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. 2021 Feb;112(1):12-16.
doi: 10.17269/s41997-020-00451-x. Epub 2020 Nov 17.

Secondary attack rate of COVID-19 in household contacts in the Winnipeg Health Region, Canada

Krista Wilkinson  1 , Xuan Chen  2 , Souradet Shaw  2
Affiliations

Secondary attack rate of COVID-19 in household contacts in the Winnipeg Health Region, Canada

Krista Wilkinson et al. Can J Public Health. 2021 Feb.

Abstract
in English, French

Objectives: Understanding important transmission parameters, such as secondary attack rates, can help in strategizing, prioritizing, and planning interventions to curb morbidity and mortality due to COVID-19. Early reports suggest the risk of transmission of SARS-CoV-2 (the pathogen that causes COVID-19 disease) is high among household contacts of cases. The purpose of this analysis was to determine the household transmissibility of SARS-CoV-2 in residents of the Winnipeg Health Region.

Methods: We extracted information on COVID-19 cases and their household contacts from the regional public health surveillance database and used this dataset to calculate secondary attack rates.

Results: We included 381 individuals from 102 unique households (102 primary cases and 279 household contacts). A total of 41 contacts from 25 households became secondary cases in the 14 days since last unprotected exposure to the primary case, resulting in a secondary attack rate of 14.7% (95% CI: 10.5-18.8).

Conclusion: Household transmission of SARS-CoV-2 has been an important contributor to the local COVID-19 epidemic.

RéSUMé: OBJECTIFS: Comprendre les importants paramètres de transmission, comme les taux d’infection secondaire, peut aider à établir des stratégies et des priorités et à planifier des interventions afin de réduire la morbidité et la mortalité liées à la COVID-19. Les premiers rapports laissent entendre que le risque de transmission du SRAS-CoV-2 (l’agent pathogène qui cause la COVID-19) est élevé parmi les contacts familiaux de cas de COVID-19. Le but de cette analyse visait à déterminer la transmissibilité familiale du SRAS-CoV-2 chez les résidents de la région sanitaire de Winnipeg. MéTHODES: Nous avons tiré l’information sur les cas de COVID-19 et de leurs contacts familiaux de la base de données de surveillance de la santé publique à l’échelle régionale et nous avons utilisé ces données pour calculer les taux d’infection secondaire. RéSULTATS: Nous avons inclus 381 personnes de 102 ménages uniques (102 cas primaires et 279 contacts familiaux). Au total, 41 contacts de 25 ménages sont devenus des cas secondaires dans les 14 jours depuis la dernière exposition non protégée au cas primaire, ce qui correspond à un taux d’infection secondaire de 14,7 % (IC de 95 % : 10,5–18,8). CONCLUSION: La transmission familiale du SRAS-CoV-2 a contribué grandement à l’épidémie locale de la COVID-19.

Keywords: COVID-19; Emerging infectious diseases; Household transmission; SARS-CoV-2; Secondary attack rates.

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Conflict of interest statement

The authors declare that they have no conflict of interest.

Figures

Fig. 1
Fig. 1
Social network diagram of households with COVID-19 cases in the Winnipeg Health Region; green dots represent primary cases, red dots represent secondary cases, and yellow dots represent asymptomatic household contacts; lines connect case(s) to named household contacts
See this image and copyright information in PMC

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