In a new advisory, the government has warned that the SARS-CoV-2 virus can be transported through air as well in the form of aerosols, and infect people up to 10 metres away. The warning, included in an updated general advisory on Covid-19 issued by the office of the Principal Scientific Advisor, is in line with the latest evidence that suggests that airborne transmission of the virus, especially in enclosed spaces, cannot be ruled out.
Newsletter | Click to get the day’s best explainers in your inbox
Droplet vs aerosol
The different modes of transmission of the virus has been the subject of intense discussion since the start of the pandemic. It was initially suggested that the virus spreads predominantly through large droplets that come out when a person is talking, sneezing or coughing. These droplets, because of their large size, were supposed to travel only short distances before falling on the ground. A person 6 feet (2 metres) away was considered safe from infection.
Over the months, however, scientists have been finding increasing evidence of the virus travelling through aerosols as well. Aerosols are small solid particles suspended in the air. Relatively light, aerosols can carry the virus to much larger distances. Also, they can remain suspended in the air for several minutes, or even hours, thereby greatly increasing the chance of the infecting a nearby person.
In an updated note on Covid-19 transmission, the US Centers for Disease Control and Prevention has said though the chances of an infection gets reduced significantly at distances greater than six feet, such incidences had been “repeatedly documented under certain preventable circumstances”.
The new advisory
The Indian advisory has adopted a cautious approach, and warned that transmission through aerosols could happen even at a distance of 10 metres. Droplets coming out from an infected person fall within a two-metre distance, while aerosols can be carried be carried in air up to ten metres, it has said.
It has said that droplets and aerosol remain the main modes of transmission of the disease, although it has also warned of the possibility “surface transmission” — droplets falling on different surfaces, and getting picked up by people who touch these surfaces. The risk from surface transmission, considered very high in the initial months of the pandemic, is now believed to be greatly reduced. The CDC has said current evidence “strongly” suggested transmission from contaminated surfaces “does not contribute substantially to new infections”.
What you should do
The advisory asks people to keep their indoor spaces well-ventilated, by keeping doors and windows open, and using exhaust systems. “In closed, unventilated indoor spaces, droplets and aerosols become quickly concentrated and greatly increase the risk of transmission to the people in the area,” it says.
It stresses that the infection transmission risk was much lower in outdoor areas since the virus particles get easily dispersed.
It advises introducing outdoor air in offices, homes and larger public spaces, and measures to improve ventilation in these spaces in urban and rural areas alike. “Simple strategic placement of fans, open windows and doors, even slightly open windows can introduce outdoor air and improve the air quality inside. Introduction of cross ventilation and exhaust fans will be beneficial in curtailing the spread of the disease,” it says.