Los Angeles residents are administered with a test for Covid-19 while in their vehicles inside the Crenshaw Christian Center in South Los Angeles Wednesday, March 25, 2020. | AP Photo All eyes on San Francisco Bay Area as nation's social distance bellwether

OAKLAND — The nation's grand social distancing experiment began 10 days ago in the San Francisco Bay Area, where health officials imposed the first shelter-in-place orders in a desperate bid to slow the spread of coronavirus.

California Gov. Gavin Newsom followed suit days later, touching off a cascade of states that imposed "stay at home" directives from New York to Louisiana.


The big question now: How will health experts know when Covid-19 infections are leveling off — and when will they feel confident enough to thaw restrictions? A lack of widespread testing and the novel biology of the virus pose challenges to deciphering the growth curve in the coming weeks.

The Bay Area will serve as a bellwether for when cities and states across the nation can emerge from hibernation — and the extent to which they can return to normal life. Besides being the tech capital of the world and home to cutting edge biomedical research, the region of 7 million people has everything from the cosmopolitan high-density city of San Francisco to expansive suburbs and rural enclaves, all in relative proximity.

But even in a region that prides itself on always being one step ahead, public health officials for now are still forced to rely on insufficient data, experience from other countries and anecdotes to determine if and when the contagion is flattening out.

Major health care organizations like Kaiser Permanente are relying in part on call center data to gauge how many people are reporting potential coronavirus symptoms. A geospatial analysis company is capturing smartphone data to detect whether people are reducing their movements. A reduction in Bay Area hospitalizations could show when the disease begins leveling off.

But none are fail-safe measures of the virus' containment.

“At this point, all one can do is to follow the case count,” said Jeffrey Martin, an epidemiologist at the University of California, San Francisco. “It’s actually an incredible situation in that the public is actually looking at the same thing the academics are looking at.”

The Bay Area has been on the forefront of identifying coronavirus outbreaks, with Silicon Valley’s Santa Clara County especially hard hit. As of Wednesday, the county of nearly 2 million people had confirmed 459 cases and 17 deaths — the most of any Bay Area county. Statewide, 2,535 Californians have tested positive for the virus and 53 people have died, according to Wednesday’s public health report, a delayed accounting of the actual number of cases.

Bay Area public health officials are frustrated they may not be able to test the volume of residents they need to accurately assess when the region has reached a peak and the number of cases starts to dwindle — the trend commonly referred to as “flattening the curve.”

With limited testing capacity, federal health officials are advising clinicians to use their judgment but test patients based on symptoms — fever, difficulty breathing, cough — as well as consider epidemiological factors such as how widespread community transmission is in the area.

If they can’t test widely, including those who lack symptoms, they say they simply can't have an accurate handle on how widespread the transmission is and how many people may be developing immunity from the virus. Early indications are that many people can have Covid-19 without symptoms.

How health officials interpret the data will impact all 40 million Californians. Newsom suggested this week that it will take 8 to 12 weeks to determine whether state measures have been effective. President Donald Trump said Tuesday that he hoped the nation could emerge from hibernation by Easter, which he described as "a beautiful time" to open up the economy.

“I wouldn’t be talking about relaxing this right now, but we need to be thinking about when we will know,” Martin said. “Whenever one lifts the foot off the breaks, there will be the possibility of a second round. Unless there’s a vaccine in place, there will be that possibility.”

Newsom feels confident California's efforts have already paid off. “We know it’s had an impact on bending the curve and buying us time,” the governor said Wednesday.

Kaiser Permanente, which covers 4.4 million members in Northern California and about 12.2 million systemwide, started conducting its own coronavirus tests last week, but has been hampered by a lack of testing swabs. Testing in the Southern California region is slated to start this week.

Kaiser, academic medical centers and hospitals are working with state public health officials to provide data on how many patients have been hospitalized and how many are on ventilators — another key data point in tracking.

In the meantime, Kaiser officials are monitoring calls about cold and cough symptoms to help determine the potential trajectory of the virus.

Typically, the call center receives about 4,000 calls a day as flu season picks up. On March 16, the day the six Bay Area counties announced the shelter-in-place order, Kaiser’s Northern California call center received 14,000 calls — an unprecedented number — about cold and cough symptoms. A week later, that number dropped to around 8,500 calls.

Stephen Parodi, an infectious disease specialist with The Permanente Medical Group in Northern California, said he hoped that number indicated that social distancing has started to work. The drop could also suggest more people are turning to home care to manage their illnesses; primary care visits have dropped by 60 percent as Kaiser patients have been urged to avoid doctor visits and seek care remotely via email, phone and telehealth.

“The ability to have a more defined approach to social distancing is going to be really important going forward,” said Parodi, the lead physician for Kaiser’s national coronavirus response. “If you can test large parts of the population, you can tell who is positive, who is negative, who needs to be socially distanced and who doesn't need to be socially distanced.”

Marin County Public Health Officer Matt Willis said testing bias is also a factor in trying to track the effectiveness of social distancing. Experts may not be able to distinguish whether trends are a function of additional tests or a change in the disease's spread.

“The number of cases reported in any one county or community is highly predicted by the number of tests being performed in that community. It makes it very difficult to understand the intrinsic scope of the epidemic,” Willis told POLITICO before he was diagnosed with the virus on Monday, becoming his county’s 39th Covid-19 case.

While many Bay Area residents appear to be complying with the order — streets are clear and commercial neighborhoods are near-ghost towns — some are not. Scores of residents flocked to regional parks and beaches over the weekend, prompting many to close and Newsom on Monday to order the closure of state-run parking lots at three dozen parks and beaches.

Confirmed coronavirus cases in California have been doubling every three to four days, California Health and Human Services Agency Secretary Mark Ghaly said Wednesday. But he noted testing is increasing, and credited staying at home and maintaining physical distance with helping to mitigate the expected rise in cases.

“We have early signs that some of these efforts are making a difference, and we believe that’s true in some pockets of the state,” Ghaly said.

Some early signals indicate that the Bay Area’s efforts may be starting to work.

UCSF epidemiologist George Rutherford said he’s seen significantly fewer Bay Area residents on the streets, indicating that most people are heeding the order and staying at home. He believes that estimates predicting up to 80 percent of Americans will get infected are too high.

In addition, he said he’s seen smaller increases in the number of cases in some counties than he saw earlier.

“What you’re really starting to see is the blunting of new cases,” Rutherford said. "The phenomenon is there. We're just not seeing the cases load.”