Fast spread of COVID-19 in Europe and the US and its implications: even modest public health goals require comprehensive intervention

Ruian Ke, PhD, Steven Sanche, PhD, Ethan Romero-Severson, PhD, Nick Hengartner, PhD

medRxiv, doi: https://www.medrxiv.org/content/10.1101/2020.04.04.20050427v1.full.pdf

Findings: In all countries, the  early epidemic period was characterized by exponential growth with rates between 0.19-.29/day (epidemic doubling times between 2.4-3.7 days). However, the proportion of cases that had been detected was low ... With such high epidemic growth rates, moderate intervention efforts will have little impact on the public health outcome; high levels of efforts to achieve greater than 77-86<% reduction in transmission are needed, no matter whether the goal is to slow down the growth to protect a large fraction of population from infection within 18 months, or to reverse the growth all together.

Interpretation:  The extremely fast spread of COVID-19 in Europe and the US suggest a highly infectious virus with a high R0. Early, strong  and comprehensive intervention efforts are necessary, whether the aim is mitigation or containment.

High Contagiousness and Rapid Spread of Severe Acute Respiratory Syndrome Coronavirus 2

Steven Sanche, Yen Ting Lin, Chonggang Xu, Ethan Romero-Severson, Nick Hengartner, Ruian Ke

EID Journal: https://wwwnc.cdc.gov/eid/article/26/7/20-0282_article

Severe acute respiratory syndrome coronavirus 2 is the causative agent of the 2019 novel coronavirus disease pandemic. Initial estimates of the early dynamics of the outbreak in Wuhan, China, suggested a doubling time of the number of infected persons of 6–7 days and a basic reproductive number (R0) of 2.2–2.7. We collected extensive individual case reports across China and estimated key epidemiologic parameters, including the incubation period. We then designed 2 mathematical modeling approaches to infer the outbreak dynamics in Wuhan by using high-resolution domestic travel and infection data. Results show that the doubling time early in the epidemic in Wuhan was 2.3–3.3 days. Assuming a serial interval of 6–9 days, we calculated a median R0 value of 5.7 (95% CI 3.8–8.9). We further show that active surveillance, contact tracing, quarantine, and early strong social distancing efforts are needed to stop transmission of the virus.

Emergence of SARS-CoV-2 through Recombination and Strong Purifying Selection

Xiaojun Li, Elena E. Giorgi, Manukumar Honnayakanahalli Marichann, Brian Foley, Chuan Xiao, Xiang-peng Kong, Yue Chen, Bette Korber, Feng Gao

bioRxiv, doi: https://doi.org/10.1101/2020.03.20.000885

Our team demonstrated, by looking at the genetic sequence of the virus and comparing it to other known coronaviruses, that it originated from animals. More specifically, it most likely came from a family of bat viruses that acquired the ability to infect human cells from another family of coronaviruses found in pangolins.

School dismissal as a pandemic influenza response: When, where and for how long

Timothy C. Germann, Hongjiang Gao, Manoj Gambhir, Andrew Plummer, Matthew Biggerstaff, Carrie Reed, Amra Uzicanin

Epidemics, 2019 – Elsevier

We used individual-based computer simulation models at community, regional and national levels to evaluate the likely impact of coordinated pre-emptive school dismissal policies during an influenza pandemic. Such policies involve three key decisions: when, over what geographical scale, and how long to keep schools closed. Our evaluation includes uncertainty and sensitivity analyses, as well as model output uncertainties arising from variability in serial intervals and presumed modifications of social contacts during school dismissal periods.