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. 2024 Mar 26;229(Supplement_2):S305-S312.
doi: 10.1093/infdis/jiad533.

Preparing for Mpox Resurgence: Surveillance Lessons From Outbreaks in Toronto, Canada

Herveen Sachdeva  1   2 , Rita Shahin  1   2 , Sylvia Ota  1 , Sandra Isabel  3   4 , Chand S Mangat  5 , Rebecca Stuart  1 , Shovita Padhi  1   2 , Allison Chris  1   2 , Sharmistha Mishra  6   7   8   9   10 , Darrell H S Tan  6   7   8   10 , Tom W Braukmann  3 , AliReza Eshaghi  3 , Edgard M Mejia  5 , Nikho A Hizon  5 , Michael Finkelstein  1   2
Affiliations

Preparing for Mpox Resurgence: Surveillance Lessons From Outbreaks in Toronto, Canada

Herveen Sachdeva et al. J Infect Dis. .

Abstract

Background: With many global jurisdictions, Toronto, Canada, experienced an mpox outbreak in spring/summer 2022. Cases declined following implementation of a large vaccination campaign. A surge in early 2023 led to speculation that asymptomatic and/or undetected local transmission was occurring in the city.

Methods: Mpox cases and positive laboratory results are reported to Toronto Public Health. Epidemic curves and descriptive risk factor summaries for the 2022 and 2023 outbreaks were generated. First- and second-dose vaccination was monitored. Mpox virus wastewater surveillance and whole genome sequencing were conducted to generate hypotheses about the source of the 2023 resurgence.

Results: An overall 515 cases were reported in spring/summer 2022 and 17 in the 2022-2023 resurgence. Wastewater data correlated with the timing of cases. Whole genome sequencing showed that 2022-2023 cases were distinct from 2022 cases and closer to sequences from another country, suggesting a new importation as a source. At the start of the resurgence, approximately 16% of first-dose vaccine recipients had completed their second dose.

Conclusions: This investigation demonstrates the importance of ongoing surveillance and preparedness for mpox outbreaks. Undetected local transmission was not a likely source of the 2022-2023 resurgence. Ongoing preexposure vaccine promotion remains important to mitigate disease burden.

Keywords: genomics; mpox; outbreak; surveillance; wastewater.

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Conflict of interest statement

Potential conflicts of interest. D. H. S. T.’s institution has received support for investigator-initiated research from Abbvie and Gilead and for industry-sponsored clinical trials from Glaxo Smith Kline, outside the submitted work. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

Figures

Figure 1.
Figure 1.
Epidemic curve of reported mpox cases in Toronto residents with an overlay of residents receiving vaccine doses administered in the city.
Figure 2.
Figure 2.
Mpox wastewater positivity matrix by collection site (4 sites). Laboratory data are aggregated to the epiweek. The epiweek was regarded as negative if there were no detections across the 3 assays employed in this work (G2R_G, G2R_WA, G2R_NML) for all samples tested that week, where each assay is tested in technical triplicate (9 replicates for each sample). The epiweek was regarded as a weak positive if the average replicate positivity across all assays and samples was ≤11%. The epiweek was regarded as positive if the average replicate positivity was >11% across all assays and samples. If no samples were collected in the corresponding period, the week is regarded as no data.
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