When the call came from the local health department in northeast Nebraska, Katie Berger was waiting. She had already gotten a text from the salon where she’d gotten her hair done recently, telling her that one of the stylists had COVID-19. She knew she was at risk.
“They said, ‘We’re calling to inform you that you were exposed to a COVID-19 patient,’ ” Berger says. “It was still pretty scary getting that call, even though I knew it was coming.” The public health official told her to monitor her temperature and watch for possible symptoms until two weeks after the haircut — April 17. Berger’s been staying at home since that call, hoping her quarantine will end uneventfully.
This process is called contact tracing. It’s been a critical tool to control the spread of infectious diseases for decades. Now, public health leaders are calling for communities around the country to ramp up capacity and get ready for a massive contact tracing effort to control the coronavirus.
Here’s a guide to the basics of the process and how it could help society restart after the current wave of coronavirus cases.
Identify and isolate: How to stop infection from spreading
Contact tracing is a process designed to halt the chain of transmission of an infectious pathogen — like the coronavirus — and slow community spread.
When someone tests positive for an infectious disease they become a “case.” Public health workers then reach out to the case, first of all to make sure they have what they need and that they are self-isolating, and then to figure out who they had contact with who may be at risk of infection, too.
“The whole point of this process is to make sure that people who have the virus are separated from those who don’t,” says Josh Michaud, associate director for global health policy at the Kaiser Family Foundation. “That includes the original case, who’s isolating, and the contacts who might be incubating the disease. If you get them to self-quarantine before they are infectious, then you’ve essentially stopped the transmission of that disease from that transmission train. If you do that with enough contacts, then you’ve effectively interrupted community transmission.”
It’s not perfect — a tracer might not be able to reach all the contacts, and those contacts might not all follow the guidance, says Dr. Jeff Engel, senior adviser for COVID-19 to the Council of State and Territorial Epidemiologists. “But even the leaky quarantine is effective,” he says. “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.”
The World Health Organization breaks down the process into three steps: contact identification, contact listing and contact follow-up.
Step 1: Sleuth out all the patients’ contacts
If you’re picturing being put under a spotlight and grilled about where you were and who you were with, put that image aside. It’s not usually so dramatic.
A public health worker will typically call the patient who tests positive and have a straightforward — and hopefully empathetic — conversation, says Engel, requesting that they help the health department piece together a list of their recent contacts.
For a hair stylist who tests positive, that might involve pulling up a list of everyone who had hair appointments while that stylist was at work, as was the case with Berger. But it can get much more complicated than that. One COVID-19 patient described to the LA Times how he had to reach out to at least a dozen contacts after he attended a conference before everything shut down. It can mean going through your social media posts, your emails or your calendar, trying to piece together who you were close to.
“With some cases, there might not be a contact history — maybe they haven’t left their house, maybe they haven’t come in contact or been exposed or have exposed anybody else,” Michaud says. On the other hand, he says, there can be dozens or even hundreds of contacts to follow up with.
Step 2: Reach out and gain trust
After the list is made, public health workers do outreach to those contacts, which can be brief and to the point. Berger says her call with the public health department took just a few minutes: “They just told me to monitor symptoms until April 17.”
The guidance for each contact may also vary depending on how high risk the contact was. If you were very close to a coughing person for an hour, you may be asked to self-quarantine for 14 days. If you were just in the same room as someone who was mildly symptomatic for 20 minutes, you might just be asked to self-monitor for symptoms.
Receiving calls from a government official about your health can be nerve-wracking. Public health officials have learned lessons from contact tracing sexually transmitted diseases such as HIV and syphilis, Engel says, to talk to people in a way that’s not stigmatizing and will encourage people to get on board with the request to self-isolate or share their contacts.
Step 3: Follow-up
Finally there’s follow-up, and some information about what to do next. Berger says she was told that “if anything changes, or if I develop symptoms, to either call them or to call my primary care physician,” she says.
Michaud says if someone who’s in quarantine does develop symptoms, the health department will want to make sure to get them tested.
Contact follow-up can be rigorous in some countries. In South Korea, for instance, MIT Technology Review reports that each person in quarantine is assigned a government case officer who checks in twice a day, and a smartphone app notifies that officer if the contact leaves their quarantine area.
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