More than three months have passed since the monkeypox outbreak in the United States, and words of welcome are pouring in from the health officials leading the nation’s response. It’s cautious optimism.

The change in tone reflects “recent signs of slowing growth,” according to a CDC technical report released Thursday. These signs are especially noticeable in several major cities where the virus arrived early and spread quickly, including New York City, Chicago and San Francisco.

Federal officials warn it’s too early to make a statement about the country’s impasse. This Labor Day weekend, we will be sending thousands of doses of vaccines to mass gatherings of gay, bisexual and queer people at events like Southern Decadence in New Orleans, Atlanta Black Pride and Pridefest in Oakland. Men who have sex with men who are particularly at risk of exposure and infection to the virus.

The slowdown in some parts of the United States remains an encouraging sign, combined with data on how those most at risk are protecting themselves and getting vaccinated.

“Our numbers are still growing. [but] The rate of increase is low,” Dr. Rochelle Wallensky, director of the Centers for Disease Control and Prevention, told reporters on Aug. 26. work. “

The number of reported cases has been trending downward since mid-August, based on an NPR analysis of data released by the CDC on Wednesday. The numbers are down about 20%, and recent new cases continue to fall.

However, health officials warn that delays in reporting data could create an incomplete picture of the outbreak in recent weeks, making it difficult to know if cases have truly peaked.

And Anne Rimoin, a UCLA epidemiologist who has studied monkeypox for years, said cases could rise again if at-risk health care providers and patients let their guard down and stopped testing and mitigation actions. said it could be done.

“We need to closely monitor the data and continue to move forward to increase testing, increase access to treatment and ensure vaccines are accessible to all at risk,” she says. .

Cases slow down in big cities

In New York City, one of the epicenters of the outbreak, the number of new infections fell by almost 50% from late July to late August. Health officials in San Francisco are also seeing a decline in the number of new cases.

“I’m cautiously optimistic,” said San Francisco City and County Health Officer Dr. Susan Phillippe. “However, we know it will take a lot of work and effort to maintain this downward curve and ensure that the number of cases continues to decline.”

Conditions are also improving in other cities such as Houston and Chicago, where local health leaders say there are signs that infections are leveling off.

Key indicators, such as the average number of cases and the time it takes for cases to double, have declined in the past two weeks, according to Janna Kerins, medical director of the Chicago Public Health Department. “I don’t know if we’re ready to say this outbreak is really over, but all of this is encouraging,” says Kerins.

This change is also consistent with a model released in late August suggesting that the epidemic is declining nationwide.

“There are signs of a significant slowdown, and projections suggest this is going in the right direction,” said Gerald Chowell Puente, professor of epidemiology and biostatistics at Georgia State University. Who is modeling the monkeypox outbreak?

The CDC’s predictions were consistent, saying, “The monkeypox outbreak in the United States is likely to continue to spread very slowly over the next two to four weeks, possibly at a slower rate of growth,” officials said. The staff wrote in a technical report released Thursday.

The decline in parts of the United States reflects what we have already seen in some European countries where the virus was detected a few weeks ago. In both the UK and Germany, the number of daily cases has fallen steadily since late July.In several other countries, including the Netherlands and Italy, the number of new cases has plateaued.

Behavior modification helps

Caitlin Rivers, an epidemiologist at Johns Hopkins University, said that given the size and diversity of the United States, there is still considerable uncertainty about how the outbreak will unfold in different parts of the country. says.

“Case numbers in large, populous states like Texas, California and New York that were hit early in the epidemic, just as other states like Oregon, Virginia and Indiana began to gain momentum. is slowing down,” she wrote in a Substack post on Friday.

Still, infectious disease experts attribute the local and regional slowdowns largely to efforts in these areas to change behavior among homosexuals, bisexuals, and other men who have sex with men. doing.

“Most of us in public health working with this disease believe that most of the decline is due to behavioral changes,” said Weill Cornell Medicine, director of the Cornell Pandemic Prevention and Response Center. says Dr. Jay Varma..

About 80% of monkeypox cases in the United States are now sexually linked, according to Thursday’s technical report. And data published in the CDC’s Morbidity and Mortality Weekly on August 26 shows that the gay and queer communities are modifying their sexual behavior in response to messages about monkeypox. .

In one online survey, about 50% of respondents said the number of sexual partners and one-off sexual encounters has decreased. [or] An accompanying modeling study published by the CDC found that “a 40% reduction in one-off sexual partnerships could slow the spread of monkeypox and reduce infection rates by up to about 10%.” was shown. 30%.

“What this means is that LGBTQIA+ people are actually doing things that reduce risk, and it’s working,” said Dr. Demetre Daskarakis, the White House deputy monkeypox response coordinator. He made the statement at a press conference on May 26.

It’s no surprise that the virus appears to be slowing in the US, as it is in Europe, said Jeffrey Klausner, professor of medicine and infectious disease, population and public health sciences at the Keck University School of Medicine. says Dr. Southern California.

“In most cities, the number of cases will decline, but the decline may not be as fast or sharp as the rise,” Klausner said.

Klausner says that monkeypox mostly stays within a specific, relatively small sexual network. This makes it harder for the virus to maintain momentum as vaccinations increase, people gain immunity from infection, and those at highest risk change their behavior.

“At this time, no one has expressed concern about the spread of infection on college campuses, daycare centers, or other places of close personal contact,” he said.

uncertainty remains

But other experts are less optimistic about the trajectory of the outbreak – at least not yet.

“It’s great to see some declines,” said Rimoin of UCLA. It’s not clear how well it works to prevent infection.

To slow the spread of monkeypox, health officials have taken precautionary measures for members of affected communities, focusing on reducing the number of sexual partners and staying clothed at parties, festivals and raves. We encourage you to continue to take

“I want to be clear,” Daskarakis said on Aug. 26. “Advice on how to reduce the risk of monkeypox exposure is for now, not forever, and with the urgent surge in vaccination to control this, public health and community It’s an important part of the response to the outbreak.”

About 350,000 monkeypox vaccinations have been reportedly given to the CDC.

Still, there are no solid real-world data on how well the monkeypox vaccine approved by the Food and Drug Administration in 2019 protects against infection and transmission. The Biden administration is now pursuing a new strategy of administering the vaccine intradermally to expand supply.

“The experimental data we have on this vaccine suggests it is highly effective in humans,” says Varma. “But what we do know in medicine is that we can never know for sure until we see what’s going on in the real world..”

NPR’s Michaeleen Doucleff contributed to this report.

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