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. 2022 May 3:10:867425.
doi: 10.3389/fpubh.2022.867425. eCollection 2022.

Social Contacts and Transmission of COVID-19 in British Columbia, Canada

Notice Ringa  1   2 , Sarafa A Iyaniwura  1   3 , Samara David  1 , Mike A Irvine  1   4 , Prince Adu  1   2 , Michelle Spencer  1 , Naveed Z Janjua  1   2 , Michael C Otterstatter  1   2
Affiliations

Social Contacts and Transmission of COVID-19 in British Columbia, Canada

Notice Ringa et al. Front Public Health. .

Abstract

Background: Close-contact rates are thought to be a driving force behind the transmission of many infectious respiratory diseases. Yet, contact rates and their relation to transmission and the impact of control measures, are seldom quantified. We quantify the response of contact rates, reported cases and transmission of COVID-19, to public health contact-restriction orders, and examine the associations among these three variables in the province of British Columbia, Canada.

Methods: We derived time series data for contact rates, daily cases and transmission of COVID-19 from a social contacts survey, reported case counts and by fitting a transmission model to reported cases, respectively. We used segmented regression to investigate impacts of public health orders; Pearson correlation to determine associations between contact rates and transmission; and vector autoregressive modeling to quantify lagged associations between contacts rates, daily cases, and transmission.

Results: Declines in contact rates and transmission occurred concurrently with the announcement of public health orders, whereas declines in cases showed a reporting delay of about 2 weeks. Contact rates were a significant driver of COVID-19 and explained roughly 19 and 20% of the variation in new cases and transmission, respectively. Interestingly, increases in COVID-19 transmission and cases were followed by reduced contact rates: overall, daily cases explained about 10% of the variation in subsequent contact rates.

Conclusion: We showed that close-contact rates were a significant time-series driver of transmission and ultimately of reported cases of COVID-19 in British Columbia, Canada and that they varied in response to public health orders. Our results also suggest possible behavioral feedback, by which increased reported cases lead to reduced subsequent contact rates. Our findings help to explain and validate the commonly assumed, but rarely measured, response of close contact rates to public health guidelines and their impact on the dynamics of infectious diseases.

Keywords: COVID-19; correlation; regression; social contacts; transmission control.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Time series of average daily contacts (contact rates), average daily cases (new cases) and transmission (Rt) of COVID-19 in BC (A,D,G), FHA (B,E,H) and VCHA (C,F,I) from September 13, 2020 to February 19, 2021. The vertical dotted lines indicate dates of announcement of public health contact-restriction orders on October 26, 2020, November 07, 2020 and November 19, 2020. Each plot contains derived segmented linear regression lines with three knots at the dates of introduction of the public health orders. Horizontal lines in the plots for transmission indicate the transmission threshold Rt = 1.
Figure 2
Figure 2
Forecast error variance decomposition (FEVD) results for VAR models of average daily contacts and cases and average daily contacts and transmission in BC (A,B), FHA (C,D), and VCHA (E,F).
See this image and copyright information in PMC

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