When the number of monkeypox cases in Europe began to decline, researchers wondered if it was real. Some people were worried that people wouldn't get tested because of the strict isolation requirements. Catherine Smallwood is the monkeypox incident manager at the WHO Regional Office for Europe.

The decline is clear. During the peak in July, WHO Europe reported more than 2000 cases a week. The other major epicenter of the outbreak in the Americas has seen a drop in numbers. Smallwood says there is a decline.

Vaccines, behavior change among men who have sex with men, and immunity after natural infections are all playing a role in the decline. We've debated this a lot inside.

It's important that the answer is important. The goal WHO Europe is pushing for is to eliminate the virus outside endemic countries in Africa.

In the United Kingdom, at least, vaccination campaigns have played a minor role according to a model published as a preprint this month. Even though campaigns only started in July, Monkeypox's reproductive number was going to fall by mid- June. The pattern was seen in several European countries.

Behavior change and immunity from infections are left. According to a survey conducted by the U.S. Centers for Disease Control and Prevention, half of MSM have reduced their sexual contact. As awareness of the disease increased, people were more likely to seek treatment early and avoid sex. According to Volz, the data presented by the UK Health Security Agency suggests that syphilis and other sexually transmitted infections have declined, but that's not conclusive.

The most sexually active men may have the biggest impact on immunity. MSM and their sexual networks have been affected by Monkeypox due to the fact that some people have a lot of sexual contacts. Jacco Wallinga is an epidemic modeler at the Dutch National Institute for Public Health and the Environment. The depletion of susceptibles due to natural infections is very rapid if the person has a lot of sexual contacts. The brand agrees. Half of the estimated 1000 people in the United Kingdom who have 120 sexual partners per month or more may have gotten STDs by the peak. Brand theorizes that infections among this small part of the MSM population can't explain the decline on their own. He doesn't think it's plausible as behavior change plays a role

Europe and the Americas have both seen a decline in monkeypox cases.

0 1000 2000 3000 4000 5000 9 May 6 Jun. 4 Jul. 1 Aug. 29 Aug. 26 Sep. Cases per week Europe Americas

Smallwood is concerned that MSM who feel reassured by the case numbers may go back to their previous behavior. She says that the vaccine is more important now than it was at the peak of the epidemic. Brand's U.K. model suggests that vaccinations should prevent a resurgence even if there is a slight increase in cases in the coming months. He doesn't think there's room for complacence at this point

It may be hard to eliminate the virus from nonendemic countries. Smallwood says that the last part is the most difficult. Stigma and discrimination are some of the reasons She says that in a lot of countries, people with infections will not be presenting solely because they are concerned about how they will be treated. It has become clear that some people have infections that are not life threatening and could be passed on to someone else.

Reintroductions from sexual networks in countries where the virus is still circulating in humans would remain a threat even if Europe or the US eliminated the virus. The source of the virus will remain the same as it has been for decades: the animal species in Africa. Smallwood says that this isn't an outbreak that just needs to be fixed.