The first three months of the COVID-19 epidemic: Epidemiological evidence for two separate strains of SARS-CoV-2 viruses spreading and implications for prevention strategies

Knut M. Wittkowski

In NY, one of the epicenters of the U.S. epidemic, "social distancing" started about 03-15 with closure of schools being announced and 03-17 with restaurants being closed, and intensified on 03-22 with the closure of all non-essential businesses (similar actions were taken in New Jersey and Connecticut). Given the fast rise in number of cases in NYC turning on 03-22 (Fig 10c) , which was also observed in Detroit, Chicago, and Dallas, see [https://www.nytimes.com/interactive/2020/03/27/upshot/coronavirus-new-york-comparison.html , accessed 04-03] ), an intervention at 03-22 started at the turning point (Fig 13) . Hence the virus will spread in the population much longer with "social distancing", and a reduction of deaths through the intervention is possible (albeit not guaranteed). A turning point of 03-22 in NYC is consistent with a projected peak (Murray 2020) of 524-1,090 deaths on 04-10 ( http://www.healthdata.org/covid/updates , accessed on 2020-04-04) compared to the average of 246.5 on 04-02/03. In California, a shutdown was ordered on 03-19 (Executive order N-33-20) and many states and cities in the US followed suit, mandating schools, restaurants, and "non-essential" businesses. The turning point in the In the U.S. as a whole, however, cannot have been earlier than 03-27 (Fig 10) . Hence, social distancing was ordered before the epidemic reached its turning point, and a "flattened", but much broader with the virus staying in the population until the intervention is changed (or ignored) so that herd immunity can be reached.