• To contract COVID-19, you have to be exposed to a sufficient amount of the virus. Research suggests that it takes at least 1 million copies of the virus to cause infection.
  • Transmission of the virus via face-to-face contact with an infected person is far more likely than catching it from touching a contaminated surface.
  • Prolonged exposure is defined as 15 minutes or more of unprotected contact with someone less than 6 feet away.
  • The longer you are exposed to a person, the more of their virus-infected respiratory droplets you are exposed to.  A person wearing a mask will expose others to fewer respiratory droplets than one without a mask.
  • Fresh air can dilute the concentration of the respiratory droplets, which lowers the likelihood of transmission. Interacting with people outdoors is safer than indoors.


Six months into the coronavirus crisis, there’s a growing consensus about a central question: How do people become infected?

It’s not common to contract Covid-19 from a contaminated surface, scientists say. And fleeting encounters with people outdoors are unlikely to spread the coronavirus.

Instead, the major culprit is close-up, person-to-person interactions for extended periods. Crowded events, poorly ventilated areas and places where people are talking loudly—or singing, in one famous case—maximize the risk.

These emerging findings are helping businesses and governments devise reopening strategies to protect public health while getting economies going again. That includes tactics like installing plexiglass barriers, requiring people to wear masks in stores and other venues, using good ventilation systems and keeping windows open when possible.


Read the full article by Daniela Hernandez, Sarah Toy and Betsy McKay at WSJ.com