Vox: The World Health Organization (WHO) on Friday announced changes to its guidelines on who should wear a mask during the Covid-19 pandemic and where they should wear it. The new guidance recommends that the general public wear cloth masks made from at least three layers of fabric “on public transport, in shops, or in other confined or crowded environments.” It also says people over 60 or with preexisting conditions should wear medical masks in areas where there’s community transmission of the coronavirus and physical distancing is impossible, and that all workers in clinical settings should wear medical masks in areas with widespread transmission. It’s a major update to the agency’s April 6 recommendations, which said members of the general public “only need to wear a mask if you are taking care of a person with Covid-19” or “if you are coughing or sneezing.” And it’s important advice for countries around the world battling the virus, especially those in South America, the Middle East, and Africa, where the rate of Covid-19 transmission appears to be accelerating. [h/t Pete Weiss]