Why Researchers Hope to Test High-Risk Groups in California

In his 20 years in and out of homelessness, Ollie Harris, 69, has seen a lot of things. But what happened on a recent Friday was new.

Sitting outside his tent on a patch of ground he and his wife staked out near Lake Merritt, he watched a white van pull up and two women step out wearing surgical masks and latex gloves.

“Would you like to be tested today?” one of them asked. “I might as well,” Mr. Harris replied. A nurse quickly swabbed Mr. Harris’s nostrils and throat and then jotted down his information.

Mr. Harris was one of the first people tested under a new type of collaboration that has emerged as a distinctive feature in California’s fight against Covid-19.