The US CDC updated guidance on its website to say coronavirus can commonly spread "through respiratory droplets or small particles, such as those in aerosols," which are produced even when a person breathes. "Airborne viruses, including COVID-19, are among the most contagious and easily spread," the site now says. Previously, the CDC page said that Covid-19 was thought to spread mainly between people in close contact -- about 6 feet -- and "through respiratory droplets produced when an infected person coughs, sneezes or talks."