Will Springtime Stop COVID 19?

Everyone is used to speaking of “cold and flu season,” otherwise known as “winter,” and the commonplace supposition is that warm weather and sunshine kills off the common cold rhinovirus. There is some talk of this in relation to COVID 19, naturally, and I stumbled across an interesting paper posted to the Social Science Research Network (SSRN) a few days ago that suggests reasons for thinking COVID 19, like the fictional Andromeda strains from the novel, may thrive in a relative narrow temperature band.

The paper is “Temperature and Latitude Analysis to Predict Potential Spread and Seasonality for COVID-19,” and was written by six public health researchers based mostly at the University of Maryland. The abstract doesn’t tell the whole story of the article, but I start with it anyway:

A significant number of infectious diseases display seasonal patterns in their incidence, including human coronaviruses. We hypothesize that SARS-CoV-2 does as well. To date, Coronavirus Disease 2019 (COVID-19), caused by SARS-CoV-2, has established significant community spread in cities and regions only along a narrow east west distribution roughly along the 30-50 N” corridor at consistently similar weather patterns (5-11 degrees Celsius and low specific and absolute humidity). There has been a lack of significant community establishment in expected locations that are based only on population proximity and extensive population interaction through travel. We have proposed a simplified model that shows a zone at increased risk for COVID-19 spread. Using weather modeling, it may be possible to predict the regions most likely to be at higher risk of significant community spread of COVID-19 in the upcoming weeks, allowing for concentration of public health efforts on surveillance and containment.

This map illustrates the main point with some effect:

The extended discussion at the end of the paper is more detailed and helpful:

The association between temperature in the cities affected with COVID-19 deserves special attention. There is a similarity in the measures of average temperature (5-11 degrees C) and RH (47-79%) in the affected cities and known laboratory conditions that are conducive to coronavirus survival (4 degrees C and 20-80% RH). In the time we have written up these results, new centers of significant community outbreak include parts of Northeastern United States, Spain, Germany, and England, all of which had seen average temperatures between 5-11 degrees C in January and February 2020, and included in either the Jan-Feb 2020 map. . .

In the coming 2 months, temperatures will rise dramatically across many areas in the Northern Hemisphere. However, areas to the north which develop temperature profiles that may now overlap the current areas at risk only transiently as they rapidly warm (with possible exception of areas such as the Northwest United States and British Columbia, which can show prolonged cyclical nadirs). Furthermore, as the virus moves further north it will encounter sequentially less human population densities. The above factors, climate variables not considered or analyzed (cloud cover, maximum temperature, etc.), human factors not considered or analyzed (impact of epidemiologic interventions, concentrated outbreaks like cruise ships, travel, etc.), viral factors not considered or analyzed (mutation rate, pathogenesis, etc.), mean that although the current correlations with latitude and temperature seem strong, a direct causation has not been proven and predictions in the near term are speculative and have to be considered with extreme caution.

Human coronaviruses (HCoV-229E, HCoV-HKU1, HCoV-NL63, and HCoV-OC43), which usually cause common cold symptoms, have been shown to display strong winter seasonality between environmental survival and spreading. . .

All of the above points to a potential direct relation between temperature and SARS-CoV infection. . .

Although it would be even more difficult to make a long-term prediction at this stage, it is tempting to expect COVID-19 to diminish considerably in affected areas (above the 30 degrees N) in the coming months and into the summer.

If I read all of this correctly, it inclines to the view that warmer weather will reduce COVID 19, but we’re really not sure.

More from Science magazine on this aspect of the issue here.

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