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What Is Contact Tracing and Why Is It Crucial to Reopening California?

Contact tracers are key to controlling the spread of an infectious disease, public health experts say

Thousands of public employees and volunteers are training to become contact tracers for the state of California, beginning a crucial step in the statewide fight to stop the spread of coronavirus and reopen businesses for cash-strapped citizens. But what exactly is contact tracing and why is it critical to easing the state out of current restrictions?

Contact tracers must identify individuals who test positive for COVID-19 and help them self-isolate to prevent further spread. They then gather a list of all of the people who came into close contact with the infected individual, communicate with that list of contacts to warn them they were potentially exposed and provide self-isolation information or testing services. They must also monitor the symptoms of each person in that list of contacts until their test results are returned or they pass the 14-day incubation period.

Traditional contact tracing is a laborious but crucial method to help manage the spread of a viral epidemic as the nation awaits a successful vaccine or prophylactic treatment. According to a white paper from the Johns Hopkins Center for Health Security, an infected individual is estimated to infect an average of two to three other people. “This means that if 1 person spreads the virus to 3 others, that first positive case can turn into more than 59,000 cases in 10 rounds of infections,” the paper said.

As the state begins to slowly reopen and people begin to relax on following physical distancing guidelines, a newly infected individual’s contacts will grow — and make contact tracing even more difficult. And until there are more (and better) COVID-19 tests available in the supply chain, there is the risk that asymptomatic individuals can slip through the cracks of traditional contact tracing and trigger more chains of infection, Robert Siegel, a Stanford microbiology and immunology professor, told TheWrap.

Thus, contact tracing and testing are just “a piece of the puzzle” in managing the pandemic, Siegel said. “Testing and contact tracing does not take the place, for instance, of making sure you avoid infection and washing your hands and wearing a mask,” he said.

The first goal, Siegel said, is to decrease the probability of transmission down to less than one person per case. “Once that happens, then the number of cases begins to fall. And what you want to do is … bring that number of cases down to zero,” he said. “Once that happens, it’s still critically important to have in place excellent contact tracing because, just like in China, there’s always the possibility that someone from the outside can reintroduce the virus.”

The contact tracers need to work quickly — a task that could be difficult if new infections continue to climb. California reported 1,759 new confirmed cases on Tuesday alone. 

“On average, people become symptomatic in about five to six days after exposure and we can find the virus, on average, two days before they become symptomatic. So you might have three days, on average, to get them,” John Swartzberg, an infectious diseases and vaccinology specialist at the UC Berkeley-UCSF Joint Medical Program, told TheWrap. “The longer it’s going to take me to identify these people and to get them in quarantine, the greater the chance these people are going to have to spread the disease.”

Contact tracers and state agencies must also determine if an infected individual has a safe place to self-isolate and the resources to sustain themselves and, if not, connect them with public services to help. Also, some individuals can’t be contacted through the phone or email, meaning that contact tracers may have to go and knock on doors or engage in other methods.

The process also has privacy implications, especially when technology like cellphone apps are used to facilitate the process. The state of Washington is requiring all restaurants that resume dine-in service to keep a log of all patrons — with names, phone numbers and emails — for at least 30 days to aid tracers seeking potential contacts for any newly infected people.

Some companies, like Apple and Google, are developing apps that take advantage of smartphone Bluetooth technology to help determine whether a user has been in close contact with someone who has tested positive for COVID-19. Many of these apps have precautionary measures in place to protect people’s identities, but there still remains concern that apps — some of which use smartphones’ GPS data — could be used to track citizens’ movements or otherwise allow the government to collect sensitive data on users. And that is a catch-22 when it comes to public health. “The more anonymity you preserve, the less public health can use that data to control the pandemic,” Swartzberg said.

In the meantime, a statewide program led by the University of California, San Francisco, is training 10,000 civil servants to be contact tracers and relies on “low level” technology like phone calls, texts, emails and management software to help the contact tracers stay organized, George Rutherford, the head of UCSF’s Division of Infectious Disease and Global Epidemiology, said. “This is really shoe-leather stuff. You’ve got to interview people, you’ve got to be able to talk to them and you’ve got to be able to convince them that they should, that they need to participate,” he said.

But given the sheer number of new infections in the state, a more efficient and longer-term system will necessitate some combination of these detective-like contact tracers and smartphone apps, health experts told TheWrap. Once a sustainable system is worked out, health experts also emphasized the need to maintain contact tracing resources beyond this pandemic.

“We’re sort of reinventing what we should have been doing all along,” Swartzberg said. “It would have been really nice if we started this [pandemic already] with a robust contact tracing program for other communicable diseases and then just ramped that up.”

As with any early-stage program, there are bound to be bumps along the way as California attempts to expand its contact tracing capabilities. But through those bumps, the state hopes to emerge with a stronger public health system than before.

“Ultimately, it will work. Ultimately, we’ll figure out all these things and it will work,” Swartzberg said. “But it’s going to be a slog.”

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