Timing the SARS-CoV-2 index case in Hubei Province

Understanding when SARS-CoV-2 emerged is critical to evaluating our
current approach to monitoring novel zoonotic pathogens and understanding
the failure of early containment and mitigation efforts for COVID-19. We
employed a coalescent framework to combine retrospective molecular clock
inference with forward epidemiological simulations to determine how long
SARS-CoV-2 could have circulated prior to the time of the most recent
common ancestor. Our results define the period between mid-October and
mid-November 2019 as the plausible interval when the first case of
SARS-CoV-2 emerged in Hubei province. By characterizing the likely
dynamics of the virus before it was discovered, we show that over
two-thirds of SARS-CoV-2-like zoonotic events would be self-limited, dying
out without igniting a pandemic. Our findings highlight the shortcomings
of zoonosis surveillance approaches for detecting highly contagious
pathogens with moderate mortality rates.