is COVID-19 seasonal

Researchers investigate the potential spread of COVID-19 in relation to temperature, humidity, and latitude analysis. 

COVID-19 has caused a global pandemic resulting in over 400,000 deaths worldwide at present. Human coronaviruses often display seasonal patterns in their occurrence, and several previous studies point to the role of ambient temperature and humidity in the spread of respiratory viruses. In the hope to aid preventative and surveillance strategies, researchers from the University Of Maryland School Of Medicine in Baltimore designed a cohort study to examine the association of climate, with the spread of COVID-19. 

Published in JAMA Network Open, the study examined data from fifty cities with and without community spread of COVID-19. Eight cities considered to have substantial community spread (Wuhan, Tokyo, Daegu, Qom, Milan, Paris, Seattle, and Madrid) were compared with 42 cities that had not seen substantial community spread. Data were collected between January and March 10, 2020, defining community transmission as at least ten reported deaths in a country. 

Results from the study show that substantial community spread occurred inside a narrow band of latitude. The eight cities listed above are all located between 30˚N – 50˚N and have similar weather patterns. During this period, they had mean temperatures of 5-11˚C and low humidity. During the same period, COVID-19 failed to have the same level of community spread immediately north or south of this band of latitude. For example, the reported number of cases and deaths are much lower in both Moscow (56˚N) and Hanoi (21.2˚N). The distribution of significant community spread was consistent with the behaviour of a seasonal respiratory virus. 

Temperature and humidity are known to influence coronavirus survival. The affected cities had similar conditions proven conducive to coronavirus survival in a laboratory. In comparison, colder areas in more northern latitudes have been impacted much less by COVID-19. Coronaviruses are also seen to have strong winter seasonality and become less prevalent in hotter summer months. With this in mind, this study points to the suggestion that COVID-19 will diminish considerably (in the affected areas above 30˚N) in the summer. 

This study looked purely at temperature, humidity, and latitude in relation to the spread of COVID-19. Therefore other factors such as travel, population density, pollution, and public health interventions were not considered. However, developing a better understanding of the association of climate, with the spread of COVID-19, could determine which areas need higher surveillance. This type of weather modelling could be used to estimate which areas are at higher risk of COVID-19 over the coming months.

Written by Helen Massy, BSc.

References:

Sajadi, M., Habibzadeh, P., Vintzileos, A., Shokouhi, S., Miralles-Wilhelm, F. and Amoroso, A., 2020. Temperature, Humidity, and Latitude Analysis to Estimate Potential Spread and Seasonality of Coronavirus Disease 2019 (COVID-19). JAMA Network Open, 3(6), p.e2011834.

EurekAlert!. 2020. Temperature, Humidity, Latitude Analysis To Estimate Potential Spread, Seasonality Of COVID-19. [online] Available at: <https://www.eurekalert.org/pub_releases/2020-06/jn-thl061020.php> [Accessed 16 June 2020].

Image by NickyPe from Pixabay 

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