US CDC updates Covid-19 guidelines to include aerosol transmission

WASHINGTON: The US Center for Disease Control on Friday updated its guidance to confirm that the coronavirus also spreads through so-called "aerosol transmission." This effectively means the pathogen transmits and proliferates through not just close contact but also by inhalation of very fine particle mist exhaled by an infected person which can remain suspended in the air.
Although such transmission has long been factored in by many researchers and public health officials, the updated guideline now stressing that inhalation is one of the main ways the virus is spread is a change from the agency’s previous position that most infections were through close contact and surface transmission.
"Modes of SARS-CoV-2 transmission are now categorized as inhalation of virus, deposition of virus on exposed mucous membranes, and touching mucous membranes with soiled hands contaminated with virus," the updated guidance reads. Although the guidance maintains that "the principal mode by which people are infected is through exposure to respiratory fluids carrying infectious virus," it says the virus can also be transmitted in poorly ventilated and/or crowded indoor settings, because “aerosols remain suspended in the air or travel farther than 1 meter.”
Some experts and public health officials had worried that the CDC had underplayed such airborne aerosol transmission, which would make not just social distancing but even personal distancing imperative, even in a family where one person bears the risk of exposure. The guidance implicitly endorses the advice that masking AND distancing, not to speak of ventilation, is important even in closed family situations.
Although the fine differentiation between aerosol/fine mist and droplets might seem like pettifogging to some, experts said it could have and still lead to important public health and behavioral guidelines. For instance, it may be better to be outdoors, with social distancing, than be cooped up indoors with other people -- even family members who are exposed to risk -- in closed, poorly-ventilated spaces.
"If the importance of aerosol transmission had been accepted early, we would have been told from the beginning that it was much safer outdoors, where these small particles disperse more easily, as long as you avoid close, prolonged contact with others. We would have tried to make sure indoor spaces were well ventilated, with air filtered as necessary. Instead of blanket rules on gatherings, we would have targeted conditions that can produce superspreading events: people in poorly ventilated indoor spaces, especially if engaged over time in activities that increase aerosol production, like shouting and singing. We would have started using masks more quickly, and we would have paid more attention to their fit, too. And we would have been less obsessed with cleaning surfaces," one expert wrote on an NYT OpEd.
The updated guidelines puts a question mark on the three-feet distancing in classrooms that schools in US have used to reopen, suggesting it may need to be revised, although the country has ramped up vaccination to such a degree that it is set to begin delivering them to adolescents next week. The number of people who have received at least one shot in the US ticked over 150 million on Friday, about 46 per cent of the population.
Separately, the CDC also began reviewing estimates of Covid-19 deaths in US and across the world amid commentary and criticism that it is being vastly underestimated. An analysis by the Institute for Health Metrics and Evaluation (IHME) in Washington pegs the global death toll from the pandemic at nearly 6.9 million and the US count at more than 900,000, far more than the current official figure of 3.25 million and 580000 respectively.