The US Centers for Disease Control and Prevention (CDC), a national public health institute, asserted that the COVID-19 can spread through microscopic respiratory particles known as an aerosol that can move in the air for minutes or even hours before being inhaled.
This type of transmission has infected even those who maintained social distancing while CDC warned that the chances of getting infected are high in crowded, poorly ventilated indoor spaces.
Independent experts have been researching for months and trying to grab CDC’s attention on the super spreading events like the choir practice in the US state that infected dozens of people and the role of aerosols in it.
Some researchers even stated that the CDC hasn’t made enough in-depth studies, as the agency maintains that it is still “more likely” for the virus to spread by floating through larger respiratory droplets that quickly fall on people in the neighborhood.
Mr Donald K. Milton, a University of Maryland environmental health professor and expert on aerosols, stated that CDC is slowly moving in the right direction “but is not where I would quite like to see it.”
Professor Milton added that research shows that aerosols containing the virus particles are more likely to spread the disease compared to the larger droplets spewed like gunshots, even if the infected person is less than six feet away.
“At close range, you’re still going to see aerosol transmission dominant most of the time. Spitballs are much less frequent.”
Professor Milton further said that the masks, which the agency has always stressed to be worn when near others, can be used both indoors and outdoors to curb the spread of the virus.
Outdoor dining has a higher risk of spreading the infection as large number of people are sitting at one place for a long time without masks. It is better to keep moving while outdoors as it could lower the risk of aerosol inhaling, he said.
When the pandemic outbreak began in the United States, CDC asked people to maintain social distancing and to wash their hands in case they happened to touch a contaminated surface. But later, the agency itself said that the infected surfaces have a small role in spreading the virus.
With the increase in super-spreading incidents, researchers claimed that aerosols appeared to be the main reason and they requested CDC and WHO to accept the occurrence of airborne transmission, but the authorities remained skeptical. Super spread refers to the situation when a very few number of infected people spread the disease to a large group at a progressive rate.
WHO’s revision
In July, after about 239 researchers from 32 countries signed an open letter urging the WHO to acknowledge the possibilities of aerosol’s role in spreading the virus, the international agency revisedits guidelines to recommend that people avoid poorly ventilated, crowded spaces. But WHO continued to claim that the aerosol transmission has not been clearly proved.
A letter written by Milton and five other researchers and published by Science magazine cited “overwhelming evidence” that inhalation was “a major transmission route” for the coronavirus and cited an urgent need to define terms consistently across scientific fields.
The letter stated that the aerosols that are said to be particles smaller than 100 microns, “can remain suspended in the air for many seconds to hours, like smoke.”
Professor Milton said that smoking is a perfect example to say how tiny respiratory particles are floating through the air. “If somebody goes out for a smoke and they come in and you smell it on their breath, you’re inhaling their exhaled breath.”
