Effects of temperature variation and humidity on Covid-19

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By Dr.Abdul Razak Shaikh

A team of researchers unveiled the results of a new study that looked at how temperature and humidity may affect the transmission of COVID-19, the illness caused by the new coronavirus.

According to researchers findings high temperature and high relative humidity significantly reduce the transmission of COVID-19. An increase of just one degree Celsius and 1% relative humidity increase substantially lower the virus’s transmission, according to the data analyzed by the researchers.

The study is the latest in a limited but growing body of research, not all of which has been peer-reviewed, that examines the effect of weather on the spread of the SARS-Cov-2 virus, which causes the COVID-19 illness.

Like some other respiratory viruses such as the flu is there a chance that the new Coronavirus will spread less as temperatures increase?

A new study has found that the new coronavirus, named SARS-CoV-2, didn’t spread as efficiently in warmer and more humid regions of the world as it did in colder areas. Though the early analysis, published in the journal Social Sciences Research Network, is still under review, it provides a glimpse into what we might expect in the warmer months to come.

Qasim Bukhari and Yusuf Jameel, both from Massachusetts a state of the northeastern US, Institute of Technology, analyzed global cases of the disease caused by the virus, COVID-19, and found that 90% of the infections occurred in areas that are between 37.4 and 62.6 degrees Fahrenheit (3 to 17 degrees Celsius) and with an absolute humidity of 4 to 9 grams per cubic meter (g/m3). (Absolute humidity is defined by how much moisture is in the air, regardless of temperature.)

In countries with an average temperature greater than 64.4 F (18 C) and an absolute humidity greater than 9 g/m3, the number of COVID-19 cases is less than 6% of the global cases.

This suggests that the transmission of the 2019-nCoV virus might have been less efficient in a warm humid climate so far.

Humidity especially might play a role, given that most of the transmission of COVID-19 has happened in relatively less humid areas.

But that doesn’t mean that when summer rolls around, social distancing will be obsolete and people will once again pack into bars and concerts like sardines.

For most of North America and Europe, the effect of humidity on the spread of the coronavirus would be negligible until June when levels start to increase beyond 9 g/m3, the authors wrote. The role of warmer temperatures in slowing the spread might be observed only at much higher temperatures.

Therefore its implication will be limited at least for northern European countries and the northern U.S., which do not experience such warm temperatures until July, and that too for a very short time window. So the chances of reducing the spread of COVID-19 due to these environmental factors would be limited across these areas.

It’s unreasonable, I think, at this point to expect that the virus will quote-on-quote disappear during our summer months, said Dr. William Schaffner, an infectious disease specialist at Vanderbilt University in Tennessee, who was not part of the study. Still, I think it might give us a little bit of hope, Schaffner said.

The spread of some respiratory viruses, such as the flu viruses diminishes in high humidity and high temperatures. It’s not exactly clear why temperature and humidity affect the flu virus or other seasonal viruses, but it’s in part because when you exhale, some virus at the back of your throat gets pushed out into the air, Schaffner told Live Science. If we were to get a microscope and look at that virus, we would discover that it’s surrounded by a microscopic sphere of moisture called a droplet.

When you have low humidity in the wintertime, that sphere of moisture tends to evaporate, which means that the virus can hover in the air for a longer period of time because gravity won’t pull it to the ground, Schaffner said. But in the summer, when you exhale a viral particle, the surrounding droplet doesn’t evaporate, which means it will be heavier and gravity will pull it out of the air much more readily. In other words, it doesn’t hover as long as it does in the winter, making it less likely to infect the person close by.

Transmission of the flu goes down to very low levels during the summer, so we don’t typically have to worry about it very much in warmer months. But other viruses, such as the Corona Virus Strains that cause the common cold, have a seasonal distribution that is not as dramatic as influenza.

Still, we can’t count on the warmer and humid months to slow the spread of the virus, Schaffner said. We have to beware of wanting to walk only on the sunny side of the street, there’s another side that’s shadier.

The scientists’ findings align with what some experts have suspected about weather’s impact, including Hong Kong University pathology professor John Nicholls, who told AccuWeather that research on a lab-grown copy of SARS-CoV-2, in cold environments there is longer virus survival than the warm ones.

Other infectious disease experts have voiced skepticism that warmer weather will help curb the spread of COVID-19.

The transmission of viruses can be affected by a number of factors, including climate conditions (such as temperature and humidity), population density and medical care quality. Therefore, understanding the relationship between weather and the transmission of COVID-19 is key to forecast the intensity and end time of this epidemic.