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

Abstract

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. SARS-CoV-2. Secondary attack rates. Household transmission. Emerging infectious diseases Mots-clés COVID-19. SRAS-CoV-2. taux d'infection secondaire. transmission familiale. maladies infectieuses émergentes

SARS-CoV-2 Quantitative Real Time PCR and Viral Loads Analysis Among Asymptomatic and Symptomatic Patients: an Observational Study on an Outbreak in Two Nursing Facilities in Campania Region (Southern Italy)

“…Moreover, Pujadas and colleagues showed that high viral load was correlated to higher mortality rates, suggesting to use quantitative analyses for patient risk-strati cation [10], thus, high viral load could act a key role in the severity of COVID-19. These ndings were supported by other studies reporting an association between high viral loads and more severe symptoms [6][7][8][9][10][11]17]. Otherwise, other studies did not show any statistically signi cant difference in viral loads between symptomatic and asymptomatic individuals [10][11][12][13][14][15][16][17][18]20], while Hasanoglu and colleagues showed that higher viral loads were found in asymptomatic patients when compared to symptomatic ones and that, the more the clinical course of the diseases was severe, the lower viral loads were observed, together with a signi cant negative trend with increasing age [5].…”

“…The disease clinical course is characterized by several factors, from asymptomatic to mild or severe viral respiratory tract infections, up to systemic in ammation and thrombosis [5]. Several other risk factors have also been identi ed to affect the disease course, such as gender, concomitant diseases, close contact and age [5,8]. Indeed, Centers for Disease Control and Prevention (CDC) has identi ed 65 years old and older people at a greater risk of hospitalization and death for COVID-19, from 90x higher risk of death for 65-74 years old, up to 630x higher for over 85 years old people [9].…”

Factors Associated With Household Transmission of SARS-CoV-2

“…Compared with the SAR for 28 studies 12,14,17,27,94 from January to February 2020 (13.4%; 95% CI, 10.7%-16.7%), the SAR was significantly higher for 30 studies 6,7,15,16,19,22,25,26,28,30,[68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86]93 from March to April 2020 (19.4%; 95% CI, 15.2%-24.5%; P = .03) and 15 studies 5,8,10,18,20,21,23,24,29,31,32,35,37,38,40 from July 2020 to March 2021 (31.1%; 95% CI, 22.6%-41.1%; P < .001) but not significantly different from the SAR for 14 studies…”

“…Characteristics of Studies Included in Analysis of Household Secondary Attack Rates for SARS-CoV-2 (continued) ,23,24,29,37,40,45,79,[88][89][90]92 21.0(13.8-30.6) No 75[4][5][6][7][9][10][11][12][13][14][15][16][17][18][19][20][21][22][25][26][27][28][30][31][32][33][34][35][36][37][38][39][74][75][76][77][78][80][81][82][83][84]…”

Incidence, household transmission, and neutralizing antibody seroprevalence of Coronavirus Disease 2019 in Egypt: Results of a community-based cohort

“…In the USA, secondary attack rates were estimated between 0.5-53% [15,16,18,19]. In Canada, a 14.7% secondary infection rate was calculated [20]. A meta-analysis estimated the rate to be around 17% [21].…”