At this point, the research supports the value of wearing a face mask plus taking other precautions like eye protection, physical distancing, and hand hygiene. Masks alone are not enough.
Meta-analysis Study published in The Lancet June 27 2020
What they did: The research team examined virus transmission among people on six continents. Here's a quote from the article:
We did a systematic review of 172 observational studies in health-care and non-health-care settings across 16 countries and six continents; 44 comparative studies were included in a meta-analysis, including 25 697 patients with COVID-19, SARS, or MERS.Conclusions so far:
The risk for infection is highly dependent on distance to the individual infected and the type of face mask and eye protection worn. From a policy and public health perspective, current policies of at least 1 m physical distancing seem to be strongly associated with a large protective effect, and distances of 2 m could be more effective. These data could also facilitate harmonisation of the definition of exposed (eg, within 2 m), which has implications for contact tracing.
Eye protection might also add substantial protection. For the general public, evidence shows that physical distancing of more than 1 m is highly effective and that face masks are associated with protection, even in non-health-care settings, with either disposable surgical masks or reusable 12–16-layer cotton ones, although much of this evidence was on mask use within households and among contacts of cases. Eye protection is typically underconsidered and can be effective in community settings. However, no intervention, even when properly used, was associated with complete protection from infection. Other basic measures (eg, hand hygiene) are still needed in addition to physical distancing and use of face masks and eye protection.Transmission during speech
An experimental study in the New England Journal of Medicine (May 2020) tested the transmission of oral droplets during speech. The louder the speech, the more droplets. Masking reduced considerably reduced the droplets as can be seen in the video.
Transmission and Face Masks
A study in Nature Medicine from April 2020.
"We identified seasonal human coronaviruses, influenza viruses and rhinoviruses in exhaled breath and coughs of children and adults with acute respiratory illness. Surgical face masks significantly reduced detection of influenza virus RNA in respiratory droplets and coronavirus RNA in aerosols, with a trend toward reduced detection of coronavirus RNA in respiratory droplets. Our results indicate that surgical face masks could prevent transmission of human coronaviruses and influenza viruses from symptomatic individuals."
Questions and answers from scientists at Stanford University
Rather than repeat this lengthy advice, I will just offer the link for those who want more details on wearing masks. https://med.stanford.edu/news/all-news/2020/06/stanford-scientists-contribute-to-who-mask-guidelines.html
Note
Everything in this post is subject to change. That is the way of science. New studies may suggest a better practice or reveal what is not working. I realize it can be confusing to those who want absolute knowledge about what to do. Perhaps it helps to remember that so many advances in medical and psychological science have helped people live longer and enjoy better quality of life for decades.
Staying healthy when people transmit viruses:
Use the three Ws = Wearing masks, Washing hands, Watching distance
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