A second person in Northern California has been infected with the coronavirus without having any known risk factors, such as travel to China or exposure to somebody known to be infected.

The findings hints that the coronavirus may already circulating locally in California, passing from person to person.

Earlier this week, a person who had no known risk factors tested positive for the virus in Solano County, between San Francisco and Sacramento. The new infection is in Santa Clara County, south of San Francisco, which includes the city of San Jose; it was confirmed by Dr. Sara Cody, the county’s public health director.

Hundreds of Americans who were potentially exposed to the virus in Asia have been quarantined at military bases in California, including Travis Air Force Base in Solano County.

A whistle-blower complaint made public on Thursday alleged that federal health officials were sent into quarantine areas at the bases without proper training or protective gear, and then were allowed to roam around, on and off the bases.