Virus World

This paper investigates how air temperature and humidity influence the transmission of COVID-19. After estimating the serial interval of COVID-19 from 105 pairs of the virus carrier and the infected, we calculate the daily effective reproductive number, R, for each of all 100 Chinese cities with more than 40 cases. Using the daily R values from January 21 to 23, 2020 as proxies of non-intervened transmission intensity, we find, under a linear regression framework for 100 Chinese cities, high temperature and high relative humidity significantly reduce the transmission of COVID-19, respectively, even after controlling for population density and GDP per capita of cities. One degree Celsius increase in temperature and one percent increase in relative humidity lower R by 0.0383 and 0.0224, respectively.

This result is consistent with the fact that the high temperature and high humidity significantly reduce the transmission of influenza. It indicates that the arrival of summer and rainy season in the northern hemisphere can effectively reduce the transmission of the COVID-19.

Published on arXIV (March 9, 2020):

https://arxiv.org/ftp/arxiv/papers/2003/2003.05003.pdf

The coronavirus that causes COVID-19, SARS-CoV-2, can survive for several hours in an aerosolized form and for up to three days on plastic and steel surfaces, researchers reported Tuesday (March 10) on medRxiv. While the detection of viable virus means it’s theoretically possible to transmit the disease from contaminated surfaces or from the air—in addition to the typical route of having larger droplets land directly on a new host after an infected person, say, coughs in their proximity—“We’re not by any way saying there is aerosolized transmission of the virus,” coauthor Neeltje van Doremalen of the National Institute of Allergy and Infectious Diseases tells the Associated Press.

The authors applied SARS-CoV-2 and SARS-CoV, the virus that caused the SARS outbreak of 2003, to plastic, stainless steel, copper, and cardboard in the lab and created aerosolized viruses using a nebulizer. They found viable SARS-CoV-2 three hours after the virus was aerosolized and suspended in the air within a drum, and on surfaces four hours, 24 hours, and 2–3 days after it was deposited to copper, cardboard, and steel or plastic, respectively. SARS-CoV lasted about as long, although it lost viability sooner on cardboard and more slowly on copper. The median half-life for SARS-CoV-2 was 13 hours on steel and 16 hours on plastic. “It’s a solid piece of work that answers questions people have been asking,” Julie Fischer, a microbiologist at Georgetown University who was not involved in the study, tells the AP. “What we need to be doing is washing our hands, being aware that people who are infected may be contaminating surfaces,” and not touching our faces....

Published in medRxiv (March 13, 2020):

https://doi.org/10.1101/2020.03.09.20033217