Coronavirus: Is Anonymity Key to Contact Tracing?

When a large coronavirus cluster was rumored to have begun among gay men partying in Seoul’s most cosmopolitan nightlife district, city health officials opted for anonymity.

Anonymous testing was provided in clinics to counter the discrimination and stigma gay men in South Korea often experience -- which would have created a barrier authorities worried could hamper case-finding. In response, more than 40,000 nightclub visitors and their contacts were tested, helping to arrest a nationwide outbreak that spread to at least 246 people, researchers said in a report last week.

The screening approach and contact tracing were supported by information gleaned from location data from mobile phones, credit card payment history, public transportation records, and closed-circuit television footage.

It’s an example of using available tools to “rapidly and effectively quell what could have been a much larger outbreak,” said Isaac Bogoch, an infectious diseases physician and scientist at the Toronto General Hospital Research Institute in Canada.

“This is the gold standard of how to effectively conduct contact tracing, especially in stigmatized populations,” Bogoch said in a Twitter post.

South Korea has been widely lauded for its success in suppressing the pandemic. From a peak of more than 800 cases a day in February, the country of 52 million people has managed to bring the number of new cases reported daily down to fewer than 100 since the beginning of April.

The infections linked to nightclubs in Seoul’s Itaewon district coincided with the easing of physical distancing rules on April 30. That was also the start of the Golden Week holiday period, which drew people from across the country to the downtown neighborhood, known for its foreigner-friendly clubs and bars and interspersed with upscale restaurants and kebab stalls.

Of 41,612 tests for the coronavirus conducted during the first few weeks of May, 1,627 were on people whose identity remained anonymous, one of which was positive, the researchers said. The idea for anonymous testing came after municipal government officials consulted with sexual-minority groups to discuss ways to encourage testing among gay men.

“Through the lesbian, gay, bisexual, and transgender community, we advertised that screening clinics of public health centers were conducting anonymous testing for Covid-19,” Cho Ryok Kang, a public health officer with the Seoul Metropolitan Government, and colleagues wrote. “We also advertised anonymous testing through mass media.”

The research, which appeared in the U.S. Centers for Disease Control and Prevention’s journal Emerging Infectious Diseases, highlights measures the Korean government had successfully implemented to snuff out outbreaks stemming from one or two highly infectious individuals or “super spreaders.”

“Despite the low incidence of Covid-19 in the post-peak period of the pandemic, super-spreading related to visiting nightclubs in Seoul has the potential to spark a resurgence of cases in South Korea,” the researchers said.

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