Monkeypox activity appears to have declined even before widespread vaccination campaigns reached many in vulnerable groups, with a level of herd-like immunity emerging within those populations. This perspective is supported by the European Society for Clinical Microbiology and Infectious Diseases, which has noted downward trends in transmission in recent periods.
The monkeypox outbreak that drew global attention began in 2022. While the disease has existed for decades, sustained person-to-person transmission has not been a characteristic of its history. By the end of that year, more than 85,000 cases had been reported worldwide. Early data identified a higher risk among men who have sex with men and those engaging in casual sexual networks, with infection clusters often associated with particular social and sexual networks. In May 2023, case counts rose more sharply in several regions, followed by a period of decline that began after a few months of monitoring and response.
Several researchers have explored reasons behind the downward trend. Some pointed to vaccination efforts, while others noted declines in smallpox-related diseases in many countries, including Belgium, that occurred before large segments of the at-risk population had been vaccinated. A hypothesis under examination proposed that changes in behavior within key populations could contribute to transmission dynamics, reducing the opportunities for spread.
To investigate this, researchers analyzed data from clinic visits for monkeypox. Among the patients examined, a large majority identified as gay men, and the average number of sexual partners in the preceding three weeks was two. By the epidemic’s end, the typical weekly number of partners within this group had fallen to roughly one. In contrast, among individuals without a smallpox history who were seeking PrEP as a preventive measure against HIV, the number of sexual partners per month appeared to increase over time, suggesting divergent behavioral patterns across groups.
From these observations, researchers inferred that shifts in risk behaviors within core social networks could help explain the observed decline. They cautioned that the data did not fully support a single explanation and emphasized the likelihood of multiple factors at work. The central idea proposed is that the most connected members of the sexual network likely acquired monkeypox early, followed by peripheral members. Immunity developed within the central network could have reduced overall transmission, ultimately contributing to epidemic control. This interpretation underscores the importance of sustained surveillance and adaptive public health strategies that reflect the changing dynamics of at‑risk communities and their behaviors. (European Society for Clinical Microbiology and Infectious Diseases, 2023; Institute for Tropical Medicine observations, 2023; public health surveillance reports, 2023).