A major mpox outbreak in the United States reached its peak during the summer of 2022. More than a year since its peak, mpox continues to spread at low levels, with as many as 60 cases per week nationally. The persistence of mpox is surprising, considering that outbreaks in historically non-endemic countries tend to be short-lived. OHT researchers built upon a previously established network epidemic model of mpox to investigate three different hypothesized factors that could contribute to its persistence. These mechanisms included the potential underdetection of mpox cases, resulting from both inadequate surveillance and the possibility of asymptomatic transmission; the waning of vaccine-derived protection; and the waning of infection-derived immunity. The researchers modeled each mechanism separately and fit these simulated outbreaks to the outbreaks in Chicago, New York City, and San Francisco.  

The underdetection mechanism produced the best-fitting models. Additionally, a  sensitivity analysis indicated that varying the proportion of undetected cases significantly altered the duration of the simulated outbreaks. Outbreaks with a greater fraction of undetected cases produced longer outbreaks than those with a smaller fraction of undetected cases. In contrast, modifying the duration of immunity provided by vaccination or previous infection had a negligible effect on outbreak length. Consequently, these findings suggest a critical need to reevaluate and strengthen our surveillance strategies for mpox, to better understand and capture the true extent of its transmission within communities. 

MInD (Centers for Disease Control and Prevention)