Coronavirus: Here’s how it spread in Santa Clara County

With a diverse and well-traveled populace, Santa Clara County is especially vulnerable to contagion.   Yet the arrival of a new virus went completely undetected, giving it time to widely seed our region before we even knew it was here.

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With a diverse and well-traveled population, Santa Clara County is especially vulnerable to contagion.

Yet the arrival of a new virus early this year went completely undetected, giving it time to widely seed our region before we even knew it was here, the county’s top public health official says. By early March, that virus, called COVID-19, was so widespread that three TSA agents at San Jose International Airport contracted it not from each other but from entirely separate sources.

In an exclusive interview, county health officer Dr. Sara Cody revealed the depth of the containment challenge facing the county, Northern California’s hardest-hit location — and why infections exploded so quickly, demanding an aggressive “shelter-in-place” order.

“The vast majority of cases are randomly scattered” in Santa Clara County, not clustered in the small and easily identifiable groups seen in some other locations, she said in a Friday interview, one of the few she has given since the crisis began.

Ideally, officials would deploy disease detectives to each of the 302 patients in the county, asking questions that could help disrupt the social network of coronavirus: Did they play bridge last week? Did they join a book club? Which aisles did they shop at Home Depot, Walgreens and Safeway? Who are their friends and family? And who are their friends and family?

“We don’t have a workforce to do that,” said Cody. “And that’s a real problem. Because we need to be able to interrupt every chain of transmission that we possibly can.”

The very nature of Santa Clara County puts it at risk, she said.  We’re diverse, with residents from all over the globe. And we’re travelers, with easy access to three international airports.

Other Bay Area counties share those same characteristics, helping to explain why our region’s total case count soared to 694 on Sunday. While the number of cases in adjoining counties fall short of Santa Clara County’s total of 302, they are still high, with 117 in San Mateo, 108 in San Francisco, 106 in Alameda and 61 in Contra Costa County.

If this illness was a wildfire, there would be no single giant inferno. Instead, it’s many far-flung hotspots.

Most cases are mild and don’t require hospitalization. Given the shortage of available tests, they may not even be detected. Yet people with minor illness can unwittingly transmit the virus to others, with catastrophic consequences for an estimated five percent of those affected.

As early as January, local physicians called the county Department of Health to report illnesses that didn’t meet the formal U.S. Centers for Disease Control definition for coronavirus symptoms — but were suspect.

“We were not able to test them. There just wasn’t the capacity to do that,” because the patients weren’t eligible under the CDC’s strict testing criteria, Cody said.

“We absolutely missed people. No question,” she said. “All the people that were ‘return travelers’ with very mild symptoms — we weren’t testing them,” she said. We couldn’t test their friends or family members, either, she added.

“It was like looking through a slit lamp,” she said, referring to a narrowly-focused microscope commonly used in eye exams. “You just can’t see as broadly as you need to.”

It wasn’t until late February that the county finally got federal approval to start running tests in its own laboratory.

Immediately, she sensed that the problem might be far larger than imagined.

The very first test conducted by the county came back positive — and the patient, a woman in her 60s, had no history of international travel or contact with a traveler or infected person. How and where was she exposed? No one knew. That told Cody that the virus was lurking in the general population.

“It was a real signal, a game changer,” said Cody. “That indicated that somehow she was exposed to the virus somewhere in our county, although we didn’t know where. … That was our first signal that we had transmission in our community.”

Cody was further alarmed when three Transportation Security Officers at Mineta San Jose International Airport also tested positive.

These workers had no links to each other — showing that they didn’t catch the illness from each other but from independent exposure in a community where the virus was already running rampant.

“TSA workers work in a place where they’re in contact with incredible numbers of the traveling public. … I can’t think of another type of worker who is exposed to so many people in a day,” she said. “So they’re sentinels.”

“What that cluster represented,” she recalled, “was: ‘Wow, we have a significant amount of community transmission.’ ”

Confronted with early outbreaks like this, countries such as Singapore and Taiwan launched aggressive “contact tracing” programs that discover the details of where patients live, play and work. Close contacts of patients are quarantined to limit viral spread.

The Chinese city of Wuhan, the epicenter of the outbreak, brought in 1,500 epidemiologists to conduct “contact tracing,” assigning five experts to every single case, according to Dr. Michele Barry, Senior Associate Dean for Global Health at Stanford University’s School of Medicine.

“We can’t use that same strategy” due to short staffing, said Cody. “Trying to map and figure out where are some hotspots for transmission — we really don’t have the data to enable us to do that. That’s still a pretty fuzzy part of the picture.”

Instead, the country is focusing its efforts on detecting outbreaks when they occur in easily recognized groups — particularly among people who are at high risk, such as residents of long-term care facilities, she said.

“We want to know as fast as we can and both remove them from the group and test them to prevent a chain of transmission in a highly vulnerable group,” she said.

That’s also why the county deployed an early “shelter-in-place” order. Because experts can’t detect and encircle each and every case, the general community needs to protect itself through distancing, she said.

Early on, we were “well behind where we needed to be to understand the magnitude of transmission that was occurring in the community — undetected and unbeknownst to us,” she said. “But we are where we are.”

“What can we do now?” she asked. “That’s the focus.”