According to a recent study, “Humidity is a key factor in the spread of Covid-19”. The study has been published in the journal Transboundary and Emerging Diseases. The study focussed on the Greater Sydney area during the early epidemic stage of Covid-19. It observed the association between humidity and community transmission.
The study found that for every 10 per cent decrease in relative humidity, Covid-19 cases increased by an estimated 2-fold in the area where the study took place.
According to the researchers, the dry air is possibly responsible for the increase in the spread of Covid-19. This could mean that climate has a role to play in Covid-19 spread which raises serious concerns on the prospect of seasonal outbreaks of the infection. However, no association between rainfall, temperature or wind and COVID-19 has been found yet.
This is how COVID-19 spread increases in lower air humidity: When the humidity in the air is low, the air becomes drier and dry air makes the aerosols (which are smaller in size than droplets) smaller. And when an infected person sneezes and coughs in air, then the virus transmitted to aerosols can linger in the air for longer. Because of which risk of virus spread to other people increases.
But if the air is humid, aerosols will be present in larger and heavier form due to which they fall and hit surfaces quicker, reducing the exposure of virus present in the air to other people.
The study authors commented, “The need (is) for people to wear a mask, both to prevent infectious aerosols escaping into the air in the case of an infectious individual and exposure to infectious aerosols in the case of an uninfected individual”.
An earlier study published in the Canadian Medical Association Journal has claimed to found no association between temperature, latitude and the spread of the Covid-19 infection.