Turns out most COVID-19 infections are spread by people who show no symptoms at all—another reason why it's good to wear masks and take other simple precautions, according to the US Centers for Disease Control and Prevention. "CDC and others estimate that more than 50% of all infections are transmitted from people who are not exhibiting symptoms," the agency says... "This means at least half of new infections come from people likely unaware they are infectious to others." The CDC explains that 24% of coronavirus transmitters are asymptomatic, 35% presymptomatic, and 41% were experiencing symptoms. That means 59% were transmitted by people without symptoms.

The CDC attributes the finding to two studies, one of which was published in July by the Proceedings of the National Academy of Sciences. Led by experts in the US and Canada, it was based on "recent individual-level data" showing that "the majority of incidences may be attributable to silent transmission." It added that "consequently, even if all symptomatic cases are isolated, a vast outbreak may nonetheless unfold," and "over one-third of silent infections must be isolated to suppress a future outbreak below 1% of the population." The CDC concludes that people can help curb the virus by wearing masks, washing their hands, cleaning and disinfecting surfaces, using ventilation, and avoiding crowded indoor spaces.