Drug-resistant gonorrhea, a form of the widespread sexually transmitted infection, is considered an urgent health threat worldwide. The United States has just lost its ability to detect it.

Among the Centers for Disease Control and Prevention employees fired on Tuesday were 77 scientists who, among other work, gathered samples of gonorrhea and other S.T.I.s from labs nationwide, analyzed the genetic information for signs of drug resistance, and readied the samples for storage at a secure facility.

No other researchers at the agency have the expertise, or the software, to continue this work. The abrupt halt has stranded about 1,000 samples of gonorrhea and other sexually transmitted pathogens that had not yet been processed, and perhaps dozens more headed to the agency.

There are as many as 30 freezers full of samples that now have no custodians, said one senior C.D.C. official who spoke on condition of anonymity for fear of retaliation.

“We were just really shut down midair, like there was no warning,” the official said. “It was just completely unplanned and chaotic.”

The C.D.C.’s work on S.T.I.s had taken on greater urgency in the past few years as rates of new infections soared. More than 2.4 million new S.T.I.s were diagnosed in 2023, about one million more than 20 years ago.

Nearly 4,000 babies were born with congenital syphilis in 2023. About 280 were stillborn or died soon after.

“Whoever got rid of the lab just doesn’t understand how important the lab is,” said another senior C.D.C. official who spoke on condition of anonymity.

About 600,000 new gonorrhea cases were diagnosed in the United States in 2023. The bacteria that cause gonorrhea, called Neisseria gonorrhoeae, spread through sexual contact to the genitals, rectum and throat. Left untreated, it can cause infertility and sterility, blindness in infants or even death.

Gonorrhea has become resistant to nearly every available antibiotic, leaving a single class that still snuffs it out. The most powerful defense combines a shot of ceftriaxone with azithromycin, but some evidence hints that gonorrhea is evolving to sidestep even that treatment.

Over more than 25 years, the C.D.C. lab archived about 50,000 gonorrhea samples — the largest collection in the world — which allow scientists to track how the pathogen has changed over time. It’s not clear what will happen to the samples.

One new public health strategy makes it even more important for the nation to track gonorrhea, said Dr. Jenell Stewart, an infectious diseases physician at Hennepin Healthcare in Minneapolis.

In a bid to combat resurgent syphilis and chlamydia, the C.D.C. recommended last year that gay and bisexual men and transgender women take doxycycline, a widely used antibiotic, within 72 hours of unprotected sex.

Cities like San Francisco and Seattle that had earlier endorsed the practice, called doxy-PEP, have already seen drastic drops in the rates of those infections.

But researchers are worried that widespread use of doxycycline might increase resistance to the entire class of antibiotics, called tetracyclines. A few studies suggest there may be reason to worry.

Harvard University researchers last month analyzed more than 14,000 genetic sequences generated by C.D.C. researchers and found that the proportion of gonorrhea bacteria with antibiotic resistance increased to more than 35 percent last year, from less than 10 percent in 2020.

The federal scientists who produced that data and made it publicly available have all been fired. “Without public health money and infrastructure, I’m not sure who if anyone will take up the torch to monitor gonorrhea resistance,” Dr. Stewart said.

“This is a huge loss,” she added.

Dr. Stewart and a colleague spent two years preparing the protocol and an app to study doxy-PEP in cisgender women and monitor gonorrhea resistance.

The study was supported by the Adolescent Medicine Trials Network, whose funding was slashed last month.

At least five other grants to study doxy-PEP have been terminated, along with a variety of grants at the National Institutes of Health aimed at preventing S.T.I.s, including H.I.V.

Any lab can test for S.T.I.s, but commercial tests cannot determine whether gonorrhea will respond to available treatments. C.D.C. scientists developed the only such test, and provided funding and training to a few dozen labs on the sophisticated testing.

Samples were sent to the agency for confirmation. Without the agency scientists, testing for drug sensitivity will most likely cease, several experts said.

“We cannot have a national surveillance system without a national lab,” said one scientist who leads a C.D.C.-funded lab but did not wish to be identified without authorization to speak to the media.

C.D.C. scientists were also helping to develop alternatives to the nation’s outdated syphilis test. It cannot identify an active infection, only whether someone was ever infected. The agency has three large contracts to develop new rapid syphilis tests.

But without expertise and the samples from C.D.C. scientists, it’s unclear whether that work can continue, said a senior official with knowledge of the situation.

The fired scientists had about 1,400 years of field experience between them. The official said, “These were highly trained people that are not replaceable easily.”