Fighting a Fire versus Waiting for the Wave: Useful and Not-So-Useful Analogies in Times of SARS-CoV-2

As SARS-CoV-2 has swept the planet, intermittent lockdowns have become a regular feature to control transmission. References to so-called recurring waves of infections remain pervasive among news headlines, political messaging, and public health sources. We explore the power of analogies to facilitate understanding of biological models and processes by reviewing strengths and limitations of analogies used throughout the COVID-19 pandemic. We consider how, when analogies fall short, their ability to persuade can mislead public perception, even if unintentionally. Although waves can convey patterns of disease outbreak, we suggest process-based analogies might be more effective communication tools, given that they can be easily mapped to underlying epidemiological concepts and extended to include complex dynamics. Although no single analogy perfectly captures disease dynamics, fire is particularly suitable for visualizing epidemiological models, underscoring the importance and reasoning behind control strategies and potentially conveying a sense of urgency that can galvanize individual and collective action.

Establishment, contagiousness, and initial spread of SARS-CoV-2 in Canada

This study empirically quantifies dynamics of SARS-CoV-2 establishment and early spread in Canada. We developed a transmission model that was simulation tested and fitted in a Bayesian framework to timeseries of new cases per day prior to physical distancing interventions. A hierarchical version was fitted to all provinces simultaneously to obtain average estimates for Canada. Across scenarios of a latent period of 2-4 d and an infectious period of 5-9 d, the R-0 estimate for Canada ranges from a minimum of 3.0 (95% CI: 2.3-3.9) to a maximum of 5.3 (95% CI: 3.9-7.1). Among provinces, the estimated commencement of community transmission ranged from 3 d before to 50 d after the first reported case and from 2 to 25 d before the first reports of community transmission. Among parameter scenarios and provinces, the median reduction in transmission needed to obtain R-0 < 1 ranged from 46% (95% CI: 43%-48%) to 89% (95% CI: 88%-90%). Our results indicate that local epidemics of SARS-CoV-2 in Canada entail high levels of stochasticity, contagiousness, and observation delay, which facilitates rapid undetected spread and requires comprehensive testing and contact tracing for its containment.