What's behind dramatic drop in monkeypox cases in the US

After weeks of rising cases, the monkeypox outbreak appears to be significantly slowing down in the United States.

As of Sept. 21, the latest date for which data is available, the seven-day case average was 197, according to the Centers for Disease Control and Prevention.

This is a 50% drop from the seven-day rolling average of 394 recorded one month ago, the data shows.

Similar situations are occurring in cities across the U.S. In New York City -- the epicenter of the outbreak -- the seven-day average of infections has declined by 85.7% over the course of a month from 35 to five, as of Sept. 23, according to data from the city's Department of Health & Mental Hygiene.

Additionally, in Los Angeles, the seven-day average has fallen by 80.5% from 36 to seven, as of Sept. 26, Los Angeles County Department of Public Health data shows.

Dr. William Schaffner, a professor of preventive medicine at the Vanderbilt University Medical Center, told ABC News there are two reasons why monkeypox infections are trending downward.

One reason is that at-risk people have changed their behaviors.

The outbreak has primarily been concentrated in men who have sex with men, a group that includes people who identify as gay, bisexual, transgender and nonbinary, although health officials have said anyone -- regardless of sexual orientation -- is at risk if they have direct contact with an infected patient.

Schaffner said those at risk have been inundated with information about how to reduce their risk and have followed doctors' advice.

"There's been a terrific amount of public health education that's gone out and it's gone out particularly to the MSM community and the LBGTQ community that's been primarily affected," he said. "So, you have a target population, they've been literally flooded, in some instances, with information about monkeypox, and what you as an individual can do to protect yourself against becoming infected."

Schaffner added, "And so a lot of the communication I think, has been successful. And here's the inferential part, I think people may have altered some of their behaviors, to reduce their risk."

A joint survey from the CDC, Emory University and Johns Hopkins University found about one-half of gay, bisexual, and other men who have sex with men reduced their number of sexual partners, one-time anonymous partners, and reduced use of dating apps.

The second reason for the decline is vaccinations, Schaffner said.

As of Sept. 20, more than 684,000 JYNNEOS vaccine doses have been distributed in the U.S., CDC data shows. As of the week ending Sept. 10, the number of second doses administered are more than the number of first doses, meaning people are returning to receive full protection.

Last month, to increase the number of doses available, the U.S. Food and Drug Administration authorized a new strategy to inject the vaccine intradermally, just below the first layer of skin, rather than subcutaneously, or under all the layers of skin -- allowing one vial of vaccine to be administered as five separate doses rather than a single dose.

"We had data that told us it would be as effective and that appears also to be working," Schaffner said. "[There's been] acceptance of the vaccine by people in the target population and we've developed the capacity to get it out, make it available easily without stigma."

However, Schaffner said the battle is not over yet and there should be a sustained effort on the part of public health officials, clinicians and community leaders to keep spreading information on the seriousness of monkeypox and how to reduce risk as well as how to get vaccinated.

"This will require sustained attention for some time," he said. "It's wonderful that things look as though they're plateauing and declining, but we have to keep attention on wherever this disease is, and we have to keep our public health and communications efforts out there."

"It's not 'mission accomplished.' We have to keep being careful and take advantage of the vaccine," Schaffner added.