https://www.mercurynews.com/2020/02/26/coronavirus-heres-what-the-latest-science-tells-us/

A Solano County resident appears to be the nation’s first case of coronavirus infection from an unknown source, fueling concern that the virus could spread undetected in the general population.

Unlike other cases, the person did not recently return from a foreign country and is not known to have had contact with a person who was sick or infected, according to the U.S. Centers for Disease Control.