The lack of universal recognition that COVID-19 is transmitted through airborne particles, along with unclear infection prevention recommendations, has led to a false sense of security that is putting the public at risk, especially in the midst of the reopening of workplaces, schools and universities, according to a research letter published today in Clinical infectious diseases.
Study authors Lidia Morawska, PhD, MSc, director of the International Laboratory for Air Quality and Health at the Collaborating Center of the World Health Organization (WHO) in Brisbane, Australia, and Donald Milton, MD, DrPH , MOH, from the University of Maryland at College Park, said they implore the medical community and policy makers to recognize that SARS-CoV-2 can spread through inhalation of microscopic respiratory droplets within 2 meters. (6.6 feet) or close to the infectious person.
A further 237 scientists around the world signed the research letter, which states that studies have shown “beyond a reasonable doubt” that the viruses released during normal breathing, talking and coughing are small enough to stay in air and pose a risk of infection to others nearby. For example, at typical indoor air speeds, a 5 micron (μm) (0.005 millimeter) particle can travel through a typical-sized room, settling from a height of 1.5 meters (3.3 feet) on the floor.
Lisa Brosseau, ScD, a nationally known expert in respiratory protection and infectious diseases and author of a comment on COVID-19 transmission published by CIDRAP, said the air route is traditionally defined as inhalation of respiratory pathogens only at a distance of the fountain. The study authors argue that there is a lot of evidence that infectious people also generate many small particles, which stay close to the source for long periods of time, said Brosseau, who calls this “aerosol transmission.”
Brosseau is a research consultant to the University of Minnesota Center for Infectious Disease Research and Policy, which publishes CIDRAP News.
Infectious virus in aerosols
The authors cited a study of video records of three people infected with COVID-19 in a poorly ventilated Chinese restaurant. The videos showed no direct or indirect contact between the three parties, leading investigators to conclude that the virus must have spread via the air route. And studies of other viruses such as respiratory syncytial virus (RSV) and Middle East respiratory syndrome (MERS) have shown that viruses can be exhaled and / or detected in the air from MERS isolation rooms.
“There are many reasons to expect that SARS-CoV-2 will behave similarly, and that transmission through airborne microdroplets is an important route,” they wrote. “Viral RNA associated with droplets less than 5 μm has been detected in the air, and the virus has been shown to survive equally well, if not better, in aerosols compared to droplets on a surface.”
While the current guidance of many international and national agencies recommends handwashing, physical distancing, and precautions against drops, most, including the WHO, do not recognize airborne transmission other than through generation procedures. of aerosols, such as intubations, performed in healthcare settings. The authors said they want the organization to redefine airborne transmission to include inhaling respiratory microscopic droplets near the infectious source.
CIDRAP Director Michael Osterholm, PhD, MPH agrees that the WHO must recognize that viruses like COVID-19 can spread via the air route. “The WHO has long had to face the blind spot it has had to accept the critical importance of airborne respiratory pathogen transmission such as influenza and SARS-CoV-2,” he said.
Brosseau agrees, saying the WHO does not want to recommend respirators for use in less developed countries. “I also think it is because his infection control advisers are uncompromising when it comes to thinking about inhaling aerosols near a source,” he said.
Hand washing, insufficient physical distance
The authors said that handwashing and physical distancing are appropriate, but not sufficient, to provide protection against respiratory droplets, particularly in poorly ventilated indoor environments, such as those that have been at the center of various “supersension” events. .
They recommend providing effective ventilation of indoor areas, including supplying clean outdoor air, minimizing recirculation, and supplementing with local exhaust gases, high-efficiency air filtration, and germ-killing ultraviolet lights, especially in public buildings, places work, schools, hospitals and nursing. houses. They also advise avoiding overcrowding, especially on public transportation and in buildings.
Noting that the guide does not cover the use of facial coatings in public, Brosseau said it is likely because “they will do very little to prevent the spread or stop inhalation of small particles.”
Recognizing that the evidence is incomplete for all modes of coronavirus spread, including microdrops, large droplets, and infected surfaces that are the basis of current guidance, the authors said the measures they propose offer more benefits than potential risks, even if they are only partially implemented.
Even low-cost measures like opening doors and windows can effectively increase air flow in many buildings, the authors said. The American Society of Heating, Ventilation, and Air Conditioning Engineers and the Federation of European Heating, Ventilation, and Air Conditioning Associations have already issued recommendations for mechanical systems.
“To control the pandemic, pending the availability of a vaccine, all routes of transmission must be discontinued,” the researchers wrote.
