Harvard scientists: California needs to double testing to contain coronavirus surge – San Francisco Chronicle

California must increase its current daily testing more than twofold to control the worsening spread of coronavirus, according to new estimates released this week by the Harvard Global Institute.

The adjusted goals come as cases have been swelling across the country, and some states have seen positive cases vastly outpace their ability to test.

California has been keeping up with the spike in new cases by performing an average of 215 tests per 100,000 people per day, or about 85,000 tests per day..

But the recent rise in cases means that California will have to do far more testing to manage and reduce the spread of the virus.

California now needs to do 564 tests per 100,000 people per day, or about 223,000 tests per day, to mitigate the reach of the virus in the state. To actually suppress coronavirus, the state should be doing multiple times that: 2,088 tests per 100,000 people per day, or about 825,000 tests per day. The estimates were produced by the Harvard Global Institute, a research group focused on public policy, and a collaboration of scientists and public health experts around the country.

“We still have to do more tests,” Gov. Gavin Newsom said Wednesday, noting the state is meeting its stated goal of conducting 60,000 to 80,000 tests a day.

A spokeswoman for the California Department of Public said the state’s testing capacity will continue increasing but did not specifically address the Harvard figures.

Dr. Thomas Tsai, a surgeon and health policy expert at the Harvard T.H. Chan School of Public, cautioned that the new goals are more like goal posts that can shift as case rates change. If measures like wearing masks and social distancing are able to bring case rates down, for instance, less testing will be needed.

But for now, he said, the state needs to “keep moving the testing needle up” to understand the true spread of the coronavirus and reduce it.

“California is a good cautionary tale,” said Tsai, noting that the state led the country in aggressive shelter-in-place orders that stemmed infections and only began reopening after case rates had dropped.

“It shows you that even in a state that has done well, how important it is to stay vigilant, because the pot is always on the verge of boiling over,” he said. “If you are only keeping up with the bare minimum of testing all you are doing is barely keeping the lid on the pot.”

Like other states in the country, coronavirus cases in California have been accelerating in recent weeks as the economy has reopened. Prison and nursing home outbreaks have been behind some of the surge, but so too have increased social gatherings. On Tuesday, the state recorded 7,820 new cases — its second-highest tally in a 24-hour period. On Wednesday there were 5,898. Hospitalizations and admissions to intensive care units have also been spiking.

As of Sunday, California, along with 12 other states, was classified as “orange” on the risk scale developed by Harvard and the collaboration of scientists. Orange indicates escalating community spread. Stay-at-home orders may be necessary, unless it’s possible to increase testing and tracing. Three states, Arizona, Florida and Mississippi, were classified as “red,” meaning that community spread is unchecked and stay-at-home orders are necessary.

Cynthia Dizikes and Catherine Ho are San Francisco Chronicle staff writers. Email:,, Twitter: @Cat_Ho, @CDizikes

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