April 29, 2020

States across the country are laying the groundwork to launch massive contact tracing efforts to identify people who may have contracted the new coronavirus. Some public health experts say the efforts are crucial to relaxing social distancing measures intended to curb America's Covid-19 epidemic. But how does it work?

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States prepare to ramp up contact tracing efforts

Public health officials say widespread testing for the new coronavirus and contact tracing for those who test positive are crucial to safely reopening nonessential businesses and easing social distancing measures intended to slow the virus' spread.

Now, as many states are eager to ease loosen those restrictions—and, in some cases, already are—some are working to implement contact tracing efforts. For instance, an NPR survey of 41 states and the District of Columbia found respondents reported a total of about 7,324 contact tracers and plan to increase that number to more than 35,500. In addition, about half of the states surveyed said they are considering using smartphone data or online apps to assist with contact tracing.

CDC Director Robert Redfield said the agency has deployed 500 staff to assist with contact tracing, and the agency plans to provide $45 million to support another 650 contact tracing positions.

Researchers estimate the United States will need between 100,000 and 300,000 contact tracers to adequately track the new coronavirus' potential spread and identify Americans who might have been exposed to the virus. However, NPR's survey indicates that only one state, North Dakota, currently has enough workers per capita to perform adequate contact tracing, and only Michigan, Nebraska, and Washington, D.C., have plans  in place to reach the needed amount of workers.

According to the survey, the average rate of contact tracers among the states was 12 per 100,000 people, which is a third of what experts project states will need to combat the country's coronavirus epidemic—and some states indicated they didn't have a plan to hire more contact tracers, NPR's "Shots" reports.

Former CDC Director Tom Frieden, said, "There are some states that are really thinking about this and scaling it up," and "there are others that are just beginning to think about it."

How does contact tracing work?

For contact tracing to work, a team of public health workers must quickly follow up with people newly diagnosed with the novel coronavirus to identify any individuals who may have come in contact with the patient while they were infectious.

According to "Shots," the goal is to have people who were exposed to the virus to isolate themselves, in hopes of preventing the virus from spreading any further. Contact tracing also can help public health officials identify outbreaks and their causes early, the Milwaukee Journal Sentinel reports.

Because people infected with the new coronavirus sometimes show mild or no symptoms of Covid-19, the disease caused by the virus, containing the virus is particularly difficult, according to Joel Hersh, former director of the bureau of epidemiology at the Pennsylvania Department of Health. That makes contact tracing especially necessary to curbing the new coronavirus' spread.

So what would contact tracing for the new coronavirus look like?

1. Identifying the index case

First, contact tracers would have to identify and contact the "index case," or a person who was recently diagnosed with Covid-19, within 24 hours of the diagnosis. Due to the nature of Covid-19, the best way to identify the index case is through testing for the new coronavirus, according to Bruce Lee, a professor of health policy and management at the City University of New York.

Then, contact tracers would have to determine how long the index case was infectious by figuring out how much time passed since the index case was initially infected with the virus. To do so, public health workers have to calculate the virus' incubation period, which can be between two and 14 days for the new coronavirus. From there, workers determine the length of time a patient was infectious by summing the number of days the patient was asymptomatic but likely infected and the number of days they patient showed symptoms of infection.

2. Identify, reach out, and isolate contacts

Next, contact tracers interview the index case about their whereabouts during their infectious period to find out how many people the index case had "effective" contact with during that time. Lee explained that effective contact includes only the types of contact through which the pathogen possibly could be transmitted. For the new coronavirus, effective contact can include physical contact like a hug or handshake, as well as standing within six feet of an infected person for 15 minutes or more, ABC News reports.  

During this stage, the individual must try to recall the names of those with whom they may have had effective contact. Contact tracers then work to locate those contacts, inform them that they were exposed to the new coronavirus, and recommend they self-isolate for 14 days to prevent them from exposing others.

If the contacts self-isolate, "[t]he viruses then have nowhere to go," said John Swartzberg, a clinical professor emeritus in the infectious diseases and vaccinology division at the University of California Berkeley School of Public Health.

3. Contact follow-up

The final step is for contact tracers to maintain a connection with people who may have been exposed to the virus. Tracers follow up with the contacts to see if they are developing symptoms of Covid-19, and instruct them to contact a physician as needed.

If a contact ends up testing positive for the new coronavirus and reveals that they have made their own effective contacts, tracers begin the process all over again, with that patient now serving as the index case.

Will contact tracing be the key to easing stay-at-home orders?

However, contact tracing has its shortcomings.

First, contact tracing requires a lot of time and a huge workforce, STAT News reporter Sharon Begley told Vox.

"On average, to identify a person's contacts … takes something like 12 hours of asking, 'Where were you? What were you doing,'" she said. "So it's very time-consuming. … The estimates are that the United States would need at least 100,000 tracers, possibly as many as 300,000."

Contact tracing efforts also would require billions of dollars in funding, according to a report by the Johns Hopkins Center for Health Security. The report estimated that contact tracers typically would be paid about $17 an hour, meaning the cost of paying about 100,000 contact tracers for a year would be more than $3.5 billion.

Carolyn Cannuscio, an associate professor of family medicine and community health at Penn University's Perelman School of Medicine, said volunteers could help lower those costs, but organizations could need government or philanthropic assistance to fund the efforts.

And even if the country has an adequate contact tracing workforce, proper contact tracing relies on human memory and cooperation—which can be flawed.

For instance, some people may forget some of their contacts or, in some cases, a person may not know their effective contacts' names.

How tech companies, public health officials want to fill the gaps

Some tech companies, such as Google and Apple, are developing tracking systems based on smartphone data and applications that potentially could "fill a hole in person-to-person contact tracing" by automatically identifying and notifying contacts who were near index patients—whether the contacts are familiar with the index patient or not, The Verge reports.

But it remains to be seen if users will opt in—and until that technology is released, areas without an adequate number of contact tracers might not have the robust efforts needs to effectively curb the new coronavirus' spread.

But in places where robust contact tracing is possible, health officials are finding that most patients are eager to contribute to the process. "People who are sick don't want others to suffer," said Cannuscio, who is leading a contact tracing effort in Philadelphia. "I think there's probably some healing potential there."

Jeff Engel, senior adviser for COVID-19 to the Council of State and Territorial Epidemiologists, added that even flawed executions of contact tracing will be key to relaxing social distancing measures. "Even the leaky quarantine is effective," he said. "If you get 85% of contacts to self-quarantine for 14 days, you're going to do a lot in the community to decrease transmission."

Frieden expressed a similar view. "Yes, [contact tracing is] really hard. It's not perfect," and "[s]ome cases will be missed, some context will be missed," he said. However, Frieden added, "it can make a big difference, and it can help us get out sooner and safer" (Simmons-Duffin, "Shots," NPR, 4/28; Luthern, Milwaukee Journal Sentinel, 4/25;  Lee, Forbes, 4/17; Pletz/Hill, ABC News, 4/24; Avril, Philadelphia Inquirer, 4/24; Wetsman, The Verge, 4/10; Simmons-Duffin, "Shots," NPR, 4/14; Markus, Vox, 4/24).

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