Estimating key parameters for SARS-CoV-2 outbreaks and implications for control
Two epidemiological parameters that are of paramount importance in assessing the epidemic potential of a novel pathogen are the early epidemic growth rate and the basic reproductive number, R0. Yet their values for the SARS-CoV-2 outbreak in Wuhan were highly debated in early 2020 and this led to vast different assessments of the potential of SARS-CoV-2 to cause global pandemic. In this talk, I will present our efforts to estimate these two parameter values and how we reached the conclusion in early Feb. 2020 that early, strong social distancing efforts are necessary to stop the spread of the virus. This is in stark contrast to the prevalent view at that time that SARS-CoV-2 does not pose a high risk of global pandemic. More specifically, we estimated that the early epidemic grew exponentially at rates between 0.19-0.29/day (epidemic doubling times between 2.4-3.7 days) and the reproductive numbers are likely between 3.9 and 7.1. This translates to high herd immunity thresholds to reach to stop SARS-CoV-2 transmission. We further estimated similar epidemic growth rates and the basic reproductive numbers for SARS-CoV-2 outbreaks in Europe and the US. If time permits, I will also talk about our collaborative work on analyzing data from Ecuador (where the highest per capita excess deaths were reported) and highlight the potential devastating consequence of wide-spread COVID-19 in a developing country.