission should be screened for S.T.D.s every three months, but many clinics have spaced out those screenings to every six months, she said.

A Michigan colleague who had run out of urine testing kits for chlamydia and gonorrhea, she said, was returning to techniques that had been replaced almost 20 years ago: “using older swabs that have to be placed a few centimeters inside the urethra of the penis and twirled around to obtain a specimen. It’s highly unpleasant for the patient and doesn’t encourage them to return for testing,” Dr. Park said.

“I’m concerned that this will worsen mistrust in the medical establishment, which is already an issue with some of the patients we serve,” added Dr. Park, the author of “Strange Bedfellows,” a book out in February on the history and science of sexually transmitted diseases.

David C. Harvey, executive director of the National Coalition of STD Directors, said clinics are trying to come up with creative solutions, such as telemedicine visits. In a few districts where the biggest challenge is reduced clinic access, administrators are trying out test kits that allow patients to collect specimens at home, which they then mail to labs. And some clinics are working with pharmacies that can draw blood and have standing orders for some medications. Public health officials see these innovations as a silver lining that may continue after the pandemic abates.