What we’ve learned: COVID-19 tests, contagion, immunity

A man is tested for coronavirus disease (COVID-19) at a Los Angeles fire department testing station for the homeless on Skid Row, in Los Angeles, California, U.S., April 21, 2020. Credit: REUTERS/Lucy Nicholson.

The U.S. now has about a million confirmed coronavirus cases. Epidemiologist Janet Hamilton says many different tests have been manufactured, and their accuracies vary. She also explains the different (and sometimes intermittent) symptoms, the role of air quality and temperature in the virus’ survival, and whether you’re immune to another infection if you’ve recovered from COVID-19.