A warming light at the end of the COVID-19 tunnel?
March 13, 2020
A study released March 9 provides some comfort to a panicked world over the continued possible spread of the COVID-19 virus and predicts limiting factors that may impede further contagion. The report, Temperature and Latitude Analysis to Predict Potential Spread and Seasonality for COVID-19 was an in-depth review linking warming temperatures to declining infections in China and elsewhere. The research team included six experts from prestigious universities and laboratories including the Institute of Human Virology and the Global Virus Network.
any infectious diseases display seasonality in their occurrence and this report predicts that the Coronavirus Disease 2019 (COVID-19), caused by SARS-CoV-2, will follow this pattern with declining incidence coinciding with warming temperatures in the northern hemisphere. According to the report, “The marked drop in cases in Wuhan could well be linked to corresponding recent rising temperatures there.”
Even more encouraging was their statement concerning the family of coronaviruses that “have been shown to display strong winter seasonality between December and April and are undetectable in summer months in temperate regions.” This is certainly welcome news to worried citizens around the world if, indeed, the warming that is already occurring as the northern hemisphere heads into spring and summer can alleviate further outbreaks.
The authors also stated “Notably, during the same time, COVID-19 failed to spread significantly to countries immediately south of China. The number of patients and reported deaths in Southeast Asia is much less when compared to more temperate regions noted above.”
While the above news is extremely helpful and informative, the most fascinating and ground-breaking portion of the study was their contention that the hot spots of infection as of March 5, 2020, were located within a narrow band of temperature and humidity. The authors state that the virus 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 (5-11OC and 47-79% humidity).”
The team had initially created a map of possible future areas of likely contamination (Figure 1) that included Korea, Japan, Iran and northern Italy. The recent new outbreak areas in France and the northwest United States have since been added and fell neatly into the areas predicted for additional risk.
Figure 1 – Sajadi et al 2020
The team noted that the outbreak areas had similar temperature, humidity, and latitude. In addition, the timing of the initial outbreaks coincided with the coldest portions of the year and none of the areas experienced minimum temperatures below freezing. The temperatures and humidity of the affected areas were reported to be similar to laboratory testing of conditions that are conducive to the survival of the coronavirus. Survival of the SARS-CoV and MERS-Cov were also determined to be limited by temperature and humidity.
The prediction of declining mortality with warming temperature is supported by numerous studies showing that cold is much more deadly than heat. According to a study of temperature-related deaths in the U. K. and Australia, cold kills more than 15 times as many people in these countries as heat. In the largest study to date on deaths attributable to heat or cold, a large team of physicians from around the world examined more than 74 million deaths in 13 countries between 1985 and 2012. The study revealed that cold weather kills 20 times as many people as heat (Figure 2).
Figure 2 – Gasparrini et al 2015
What does this all mean? It is possible that the COVID-19 virus will be restricted somewhat by rising temperatures in areas already affected but with warming temperatures, the “at risk” areas will spread northward. For the most part, these areas are more sparsely populated and temperatures at this time of year tend to increase quickly.
It certainly appears that the timing of this outbreak was fortunate in that its spread worldwide is occurring while the northern hemisphere is warming. We will likely know soon if that light at the end of the tunnel is the welcome warming of spring and summer that will bring on a respite from the contagion or an oncoming train. I doubt that there is a middle ground.
Gasparrini A, et al., Mortality risk attributable to high and low am-bient temperature: a multicountry observational study, The Lancet, Vol 386 July 25, 2015
Sajadi, M.M., et al., Temperature and Latitude Analysis to Predict Potential Spread and Seasonality for COVID-19 (March 5, 2020). Available at SSRN: https://ssrn.com/abstract=3550308 or http://dx.doi.org/10.2139/ssrn.3550308