Test delays, rising cases taking toll on tracing
Counties missing goals for logging virus spread
Contact tracing — finding and notifying everyone who has had close contact with a person infected with the coronavirus — is key to stemming the pandemic. Once people learn they’ve spent time near someone who had the virus, they can get tested themselves and quarantine so they don’t infect others.
Bay Area county health departments ramped up in April and May to handle the laborious process, most of it armchair detective work by phone and email, not the hightech surveillance some in Silicon Valley originally envisioned. But the recent surge in cases has made the task much harder, because there are more people to contact and because it takes longer to be tested and then get the results.
Alameda, Contra Costa, Marin, San Francisco, San Mateo and Santa Clara counties all fall short of their goal of doing case investigations for 90% of the people who test positive, and then reaching out to 90% of the folks
those people had close contact with while they were infectious.
Napa, Sonoma and Solano counties did not respond to requests for information.
When it comes to reaching contacts of the people who tested positive, the counties range from 70% to 80%, except for Contra Costa, which reaches only 26% of those who had contact with infected people, and Marin, which reached only 46% (its numbers are older). Still, those numbers are far better than those in New York and some other states.
“Obviously we want as many as possible because that’s where you get the most bang for your buck,” said Dr. George Rutherford, an infectious diseases expert at UCSF who spearheaded San Francisco’s contacttracing program. But modeling shows that even reaching 43% of infected people’s contacts provides some disease suppression. “I think the spread would be worse without” contact tracing, even though it hasn’t reached its potential, he said.
Contra Costa County could not say why it is so far below the Bay Area norm, especially since it is closer than Alameda and San Mateo counties to meeting its contact tracing staff goal.
“We’ve been grappling with it,” said Erika Jenssen, deputy director of Contra Costa Health Services. “To do effective contact tracing, we need timely lab results for tests, adequate staffing and to partner with the community.”
She pointed to delayed test results as a major obstacle. While the median turnaround time in the county is four days, many results come in as late as 10 days after testing — by which time a person may not longer be infectious.
And it’s not just results that take a while: In parts of the Bay Area, some people must wait a week or more for a testing slot to open up.
The case investigations — interviews with newly diagnosed people — shed light on how the virus has spread since shelterinplace orders were eased.
“We are seeing more people who were at some kind of gathering; that’s a common source of exposure,” Jenssen said. Contra Costa County investigators found that 18% of those who tested positive had attended large gatherings in the previous 15 days, while 17% had been to inperson workplaces. About 20% had visited restaurants, supermarkets and other stores.
Even counties that have maintained fairly high contact tracing numbers say they struggle with the surge.
“We want to be able to have a sustained conversation with all of the contacts, but when the numbers spike up, it diminishes our ability to do that,” said Kimi Watkins
Tartt, director of the Alameda County Public Health Department. “The conversations are little more clipped.”
Since cases in the county have more than doubled to about 150 to 200 a day, up from 60 to 80 in early June, the interaction often just covers the basics, she said: You’ve been in contact with someone who tested positive, please contact your provider, here’s how to quarantine.
Followup calls to see whether contacts have tested positive or developed symptoms have also had to go by the wayside for now.
Rutherford said contact tracers can prioritize people whose test results show they had high viral loads and thus were more infectious, as well as those who were working in communal settings. If test results are delayed, he said, “you just move on. There’s a short shelf life for contact tracing.”
Counties said most infected people average only about three to five close contacts, although that number has ticked up recently as shutdown orders eased. Sometimes people testing positive have already alerted those contacts, though a phone call from a tracer may still be useful in explaining the importance of quarantining.
All the counties offer support, including housing and food deliveries, to people who test positive and those identified as their contacts, to help them quarantine or isolate themselves. Most said that many people took advantage of food deliveries, but only a handful, including unhoused people and those in very crowded living situations, chose to move into the hotel rooms rented for the purpose. For instance in Santa Clara County, only 2.5% of cases and their contacts requested housing.
With 900 contact tracers — a combination of reassigned county workers, community volunteers and state workers — Santa Clara County has the region’s largest tracing workforce.
“We’ve been able to keep up with the surge,” said Dr. Sarah Rudman, assistant public health officer in Santa Clara County. “Even on days when we had on the order of 250 new cases, we have had the staffing to call them and the contacts they generated.”
Still, the team is speaking to only threequarters of cases and then reaching 70% of those cases’ contacts.
Gonzalo Riccombeni, a communicable disease investigator with Santa Clara County, explained the case investigation process.
First, the investigator verifies full name and date of birth. They explain they’re calling because the person has tested positive for the coronavirus. They ask if the person has any symptoms, is able to isolate themselves, and if they need any resources, such as a hotel room or food deliveries. They ask who the person spent time with two days before symptoms or 14 days before testing positive, and get those people’s phone numbers. They offer to answer any questions.
“The biggest challenge is getting people to answer their phones,” he said.
“We’ve been super fortunate in San Francisco to develop a pretty welloiled machine around our contact tracing efforts,” said Dr. Darpun Sachdev, who leads case investigation and contact tracing at the San Francisco Department of Public Health. The rapid increase in cases means sometimes “we may not be able to reach people for whom we get delayed test results,” she said. The team focuses on people who were tested within the past seven days.
“It would be ideal if the (testing) turnaround were faster,” she said.
All the counties emphasize
“It would be ideal if the (testing) turnaround were faster.” Dr. Darpun Sachdev, San Francisco Department of Public Health
some basic points. All contact tracing information is confidential. They never ask about Social Security numbers, financial information or immigration status. They strive to be culturally competent, including having multilingual staffs with additional interpreters available by phone.
Alameda County has only about a third of its goal of 300 contact tracers. It is working to partner with local health clinics to boost its contact tracing staff with people who are already working in the community and expects to have its full complement by late September or early October.
Most people are receptive to the calls, which often show up on caller ID as “CA. COVID Team.”
“It’s a smaller percentage who are suspicious and resistant,” said Tuere Anderson, clinical director for the Alameda County Health Care Services Agency’s Center for Health Schools and Communities. “We have a great team to build rapport very quickly and overcome that hump to get them to trust us with some information and give us their time to hear what we have to share.”
In Marin, where the outbreak at San Quentin State Prison has caused numbers to spike, officials say contact tracing is not effective, especially given testing lags.
The county is no longer “expecting this sort of almost clinical model, where you’re testing individuals and expecting that single test results lead to contact investigations, and then trying to isolate that individual in a hotel and offer them food assistance and income support,” said Dr. Matt Willis. “All those things are critical, but when you’re getting 50 to 60 new cases a day, that strategy just isn’t feasible.”
Other public health experts also emphasize that contract tracing is far from a panacea.
“We can’t contact trace our way out of this surging epidemic; it’s moving too quickly,” said George Lemp, an infectious disease epidemiologist and former director of the HIV/AIDS Research Program at the University of California Office of the President. “Contact tracing will only be partially helpful. It was meant for slowermoving outbreaks and investigations of clusters from specific sources and events.”