New Delhi: As the world battles the Covid-19 pandemic, there might be some hope with temperatures soaring. Reports suggest the new coronavirus may adhere to the distinct seasonality exhibited by its genetic cousins that have been around for many years.
The report published in Financial Times has some good news for the tropics as it suggests Covid-19 will find it harder to gain a foothold there than in the temperate regions of the planet.
Mohammad Sajadi, an associate professor at the University of Maryland’s Institute of Virology, said the virus will find it difficult to spread in warmer climates.
“Based on what we have documented so far, it appears the virus has a harder time spreading between people in warmer climates,” he said.
Scientists from Beihang and Tsinghua Universities in China examined coronavirus transmission in 100 cities across the country, concluding that “high temperature and high relative humidity significantly reduces the transmission of Covid-19”.
Sajadi observed that the virus can spread anywhere but the transmission is most effective between humans when humidity is low and the temperature is between 5 degrees Celsius and 11 degrees Celsius. As we see the virus spread, the most vulnerable regions lie between 30-50 degrees north of the equator like China and the US, and the southern portion of Europe.
The Maryland team predicted intensification in the temperate regions south of the equator during summer. There will be a drop in transmission with the arrival of summer as per researchers in China.
There was a note of caution from researchers at the University of Basel in Switzerland and the Karolinska Institute in Sweden conducting a larger study on the pandemic and studying seasonal patterns.
It was concluded that with the coming of spring and summer, there could be an impression that the virus has been successfully contained, “only for infections to increase again in the 2020-21 winter.”
With this there appears a similarity with the Spanish flu pandemic of 1918-19.
The theory that respiratory viruses behave seasonally is not well understood but one of the possible reasons is said to be that “although viruses multiply within people at the normal body temperature of about 37C, they survive and transmit better outside the human body at a much lower temperature and level of humidity,” said the report in FT.
Also in temperate regions people spend more time close together indoors.
Another scientific factor is that the human immune system is less effective in winter, partly because there is less sunshine to help in the production of vitamin D.
However, according to Marc Lipsitch, a Harvard University epidemiology professor there is an exaggeration of Covid-19’s likely seasonality.
He told FT, “We may expect modest declines in the contagiousness of [the virus] in warmer, wetter weather but it was not reasonable to expect these declines alone to slow transmission enough to make a big dent”.