How coronavirus testing and contact tracing work together to quell COVID-19

Checking back to see who’s been in contact with newly identified patients with an infectious disease is a standard technique for containing an epidemic, but experts argue that it’s particularly important for the coronavirus pandemic.

Trevor Bedford, an epidemiologist at Seattle’s Fred Hutchinson Cancer Research Center, explains why — and lays out a relatively straightforward system for doing contact tracing in combination with testing — in a Twitter thread spun out today.

“We need a huge push to increase the speed and scale of contact tracing, but this doesn’t necessarily require ‘digital’ solutions,” Bedford writes.

The solution suggested by Bedford and his colleagues in the NextTrace effort makes use of mobile device data, but as a supplement to the traditional phone-based and in-phone interviews used in contact tracing.

Other projects, including the ones being discussed by Apple and Google, aim to use proximity data and Bluetooth links, but more care has to be taken to preserve personal privacy. In a white paper, NextTrace says its system would be complementary to those other projects.

One big challenge is that the system relies on early and frequent testing for coronavirus. Studies suggest that nearly half of the virus transmission events occur during the first few days after infection, before the onset of symptoms. That means contacts with infected patients should be identified and tested as soon as possible.

“It is not ethical (or expeditious) to tell an individual ‘they may have been exposed to COVID’ without the ability to get them tested,” the NextTrace team says.

Unfortunately, despite assurances from the White House, easy access to testing is still a problem.

“Given the critical role that testing will play in this venture, we will launch this system only in areas with sufficient testing infrastructure to support the testing load,” the NextTrace team says. The plan is to roll out a pilot project in partnership with public health officials in one region, but NextTrace says “we do not yet have a partnership in place that can be discussed publicly.”

Another challenge has to do with how many personnel would be required to do traditional contact tracing.

Jeffrey Duchin, health officer for Public Health – Seattle & King County, told journalists this week that experts have worked out a formula for determining how many contact tracers would be required to track down COVID-19 cases.

Previously: Coronavirus sleuth outlines his ‘Apollo program’ for bringing down the pandemic

“Using those rough estimates, we’ll need several hundred contact tracers in Washington state, probably about a third of those or so in King County,” Duchin said. “In addition to that large number of contact tracers, we’ll need people to work on isolation and quarantine, social support and all the other wrap-around services that people may need.”

That workforce is far beyond what currently exists. For example, Chris Spitters, health officer for the Snohomish Health District, said that he had the equivalent of four to five full-time workers available to do contact tracing, and that it can take an entire day for just one case to be completed.

“I’ll tell you right now, with 30 cases a day being reported, we could not do that intense a level of contact notification and monitoring,” Spitters said. “It’s probably got to be substantially less than that.”

Digital tools could make things easier. “Unfortunately, no one has real experience with these. It’s hard to know what will work. But anything that seems like it may help, and is not going to take away from the tried and true methods that we trust, should be welcomed,” Duchin said.

Anthony L-T Chen, director of health at the Tacoma-Pierce County Health Department, said an all-digital system may not be necessary. “There are some low-tech solutions, like using call centers and lesser-trained people who can do some of the initial contact and tracing before handing off to higher-level skills,” he said. “I think there are lots of solutions. We just need to be innovative.”

Here’s today’s Twitter thread from Fred Hutch’s Trevor Bedford:

More from GeekWire:

• Coronavirus sleuths kick off campaign for digital tracing of COVID-19 contacts

• UW and Microsoft release contact-tracing app, aiming to battle COVID-19 while preserving privacy

• Seattle tech veterans rush to build an app to trace COVID-19 exposure only to run into Apple rejection

• Coronavirus sleuth outlines his ‘Apollo program’ for bringing down the pandemic