In January and most of February, there were few or no community tests in California.
The CDC has only provided test materials to certain health services, with restrictions that limited testing and therefore follow-up of the new coronavirus to those who were sick or exposed to someone already known to have COVID-19 . The federal agency has focused on cruise ships, with Princess Cruises’ Diamond Princess carrying the largest known group of COVID-19 cases outside of China. The first passenger tested positive for COVID-19 five days after leaving Japan on January 20. In the end, 712 passengers and crew members tested positive, and nine of them died.
COVID-19 did not reappear in the Bay Area until February 27, when doctors finally decided to test a hospitalized woman who had been sick for weeks. It has become the first case of coronavirus widespread in the region.
But from there, almost all of the positive tests indicated local spread. “When public health [officials] tried to trace the onset of the disease … we were unable to find a specific contact, “Smith told county supervisors. This means that the virus is already in the community – not, as the CDC suspected, as only in China and spread through contact with China. ”
Researchers still don’t know how long the virus has been hiding in blood banks and other stores now to see if persistent antibodies can show them what’s been left behind. A study funded by the National Institutes of Health looks for viral antibodies in samples from blood banks in Los Angeles, San Francisco and four other cities across the country.