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. 2023 Jan;176(1):67-76.
doi: 10.7326/M22-2699. Epub 2022 Dec 13.

Monkeypox in Montréal: Epidemiology, Phylogenomics, and Public Health Response to a Large North American Outbreak

Luke B Harrison  1 , Geneviève Bergeron  2 , Geneviève Cadieux  3 , Hugues Charest  4 , Judith Fafard  4 , Inès Levade  5 , Antoine Cloutier Blais  6 , Emmanuelle Huchet  6 , Benoît Trottier  7 , Dragos Vlad  7 , Jason Szabo  8 , Réjean Thomas  8 , Sébastien Poulin  9 , Christina Greenaway  10 , Gerasimos J Zaharatos  11 , Matthew Oughton  11 , Arpita Chakravarti  12 , Robert Pilarski  13 , Andrew Bui-Nguyen  14 , Khadija Benomar  14 , Michael D Libman  15 , Donald C Vinh  16 , Ana T Duggan  17 , Morag Graham  18 , Marina B Klein  19 , Sapha Barkati  15
Affiliations
Free article

Monkeypox in Montréal: Epidemiology, Phylogenomics, and Public Health Response to a Large North American Outbreak

Luke B Harrison et al. Ann Intern Med. 2023 Jan.
Free article

Abstract

Background: Monkeypox, a viral zoonotic disease, is causing a global outbreak outside of endemic areas.

Objective: To characterize the outbreak of monkeypox in Montréal, the first large outbreak in North America.

Design: Epidemiologic and laboratory surveillance data and a phylogenomic analysis were used to describe and place the outbreak in a global context.

Setting: Montréal, Canada.

Patients: Probable or confirmed cases of monkeypox.

Measurements: Epidemiologic, clinical, and demographic data were aggregated. Whole-genome sequencing and phylogenetic analysis were performed for a set of outbreak sequences. The public health response and its evolution are described.

Results: Up to 18 October 2022, a total of 402 cases of monkeypox were reported mostly among men who have sex with men (MSM), most of which were suspected to be acquired through sexual contact. All monkeypox genomes nested within the B.1 lineage. Montréal Public Health worked closely with the affected communities to control the outbreak, becoming the first jurisdiction to offer 1 dose of the Modified Vaccinia Ankara-Bavarian Nordic vaccine as preexposure prophylaxis (PrEP) to those at risk in early June 2022. Two peaks of cases were seen in early June and July (43 and 44 cases per week, respectively) followed by a decline toward near resolution of the outbreak in October. Reasons for the biphasic peak are not fully elucidated but may represent the tempo of vaccination and/or several factors related to transmission dynamics and case ascertainment.

Limitations: Clinical data are self-reported. Limited divergence among sequences limited genomic epidemiologic conclusions.

Conclusion: A large outbreak of monkeypox occurred in Montréal, primarily among MSM. Successful control of the outbreak rested on early and sustained engagement with the affected communities and rapid offer of PrEP vaccination to at-risk persons.

Primary funding source: None.

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