A woman is tested for the coronavirus at a walk-up testing site Friday in Seattle. Testing availability and reliability continue to be problems in the U.S. fight against the virus.

Heather Brown, right, is tested for COVID-19 at a new walk-up testing site at Chief Sealth High School, Friday, Aug. 28, 2020, in Seattle. The coronavirus testing site is the fourth now opened by the city and is free. (AP Photo/Elaine Thompson)