COVID-19 farm outbreaks in Ontario, January-December 2020

Abstract

Background: Farm workers are critical to Ontario's food supply chain as they grow and harvest the food that Ontario relies on; however, they are subject to several occupation-related coronavirus disease 2019 (COVID-19) transmission risk factors. We describe the epidemiology of farm outbreaks in Ontario over the first calendar year of the pandemic and explore trends in outbreaks by season and type of farm.

Methods: Data pertaining to farm outbreaks in Ontario from January 1 to December 31, 2020, and their associated laboratory-confirmed cases were extracted from the provincial database. Outbreaks were characterized by size, season, farm type and duration. Cases were characterized by age, gender, medical risk factors, clinical presentation and outcomes.

Results: There were 64 farm outbreaks associated with 2,202 confirmed cases of COVID-19 in Ontario during 2020. The majority of outbreaks occurred in spring (n=25, 39.1%) and fall (n=25, 39.1%). The fewest outbreaks occurred in the summer (n=6, 9.4%), corresponding with low community rates during that time, and the majority of these were in greenhouse farms (n=5, 83.3%). The median outbreak size was 14.5 cases (range: 1-240), and the median duration was 23 days (range: 0-128). Among cases, most were male (83.2%), the median age was 35 years, 10.0% had one or more comorbidities, 31.2% were asymptomatic, 16 required hospitalization and three died.

Conclusion: Farm outbreaks were a source of COVID-19 transmission and illness in 2020, particularly in the spring and fall. Outbreaks continued in greenhouse farms despite lower summer community transmission.

Keywords: COVID-19; farm; outbreaks; workers; workplace.

Figure 1

Epidemiologic curve of COVID-19 farm outbreaks in Ontario, January 1–December 31, 2020^a Abbreviations: COVID-19, coronavirus disease 2019; PHU, public health unit ^a Bars correspond to the number of outbreaks reported by the top three PHUs with the most COVID-19 on-farm outbreaks reported in Ontario and the total number of COVID-19 on-farm outbreaks reported by all other PHUs combined. The black line corresponds to total number of COVID-19 on-farm cases reported across all PHUs in Ontario. Top 3 PHUs correspond to PHUs with most outbreaks reported in the province: Windsor-Essex county Health Unit (N=35), Haldimand-Norfolk Health Unit (N=6) and Chatham-Kent Public Health (N=4)