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Pandemics don’t behave like seasonal outbreaks

By Dr Hasnain Javed
April 01, 2020

Many infectious diseases like seasonal flu, typhoid and measles have great adaptability with temperature variations. But the infectious agent of COVID-19 that is SARS-COV-2 is relatively new and very limited information is available about its transmission and spread with variation of temperature and humidity.

The closet relative of this virus is the one that caused the SARS in 2003 and information about viral structure and its spread are basically based on data available for SARS virus. This virus was, fortunately, contained very quickly and limited information is available about its spread associated with temperature and humidity. The coronavirus pandemic has sickened more than 465,100 people yet according to recent available data. As of Thursday morning, at least 20,977 people have died, and the virus has been detected in more than 171 countries with sustained transmission of virus in six continents.

Some recent data (both published and unpublished) reveal that there is a relation of SARS-COV-2 spread with temperature, speed of wind and relative humidity. The studies are based on initial spread of virus in mid-December suggesting its transmission in cold environment. Another study revealed the relative decrease in COV-2 with every 1oC increase in temperature. These studies were based on the country and region wise data obtained for new cases and temperature of the region. A recent study revealed that high temperature and high relative humidity significantly reduce the spread of COVID-19. A sharp spread of COVID-19 in a very short time in both the areas of low and high temperatures suggests that this pandemic might not behave as expected. Many people believe that infectious diseases like COVID-19 will wane as temperature rises since it first emerged in China in mid-December but pandemics often do not behave like this. Initial spread and outbreak suggest its likelihood to cold and dry conditions but pandemics don't act as seasonal outbreaks. A research paper entitled "High Temperature and High Humidity Reduce the Transmission of COVID-19" was published on March 9. In the paper, authors Jingyuan Wang, Kai Feng, Weifeng Lv of Beihang University and Ke Tang from Tsinghua University examined coronavirus (COVID-19) cases in 100 cities in China and their correlation to temperature and humidity. They concluded that "The arrival of summer and rainy season in the Northern Hemisphere can effectively reduce the transmission of COVID-19." Some other studies report that it's our immune system that is boosted up by Vitamin D more in summers than in winters that is suggesting the decrease in transmission of this condition. It is controversial as some studies report otherwise and argue that immune system is not only based upon vitamin D levels and no global studies supporting the decline in vitamin D levels in winters. Even if it has some seasonal variability then it is unlikely to just disappear in summers. Although studies are being done and data is being gathered, up till now, there is no solid proof that this virus will remain from December to April and will not affect in other months of year. So the need of hour is to take precautions on individual and government level to reduce the spread of this condition.

(The writer is PhD Microbiology and Molecular Genetics and Lab Incharge, Punjab AIDS Control Program)