Infectious Diseases

The authors propose that it is a scientific error to use lack of direct evidence of SARS-CoV-2 in some air samples to cast doubt on airborne transmission while overlooking the quality and strength of the overall evidence base.

There is consistent, strong evidence that SARS-CoV-2 spreads by airborne transmission.

Although other routes can contribute, the authors believe that the airborne route is likely to be dominant. The public health community should act accordingly and without further delay.

Summary:

If an infectious virus spreads predominantly through large respiratory droplets that fall quickly, the key control measures are reducing direct contact, cleaning surfaces, physical barriers, physical distancing, use of masks within droplet distance, respiratory hygiene, and wearing high-grade protection only for so-called aerosol-generating health-care procedures.

Such policies need not distinguish between indoors and outdoors, since a gravity-driven mechanism for transmission would be similar for both settings.

But if an infectious virus is mainly airborne, an individual could potentially be infected when they inhale aerosols produced when an infected person exhales, speaks, shouts, sings, sneezes, or coughs.

Reducing airborne transmission of virus requires measures to avoid inhalation of infectious aerosols, including ventilation, air filtration, reducing crowding and time spent indoors, use of masks whenever indoors, attention to mask quality and fit, and higher-grade protection for health-care staff and front-line workers.

Airborne transmission of respiratory viruses is difficult to demonstrate directly.

Mixed findings from studies that seek to detect viable pathogen in air are therefore insufficient grounds for concluding that a pathogen is not airborne if the totality of scientific evidence indicates otherwise. Decades of painstaking research, which did not include capturing live pathogens in the air, showed that diseases once considered to be spread by droplets are airborne.

Ten streams of evidence collectively support the hypothesis that SARS-CoV-2 is transmitted primarily by the airborne route.

The Centers for Disease Control and Prevention (CDC) warned in a document published Friday of "repeatedly documented" instances of coronavirus spreading through the air to people more than 6 feet away under certain conditions.

The new document explaining the latest understanding of how the virus spreads is part of a shifting emphasis towards airborne transmission of the virus.

"Transmission of SARS-CoV-2 from inhalation of virus in the air farther than six feet from an infectious source can occur," the new document says in large letters, while noting it is "less likely than at closer distances."

Some experts have been pushing the CDC for months to place a greater emphasis on airborne transmission and the need to improve ventilation, even with something as simple as opening the window in a room. Experts have also long said that outdoors is far safer than indoors.

The CDC acknowledged last year that the virus can spread through airborne transmission, but there has since been a growing emphasis on that method of transmission.

The agency emphasized that while it is updating its understanding of how the virus spreads, the same methods for keeping safe still apply. Wearing a mask, distancing from others, avoiding crowded indoor areas and allowing adequate ventilation are recommended.

read the story at https://thehill.com/policy/healthcare/552406-cdc-warns-virus-can-spread-more-than-six-feet-under-certain-conditions