Controlled Clinical Trial of Mask Use in Households to Prevent Respiratory Virus Transmission

Background: Observational epidemiologic data suggest that transmission of viral respiratory infection was significantly reduced during the SARS epidemic with the use of face mask as well as other infection control measures. However, there are no prospective randomised control trials on face masks in prevention of viral respiratory infections Aims: To determine the efficacy of surgical masks and P2 masks in households on the interruption of transmission of respiratory viruses.

Methods: Prospective cluster randomized trial comparing surgical masks, non-fit-tested P2 (respirator) masks with no masks in interruption of viral transmission between household members. Families of children presenting to emergency department with influenza like illness (ILI) were randomised to one of the three groups and followed up for development of respiratory illness in other family members. Nasopharyngeal swabs of index patients and contacts that developed ILI were tested with a multiplex respiratory viral PCR for influenza A and B, parainfluenza, RSV, picornavirus, enterovirus, rhinovirus, adenovirus, coronaviruses human metapneumovirus.

Face mask rules for Bay Area: When do I have to wear one?

Several counties and cities across the Bay Area now require residents to wear face coverings in some public settings, following health orders intended to curb the spread of the coronavirus. Here’s a look at what you need to know about how face masks or coverings slow the spread of the coronavirus: Q: Why do I need to wear a mask? A: The virus that causes COVID-19 is most commonly transmitted through respiratory droplets when an infected person sneezes or coughs. These droplets can remain suspended in the air for up to three hours and be transmitted at least 13 feet by aerosols that are emitted by breathing or speaking, based on reports by the CDC.

Masks are effective in blocking, or at least limiting, your exposure to these contagious viral droplets and aerosol particles. Because we do not always know who is infected (many coronavirus cases are asymptomatic), you should also wear a mask to protect others. Officials in San Francisco, Alameda, Contra Costa, Marin, San Mateo and Sonoma counties in addition to the cities of Berkeley, Pleasant Hill and Fremont have mandated that people use basic nonmedical, cloth masks, including scarves and bandannas, to cover their noses and mouths when they leave home to go to the doctor, grocery store or other essential places.


Health officials in Santa Clara and Napa counties said that they are strongly urging all individuals to wear face coverings when out of their homes to perform essential activities but stopped short of compelling people to wear masks. While the best way to prevent transmission of the virus is to stay home, if necessary, to go out for an essential errand, health officials require people to wear face coverings to slow the spread of the virus.

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