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 Italy (Fig 6) , incidence has been declining from the 100/M/d peak for over two weeks over two weeks, after rising for about 4 weeks from 1/M (02-26..~03-22). In Hubei and South Korea, instead incidence took only 2 weeks to peak (01-19..02-05, Fig 4, and 02-21..03-06, Fig 5) and then declined by at least 85% within another 2 weeks. The much slower decline in Italy (compared, e.g., to China and Hubei) is consistent with insufficient herd immunity having been developed before the peak incidence was reached (Fig 3) . While Italy and its neighbors (Europe/high) peaked in 03-27/28 (Fig 7) . On 04-04, France added previously unreported cases from nursing homes, which let to reporting irregularities. Overall, the incidence in Europe reached its peak on 03-28 in the countries with high lethality and on 04-04 in the other countries.