How Risky Is Aerosol Transmission of Covid-19?

The World Health Organization said on Thursday it doesn’t rule out the possibility of airborne transmission in crowded areas or indoor venues with poor ventilation, in an update of a scientific brief. However, the Geneva-based body said more research is needed, because in such cases, there may be alternative explanations as to how the people got sick, such as respiratory droplets that fell onto surfaces.

The WHO faces pressure from scientists led by Lidia Morawska, director of the International Laboratory for Air Quality and Health at Queensland University of Technology, who argue that hand-washing and physical distancing alone aren’t enough to stem infections.

“This problem is especially acute in indoor or enclosed environments, particularly those that are crowded and have inadequate ventilation,” Morawska and a colleague wrote in an open letter published this week and backed by 239 scientists. Officials must endorse other precautions such as increasing ventilation and avoiding recirculating potentially virus-laden air in buildings such as hospitals and schools, they said.

At stake isn’t what happens when an infected person coughs or sneezes globs of virus-laden liquid -- a long-established mode of infection -- but whether tiny particles known as micro-droplets and aerosols stay afloat long enough to be inhaled and cause infection deep in the lungs.

“Viruses can spread in this way and we need to be aware of that,” said Benjamin Cowling, head of epidemiology and biostatistics at the University of Hong Kong, who assisted China in the early study of transmission dynamics. “But that’s not to scare everybody.”

Morawska and others are calling on the WHO and similar bodies to recognize airborne transmission as a factor contributing to the spread of Covid-19, which has now sickened more than 11 million people.

Their push is gaining urgency as workplaces, schools, and colleges reopen. In the U.S., President Donald Trump rejected school-reopening guidelines that included increasing the circulation of outdoor air as too difficult.

“This is not rocket science,” Morawska said in an interview. “We know how to deal with ventilation.”

Some scientists point to the fact that the new pathogen hasn’t spread explosively across hospitals as evidence that it isn’t as contagious by air as flu or measles. The WHO says its existing recommendations, such as avoiding closed settings and ventilating indoor environments, do take into consideration the virus’s potential airborne nature. However, it stopped short of saying that such transmission is a proven threat in its scientific brief.

While the Morawska-led group recommended high-efficiency air filtration and germicidal ultraviolet lights be used, it also pointed to simpler protective measures, like supplying clean outdoor air and avoiding overcrowding on public transport.

“Ventilation can be particularly important,” said the University of Hong Kong’s Cowling, who reviewed the letter. “Spending time outdoors can be a really good thing to do to avoid the risk of transmission of Covid-19.”

The WHO needs to concede that the new coronavirus can spread via the airborne route, according to Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

“We are long overdue for the WHO to confront the blind spot it has had for accepting the critical importance of airborne transmission of respiratory pathogens,” he said Monday in his center’s daily news bulletin.

Morawska, 67, started looking at airborne transmission of infectious disease after the SARS epidemic. During the outbreak, she was asked by the WHO to join a team of aerosol scientists to investigate contagion at Hong Kong’s Amoy Gardens housing estate, where a virus-laden plume emanating from a patient with diarrhea was implicated in hundreds of cases.

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[Machster]

This is why you need to be wearing a real respirator when entering a public building. You can buy a half mask respirator with P100 filter (HEPA) cartridges online. About $30 to $50 bucks. North and 3M are both well known brands but there are others. If fitted properly and there is no beard growth, and a good face seal, they can provide 100% filtration of virus particles. The next best is a N95 or P95. They provide up to 95% filtration down to 0.3 microns (individual virus particles 0.15 microns are rare, they are usually stuck to other particles or water so they are larger). If you have questions check out the NIOSH website. They approve respirators for OSHA (the agency that protects workers who work in hazardous jobs such as asbestos). Make sure the respirator you wear is NIOSH approved. They have a posted a useful table of international testing on various brands of N95s. Face coverings won't protect you because they do not filter the air you breathe.

[nuraful]

wtf is this music? we are not talking some happy things..