How temperature enhances the spread, kills coronavirus at home and offices-Experts
London, August 21, 2020 (AltAfrica)-The airborne transmission of the coronavirus SARS-CoV-2 via aerosol particles in indoor environment seems to be strongly influenced by relative humidity
This is the conclusion drawn by researchers from the Leibniz Institute for Tropospheric Research (TROPOS) in Leipzig and the CSIR National Physical Laboratory in New Delhi from the analysis of 10 most relevant international studies on the subject.
The evaluation covered studies between 2007 and 2020 by other researchers who investigated the influence of humidity on survival, spread and infection with the pathogens of influenza and the corona viruses SARS-CoV-1, MERS and SARS-CoV-2.
Result shows that air humidity influences the spread of coronavirus indoors in three different ways: (a) the behavior of microorganisms within the virus droplets, (b) the survival or inactivation of the virus on the surfaces, and (c) the role of dry indoor air in the airborne transmission of viruses
Although low humidity causes the droplets containing viruses to dry out more quickly, the survivability of the viruses still seems to remain high.
Therefore, the team concludes that other processes are more important for infection: “If the relative humidity of indoor air is below 40 percent, the particles emitted by infected people absorb less water, remain lighter, fly further through the room and are more likely to be inhaled by healthy people. In addition, dry air also makes the mucous membranes in our noses dry and more permeable to viruses,” summarizes Dr. Ajit Ahlawat
The new findings are particularly important for the upcoming winter season in the northern hemisphere, when millions of people will be staying in heated rooms. “Heating the fresh air also ensures that it dries.
In cold and temperate climate zones, therefore, the indoor climate is usually very dry during the heating season. This could encourage the spread of corona viruses,” warns Prof. Alfred Wiedensohler of TROPOS. The air humidity determines how much water a particle can bind
At higher air humidity, the surface of the particles changes considerably: a kind of water bubble forms—a miniature ecosystem with chemical reactions. The liquid water content of aerosols plays an important role in many processes in the atmosphere, as it influences the optical properties, leading for example to haze or altered effects of aerosols on the climate.
At a higher humidity, the droplets grow faster, fall to the ground earlier and can be inhaled less by healthy people. “A humidity level of at least 40 percent in public buildings and local transport would therefore not only reduce the effects of coronavirus, but also of other viral diseases such as seasonal flu.
Authorities should include the humidity factor in future indoor guidelines,” demands Dr. Sumit Kumar Mishra of CSIR—National Physical Laboratory in New Delhi.
For countries in cool climates, the researchers recommend a minimum indoor humidity. Countries in tropical and hot climates, on the other hand, should take care that indoor rooms are not extremely undercooled by air conditioning systems. When air is extremely cooled, it dries out the air and the particles in it, making people inside the room feel comfortable. But the dry particles will remain in the air for longer duration.
From a researchers’ point of view, more attention should be paid to indoor air to prevent future outbreaks of viral disease. The moisture content of indoor air is an important aspect but not the only one.
Fresh air from outside can also reduce the risk of transmission. And of course, the measures already known and practiced: Keep social distancing, having as few people per room volume as possible, and wearing masks. The lowest risk of infection still where there are no viruses in the air. Tilo Arnhold
Therefore, they recommend controlling the indoor air in addition to the usual measures such as social distancing and masks.
A relative humidity of 40 to 60 percent could reduce the spread of the viruses and their absorption through the nasal mucous membrane.
To contain the COVID-19 pandemic, it is therefore extremely important to implement standards for indoor air humidity in rooms with many people, such as hospitals, open-plan offices or public transport, writes the research team in the scientific journal Aerosol and Air Quality Research.
According to the WHO, the coronavirus SARS-CoV-2 has led to at least 21 million infected persons and over 750,000 deaths worldwide in over half a year.
The health and economic effects of the pandemic pose major social challenges for practically all countries. Worldwide, therefore, ways are being sought to stem the spread of the virus in order to avoid drastic measures such as lockdowns and contact restrictions
For a long time, the main transmission route of viral droplets was considered to be direct human-to-human contact, because of infected people sneezing or coughing and secreting the virus.
Because these drops are relatively large and heavy, they fall very quickly to the ground and can only cover very short distances in the air. The recommendation to keep a minimum distance of 1.5m to 2m (social distancing) is based on this assumption.