ABSTRACT
BACKGROUND: We studied lab-confirmed COVID-19 infection (LCCI) testing, incidence, and severity. METHODS: We included all Manitoba residents and limited our severity analysis to LCCI patients. We calculated testing, incidence and vaccination rates between March 8, 2020 and June 1, 2021. We estimated the association between patient characteristics and testing (rate ratio [RR]; Poisson regression), including the reason for testing (screening, symptomatic, contact/outbreak asymptomatic), incidence (hazard ratio [HR]; Cox regression), and severity (prevalence ratio [PR], Cox regression). FINDINGS: The overall testing rate during the second/third wave was 570/1,000 person-years, with an LCCI rate of 50/1,000 person-years. The secondary attack rate during the second/third wave was 16%. Across regions, young children (<10) had the lowest positivity for symptomatic testing, the highest positivity for asymptomatic testing, and the highest risk of LCCI as asymptomatic contact. People in the lowest income quintile had the highest risk of LCCI, 1.3-6x the hazard of those in the highest income quintile. Long-term care (LTC) residents were particularly affected in the second wave with HRs>10 for asymptomatic residents. INTERPRETATION: Although the severity of LCCI in children was low, they have a high risk of asymptomatic positivity. The groups most vulnerable to LCCI, who should remain a focus of public health, were residents of Manitoba's North, LTC facilities, and low-income neighbourhoods. FUNDING: Canada Research Chair Program.
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 % : 10,518,8). CONCLUSION: La transmission familiale du SRAS-CoV-2 a contribué grandement à l'épidémie locale de la COVID-19.