Speaker
Description
The mpox epidemic in 2022 resulted in more than 100,000 cases across 122 countries. Low levels of case detection continued in 2023, during which New York City (NYC) experienced the largest number of infections per capita among all jurisdictions in the USA. By September 2023, an average of only 2.8 cases were detected per week. In January 2024, the rate increased 4.7-fold to 13.2 cases per week, suggesting a shift in transmission dynamics.
An examination of resurgence cases in NYC revealed no association with vaccine-status. To understand the evolutionary dynamics of the resurgence, we performed Bayesian phylogeographic analysis in BEASTX on 9,659 MPXV genomes, including 878 from the NYC Health Department, sampled between 2022-2024. We find little evidence for prolonged persistence of MPXV in any single jurisdiction within the United States since 2022. Rather, MPXV is repeatedly reintroduced from elsewhere in the USA and around the world. We also identified a large cluster (F.1; n=244), including samples collected between October 2023–December 2024. This cluster originated in NYC (P=0.9957) in September 2023 and became the dominant genotype identified across the USA in 2024, reaching a peak estimated monthly proportion of 72.4% of all cases in the country by August 2024. We performed Bayesian phylogeographic inference on F.1 and Episodic Birth-Death-Sampling (EBDS) on NYC F.1 genomes. This cluster experienced limited exportation from NYC before March 2024, when Re in NYC was >1; after March 2024, it resulted in 13 exportations to jurisdictions and 4 countries, seeding subsequent outbreaks.
Although the late-2023 resurgence of MPXV in NYC in the United States can be predominantly attributed to a single cluster, the continued persistence of this virus since 2022 is the result of repeated introduction and local extinction events. Understanding drivers of sustained transmission can help us understand MPXV persistence and illuminate strategies to control further spread.
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