Transmission

Aboard the Diamond Princess, a Case Study in Aerosol Transmission

“We’re getting surprises all the way along,” Dr. Conly said. “This paper I find interesting, but it has a long way to go to be able to get into a line of credibility, in my mind.”

Dr. George Rutherford, a professor of epidemiology at the University of California, San Francisco, was equally skeptical. He said that, outside of hospital settings, “large droplets in my mind account for the vast majority of cases. Aerosols transmission — if you really run with that, it creates lots of dissonance. Are there situations where it could occur? Yeah maybe, but it’s a tiny amount.”

Dr. Tang and other scientists strongly disagree. “If I’m talking to an infectious person for 15 or 20 minutes and inhaling some of their air,” Dr. Tang said, “isn’t that a much simpler way to explain transmission than touching an infected surface and touching your eyes? When you’re talking about

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W.H.O. to Review Evidence of Airborne Transmission of Coronavirus

After hundreds of experts urged the World Health Organization to review mounting scientific research, the agency acknowledged on Tuesday that airborne transmission of the coronavirus may be a threat in indoor spaces.

W.H.O. expert committees are going over evidence on transmission of the virus and plan to release updated recommendations in a few days, agency scientists said in a news briefing.

The possibility of airborne transmission, especially in “crowded, closed, poorly ventilated settings, cannot be ruled out,” said Dr. Benedetta Allegranzi, who leads the W.H.O.’s committee on infection prevention and control.

She said the agency recommends “appropriate and optimal ventilation” of indoor environments, as well as physical distancing.

Agency staff fielded several questions from reporters about transmission of the virus by air, prompted by an open letter from 239 experts calling on the agency to review its guidance. Many of the letter’s signatories have collaborated with the W.H.O. and served

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W.H.O. Finally Endorses Masks to Prevent Coronavirus Transmission

Long after most nations urged their citizens to wear masks, and after months of hand-wringing about the quality of the evidence available, the World Health Organization on Friday endorsed the use of face masks by the public to reduce transmission of the coronavirus.

Since the beginning of the pandemic, surprisingly, the W.H.O. had refused to endorse masks. The announcement was long overdue, critics said, as masks are an easy and inexpensive preventive measure.

Even in its latest guidance, the W.H.O. made its reluctance abundantly clear, saying the usefulness of face masks is “not yet supported by high quality or direct scientific evidence,” but that governments should encourage mask wearing because of “a growing compendium of observational evidence.”

The W.H.O. also provided an exhaustive list of the potential disadvantages of wearing a mask, including “difficulty with communicating clearly” and “potential discomfort.”

A study funded by the W.H.O. concluded this week that

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