SACRAMENTO — Gov. Gavin Newsom warned Monday that the rate of transmission of the coronavirus is creeping back up in the most populous regions of the state, putting at risk the decline in new cases that California has seen in recent weeks.
The effective reproduction number — which represents the average number of people to whom each infected person spreads the coronavirus — is near or above 1 in the Bay Area and Southern California, Newsom said, meaning the number of new cases could soon begin rising again there.
“While it’s true we have seen a threefold decrease in the total number of cases since our peak in July, we are seeing early signs that those decreases are beginning to slow down,” Newsom said during a news conference. “They’re beginning to plateau as it relates to total number of new cases.”
Most of California is still slowly emerging from a second shutdown over the summer, as Newsom ordered bars, indoor dining, gyms, houses of worship, hair salons and many other newly reopened businesses closed again following a post-Memorial Day surge in coronavirus cases.
By July, the average number of daily new infections reached more than 10,000. That has dropped to 3,367 over the past week, Newsom said Monday, with fewer than 3% of tests statewide coming back positive.
But under a new tiered reopening plan unveiled last month by Newsom, counties with low rates of the virus that have begun to allow those sectors to operate again could be forced to shutter them for a third time if their transmission totals take a turn for the worse.
In the broader Bay Area — San Francisco, Alameda, Marin, Contra Costa, Solano, Sonoma, Napa, San Mateo, Santa Clara and Santa Cruz counties — the effective reproduction number has increased to 0.95, from less than 0.9 a month ago.
In the lower part of Southern California — encompassing Imperial, Orange, Riverside, San Bernardino and San Diego counties — the number is 0.97, and it has reached 1.02 for the upper region of Southern California: Kern, Los Angeles, San Luis Obispo, Santa Barbara and Ventura counties.
A reproduction rate of 1 means every person will infect one other, and a disease outbreak will neither grow nor decline. To slow down spread, the rate needs to stay below 1.
State health officials have raised concerns that an uptick in coronavirus cases tied to Labor Day celebrations could lead to an 89% increase in hospitalizations over the next month.
“This is again what science had predicted if we go back to our original form,” Newsom said. “If we’re not cautious, if we’re not vigilant, if we’re not wearing our masks, if we’re not practicing social distancing, physical distancing and hand washing and hygiene, these numbers can start to tip back up.”