What’s Contact Tracing and How Can It Fight Covid-19?

(Bloomberg) -- When a forest fire is raging out of control, firefighters are forced to use blunt measures, such as trenches and aerial bombardment, to contain it. But they must also find and extinguish hidden hot spots to make sure the inferno doesn't blaze up again. A pandemic isn't entirely different. Broad lockdowns are a strategy for bringing the novel coronavirus under control. To stamp it out requires a technique that relies on old-fashioned shoe leather, thousands of workers and a high tolerance for boring details: contact tracing.

1. Isn't there an app for that?

Not really, although some mobile phone technologies can help with it. (More on that later.) Contact tracing has been a major public-health tool since the U.S. and U.K. first used it against sexually-transmitted infections in the 1930s. It's grunt work. Trained staffers ask infected people detailed questions about where they've been and who they've met. Everyone considered to be a contact -- a categorization that varies depending on how infectious the disease is -- is then informed and given guidance about what to do. In the case of Covid-19, close contact means living with someone who has the coronavirus or, according to one definition, having been in a closed environment within 2 meters (6.5 feet) of such a person for 15 minutes or more. These contacts are usually then advised to self-quarantine at home for 14 days while watching for symptoms.

2. When is it useful?

When you have enough resources to track cases. The U.S., U.K. and others tried to use contact tracing at the start of their coronavirus outbreaks but gave up in the face of too many cases. They're now hiring armies of contact tracers in an effort to get started again. Other countries, including South Korea, New Zealand and Germany, have used the strategy to good effect throughout their outbreaks.

3. What other diseases has it been used for?

A laundry list of infections, including childhood illnesses such as measles that are on the upswing again thanks to skipped vaccinations. It's used regularly in the World Health Organization's effort to eradicate tuberculosis and to advise people who might not realize they've been exposed to sexually transmitted diseases. It was used against the Ebola virus in Africa and against Middle East respiratory syndrome (MERS), which is also caused by a coronavirus. Contact tracing also was an integral part of the successful fight to eliminate smallpox decades ago.

4. What are the tracing challenges in this crisis?

Speed is a major issue. Between one-third and one-half of transmissions of the new coronavirus may happen before a person is aware that he or she is sick, a University of Oxford research team suggested in a study published in the journal Science. Another is staffing and money. In Wuhan, China, where the outbreak began, some 9,000 specialists worked to track down close contacts of virus patients. The U.S. government is providing $1.3 billion to help pay for a “contact tracing army” for New York, the U.S. state hit hardest by the crisis. Former New York City Mayor Michael Bloomberg, founder and majority owner of Bloomberg LP, the parent company of Bloomberg News, is donating $10.5 million to that effort together with Bloomberg Philanthropies.

5. Can technology help?

Contact-tracing apps can help, if governments are willing to make them mandatory. In South Korea, authorities are using location data from three mobile carriers and transactions from 22 credit-card issuers to decrease the time it takes to track the movements of infected individuals, from one day to just 10 minutes. China asks people to scan a QR code when entering public places such as shopping malls and offices, making it easier for investigators to later trace those who were in a place at around the same time as an infected person. In countries where data privacy is paramount, it's trickier. “Near-universal app usage and near-perfect compliance” would be needed with any voluntary app, the Oxford team said in its study -- meaning that for the U.S. and Europe, apps will probably be just one piece of the contact-tracing puzzle.

The Reference Shelf

• Related QuickTakes on silent spreaders, concerns about a second wave of infections, digital tracing and privacy concerns, the quest for drugs and vaccines, and virus testing.
• The World Health Organization's Q&A on contact tracing.
• The Oxford team's study on digital contact tracing.

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