The United States Centers for Disease Control and Prevention on Friday said that the primary reason through which many are getting infected with the SARS-CoV-2 virus was very fine aerosolised particles transmitted during respiration. It added that the “risk of transmission is greatest within three to six feet of an infectious source”, where the most concentration of the very fine particles occurs.
“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, and (3) touching mucous membranes with hands that have been soiled either directly by virus-containing respiratory fluids or indirectly by touching surfaces with virus on them,” the statement read.
The American medical agency said that people release respiratory fluids during various activities, including exhalation through quiet breathing, speaking, exercise, singing, coughing and sneezing. It is these droplets that carry and transmit the virus.
“The largest droplets settle out of the air rapidly, within seconds to minutes,” the statement said. “The smallest very fine droplets, and aerosol particles formed when these fine droplets rapidly dry, are small enough that they can remain suspended in the air for minutes to hours.”
The transmission occurs through three principal ways, the American medical body said. First, through inhalation of the air carrying very small fine droplets and aerosols that contain the virus. Second, deposition of the virus carried in droplets and particles onto exposed mucous membranes, through “splashes and sprays”.
“With increasing distance from the source, the role of inhalation likewise increases,” the body said. “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.”
These transmissions, the agency said, have involved the presence of those infected exhaling indoors for more than 15 minutes to an hour. The American agency said this has led to “virus concentrations in the air space sufficient to transmit infections to people more than 6 feet away, and in some cases to people who have passed through that space soon after the infectious person left”.
The agency reiterated that factors that increase the risk of a Covid-19 infection were “enclosed spaces with inadequate ventilation or air handling”, “increased exhalation” and “prolonged exposure”, which means for more than 15 minutes.
Among effect prevention measures of a Covid-19 infection were current recommendations like physical distancing, well-fitting masks, good ventilation and avoiding crowded indoor spaces, the medical body said.
Globally, the coronavirus has infected 15.72 crore people and killed over 32.78 lakh since the pandemic broke out in December 2019, according to Johns Hopkins University. Over 9.33 crore people have recovered from the infection.
India, which has been tackling the second wave of the pandemic, has been struggling to keep up with the rising demands of medical equipment, oxygen and drugs amid an acute shortage.
On Saturday, World Health Organisation Chief Scientist Soumya Swaminathan said the coronavirus variant spreading in India was more contagious and might be evading the protection offered by vaccines. In an interview, the scientist said that these factor were contributing to the massive outbreak of the infection in the second wave.
The B.1.617 variant of the Covid-19, known more commonly as the double mutant strain, was first detected in India in October last year. As the name suggests, the strain involves two variants of the virus. The E484Q mutation has characteristics of a previously detected variant – the E484K – which was seen in the fast-spreading Brazilian and South African variants, making it highly transmissible. The L452R mutation, on the other hand, helps the virus evade the body’s immune response. The double mutation strain was subsequently named B.1.617.
India on Sunday registered 4,03,738 new coronavirus cases in the last 24 hours, taking the tally of infections in the country to 2,22,96,414 since the pandemic broke out last year. The country’s toll climbed by 4,092 deaths to 2,42,362. India now has over 37 lakh active cases and 1,83,17,404 recoveries.