Health officials announced another case of the new coronavirus in Silicon Valley, adding to the more than 30 who've had the virus in California. Residents in Northern California are at the epicenter of what officials are calling a turning point in the spread of the highly contagious coronavirus in the U.S.

Investigators are rushing to retrace the steps of a patient they believe to be the first known person in the U.S. to be infected without traveling internationally or being in close contact with anyone who had it. The woman first went to the hospital in Vacaville, between San Francisco and Sacramento.