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The pandemic that subsided

A new study from the PandemiX research center shows how the 2022 mpox outbreak was brought under control—not by vaccines or immunity, but through information and rapid behavioral changes.
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  • PandemiX Center (Research Centre)
    • This is a picture of Lone Simonsen, Ulrik Hvid and Morten Frisch standing next to each other.
    By: PandemiX Center

    In the summer of 2022—just as the fog of COVID-19 was beginning to lift—the world suddenly faced a new pandemic threat: mpox. Within a few weeks of its first detection in Europe, it had infected tens of thousands worldwide. Yet, although many feared another severe and prolonged epidemic, the outbreak subsided within just a few months. A new study from PandemiX Center, published in PNAS, provides an explanation.

    Unlike COVID-19, which spreads through the air, mpox is transmitted only through very close contact. In 2022, the virus circulated within a network of men at high risk for sexually transmitted infections, and more than one in four mpox cases involved individuals already living with HIV. In August, governments began offering smallpox vaccines to the at-risk group, but by then the epidemic was already on the decline—and no one knew why. A common assumption was that the mpox risk group was so small that it had simply become immune through infection.

    Using a new mathematical model based on detailed data from the Statens Serum Institute’s “Project SEXUS”—one of the world’s largest studies on sexual behavior—PandemiX researchers were able to test different hypotheses about the course of the epidemic. The study shows that targeted international awareness campaigns, which increased knowledge of the disease’s symptoms, had the greatest effect. By informing people about symptoms and transmission routes, more infected individuals isolated themselves quickly, which was sufficient to bring the outbreak under control.

    The study also shows that immunity had almost no effect in slowing the epidemic, which could have been much larger if not for the response from authorities and the public.

    Mpox is an example of a completely different type of pandemic than COVID-19, and our study demonstrates how information and behavioral changes can be just as crucial as vaccines in controlling epidemics. Although the smallpox vaccine cannot take credit for halting the 2022 outbreak, it continues to protect us against recurring outbreaks today