Fear of the spreading coronavirus is causing a global run on sales of face masks despite medical experts’ advice that most people who aren’t sick don’t need to wear them. In South Korea this week, hundreds lined up to buy masks from pharmacies and discount stores. Shortages started cropping up in Asia soon after the outbreak became a crisis in China. Now many places have sold out of masks, while others are limiting sales per customer. Amazon is policing its site, trying to make sure sellers don’t gouge panicked buyers. Still, the U.S. Centers for Disease Control says only people who are sick or have symptoms like fever and shortness of breath should wear masks. Others should wash their hands, disinfect commonly used surfaces and avoid touching their face.