With any vaccine still in early development, the best way to mitigate the pandemic is social distancing, he and other experts said. Because people may be passing the virus on to others even when they feel fine, asking only unwell people to stay home is unlikely to be enough. This is why many experts, going against recommendations by the CDC and the World Health Organization, are now urging everyone to wear masks — to prevent those who are unaware they have the virus from spreading it.