Researchers reviewed studies on indoor relative humidity and the spread of coronavirus and concluded that low humidity promotes infection.
There is increasing evidence of airborne transmission of the new coronavirus. The World Health Organization (WHO) already recognizes that Sars-CoV-2 spreads through this route and new research corroborates this.
One of them was recently published in the journal Aerosol and Air Quality Research, conducted by scientists from the Leibniz Institute for Tropospheric Research (TROPOS), in Germany, and the CSIR National Physical Laboratory, in India.
The researchers noted that the transmission of the new coronavirus through aerosol particles occurs mainly in indoor environments with low humidity.
To conduct the investigation, the team reviewed the 10 most relevant international studies published between 2007 and 2020 analyzing the influence of humidity on the survival, spread and infectious capacity of pathogens that cause influenza and the coronaviruses Sars-CoV-1 (Sars), Mers -CoV (Mers) and Sars-CoV-2 (Covid-19).
The results indicate that humidity influences the spread of coronavirus in three different ways: 1) the way microorganisms behave in the contaminated droplets; 2) the survival or inactivation of viruses on surfaces; 3) the influence of airborne dissemination in low humidity environments.
Although low humidity makes infected droplets dry faster, the virus’s survival rate remains high.
“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,” said Dr. Ajit Ahlawat, of TROPOS.
This is of particular concern during the winter, when the air tends to be drier. When the air humidity is high, the droplets grow quickly, fall to the ground, and are less likely to be inhaled.
“A humidity level of at least 40 percent in public buildings and local transport would therefore not only reduce the effects of COVID-19, but also of other viral diseases such as seasonal flu,” said Dr. Sumit Kumar Mishra, of CSIR.
Scientists advise that in countries with low temperatures, high humidity must be ensured indoors. In hot, tropical locations, people should not use too much air conditioning – which also dries out the air.
The ideal is to keep the room ventilated with fresh air, and of course: maintain social distancing, avoid crowds, and use an effective face mask whenever possible.