New Delhi: The United States Centers for Disease Control and Prevention (CDC) has updated its public guidelines on the transmission of SARS-CoV-2, the virus which causes coronavirus (COVID-19).
As of May 7, 2021, there were three majors updates by CDC that said the transmission of SARS-CoV-2 can occur from inhalation of virus in the air farther than six feet from an infectious source, SARS-CoV-2 is transmitted by exposure to infectious respiratory fluids and that the risk of SARS-CoV-2 infection varies according to the amount of virus to which a person is exposed.
Transmission of COVID-19 from inhalation of virus in air:
According to CDC, with increasing distance from the infectious source, the role of inhalation likewise increases. "Although infections through inhalation at distances greater than six feet from an infectious source are less likely than at closer distances, the phenomenon has been repeatedly documented under certain preventable circumstances," the Scientific Brief read.
It stated that these transmission events have involved the presence of an infectious person exhaling virus indoors for an extended time (more than 15 minutes and in some cases hours) leading to virus concentrations in the air space sufficient to transmit infections to people more than 6 feet away. Whereas, in some cases, it can transmit infections to people who have passed through that space soon after the infectious person left.
As per CDC, the factors that increase the risk of SARS-CoV-2 infection under these circumstances include:
1. Enclosed spaces with inadequate ventilation or air handling within which the concentration of exhaled respiratory fluids, especially very fine droplets and aerosol particles, can build up in the air space.
2. Increased exhalation of respiratory fluids if the infectious person is engaged in physical exertion or raises their voice (eg, exercising, shouting, singing).
3. Prolonged exposure to these conditions, typically more than 15 minutes.
Transmission of COVID-19 by exposure to infectious respiratory fluids
The CDC said that the principal mode by which people are infected with COVID-19 is through exposure to respiratory fluids carrying the infectious virus.
They stated that exposure occurs in three principal ways:
1. Inhalation of very fine respiratory droplets and aerosol particles.
2. Deposition of respiratory droplets and particles on exposed mucous membranes in the mouth, nose, or eye by direct splashes and sprays.
3. Touching mucous membranes with hands that have been soiled either directly by virus-containing respiratory fluids or indirectly by touching surfaces with the virus on them.
Earlier on April 16, The Lancet journal has said that there is strong evidence to fore that the SARS-CoV-2 virus is predominantly transmitted through the air. The report stated that public health measures that fail to treat the virus as predominantly airborne leave people unprotected and allow the virus to spread.
