Governor Gavin Newsom told Californians they should only leave their homes when necessary during the pandemic.
He earlier estimated more than half of the 40 million people in his state would contract Covid-19 in just the next two months.
The virus has claimed 205 lives in the US and infected more than 14,000.
Globally nearly 250,000 patients have tested positive for the respiratory illness and more than 10,000 have died.
