evidence: For months, the Centers for Disease Control and Prevention maintained that the only people who needed to wear face masks were people who were ill or those who were treating them. That notion stemmed from the idea that basic medical masks do little to protect wearers, and instead primarily prevent sick people from spewing infectious droplets from their noses and mouths. Plus, limited supplies needed to be prioritized for frontline health workers. The World Health Organization agreed. [...] At the same time, other scientists point to lab studies that indicate a broader adoption of masks, even of less effective do-it-yourself models, could still be helpful. And it’s possible widespread mask use could keep people from touching their faces and help convey the severity of the pandemic. [...] Other scientists, however, disagree, and say that while masks won’t be fully effective, they are likely to be better than nothing.