ABSTRACT
OBJECTIVE: To characterize SARS-CoV-2 transmission following a COVID-19 outbreak in an emergency childcare centre (ECCC) in April 2020 in Quebec, Canada. METHODS: The study population consisted of all the children and employees who attended the ECCC as well as household contacts of the confirmed COVID-19 cases. Of the 120 individuals in the study, five cases were confirmed by epidemiological link and 25 were identified as COVID-19 by RT-PCR among which 19 were analyzed by viral whole genome sequencing. Descriptive epidemiology, social network visualization, and phylogenetic analysis were used to characterize viral transmission. RESULTS: Phylogenetic analysis identified two separate introductions of distinct lineages of SARS-CoV-2 and estimated an average effective reproductive number of Re = 1.9 (range 0.9-4.9) with a mean doubling time of 3.2 days (range 2.1-5.2). The first and most prevalent lineage was introduced by two asymptomatic children who were likely infected by their parent, a confirmed COVID-19 case working in a long-term care centre. Among infected household adults, attack rates were significantly higher in mothers than in fathers (risk ratio = 4.5; 95% CI 1.1-18.7). The extent of transmission makes it one of the largest documented outbreaks in a daycare in Canada. CONCLUSION: The analyses carried out showed the probable origin and direction of the transmission of the infection (adult-child, child-adult, and child-child), thus highlighting how asymptomatic children can efficiently transmit SARS-CoV-2.
RéSUMé: OBJECTIF: Caractériser la transmission du SRAS-CoV-2 à la suite d'une éclosion de COVID-19 dans un service de garde d'urgence en milieu scolaire (SGUMS) en avril 2020 au Québec, Canada. MéTHODES: La population à l'étude était composée de tous les enfants et employés ayant fréquenté le SGUMS ainsi que les contacts familiaux des cas confirmés de COVID-19. Sur les 120 personnes à l'étude, cinq cas ont été confirmés par lien épidémiologique et 25 par RT-PCR. Parmi ces derniers, 19 ont été analysés par séquençage viral du génome entier. La caractérisation de la transmission a été réalisée à l'aide d'analyses descriptives et phylogénétiques ainsi que de la visualisation de réseaux sociaux. RéSULTATS: L'analyse phylogénétique a identifié deux introductions de lignées distinctes du SRAS-CoV-2 et un taux de reproduction net Re = 1,9 (étendue 0,94,9) avec un temps moyen de doublement de 3,2 jours (étendue 2,15,2). La première lignée, et la plus répandue, a été introduite par deux enfants asymptomatiques qui ont probablement été infectés par leur parent, un travailleur de la santé atteint de COVID-19. Dans les noyaux familiaux, les taux d'attaque étaient significativement plus élevés chez les mères que chez les pères (rapport de risque = 4,5 ; IC à 95 % 1,118,7). L'ampleur de la transmission en fait de celle-ci la plus importante éclosion documentée dans un service de garde au Canada. CONCLUSION: Cette étude a permis de déterminer l'origine et la direction probables de la transmission de l'infection (adulte-enfant, enfant-adulte et enfant-enfant) et démontrer que les enfants asymptomatiques peuvent transmettre le SRAS-CoV-2.
Subject(s)
COVID-19/epidemiology , COVID-19/transmission , Child Day Care Centers , Disease Outbreaks , Adolescent , Adult , Aged , Child , Child, Preschool , Contact Tracing , Emergencies , Female , Humans , Male , Middle Aged , Phylogeny , Quebec/epidemiology , SARS-CoV-2/genetics , SARS-CoV-2/isolation & purification , Young AdultABSTRACT
OBJECTIVES: The objective of this study is to describe an important waterborne outbreak of gastrointestinal illness observed in a rural municipality of Quebec. METHODS: A population-based retrospective cohort study was conducted to identify risk factors associated with acute gastroenteritis. Indirect surveillance data were used to estimate the extent and the resolution of the epidemic. RESULTS: The cohort consisted of 140 randomly selected individuals of whom 22 met the illness case definition (15.7% attack rate). The epidemic curve was similar to the evolution of antidiarrheal products sold by the only pharmacy in town and calls made to the Health Info Line. Bivariate analysis led to identifying five risk factors of gastrointestinal illness: consumption of municipal water, contact with someone with acute gastroenteritis (within and outside of the household), contact with a child in daycare, and being less than 35 years of age. Drinking municipal water had the highest risk ratio (RR = 24.31; 95% CI = 1.50-393.4). Drinking water from a private artesian well was a protective factor (RR = 0.28; 95% CI = 0.09-0.90). CONCLUSION: This study highlighted that managing the risks associated with the consumption of untreated drinking water remains an important public health challenge, particularly in small rural municipalities vulnerable to climate variability.
