3 out of 10 Are 'Invisible Patients'... "Increased Risk of Further Transmission" (Update)

COVID-19 Central Disease Control Headquarters Regular Briefing
"33.2% of New Cases Yesterday Have Unknown Infection Sources"

On the 27th, as the novel coronavirus infection (COVID-19) rapidly spread nationwide and the number of new confirmed cases surged to the 400s, the screening clinic set up at Yeongdeungpo-gu Public Health Center in Seoul was crowded with citizens seeking testing. Photo by Kim Hyun-min kimhyun81@

[Asia Economy Reporter Choi Dae-yeol] As clusters of the novel coronavirus infection (COVID-19) spread across the country, so-called 'unknown transmission patients,' whose links cannot be identified, have significantly increased to account for more than 30% of all confirmed cases. The rise in patients with unclear infection routes indicates that silent transmission is already spreading throughout society, raising concerns about further spread.

At a briefing on the 27th, Kwon Jun-wook, Deputy Director of the Central Disease Control Headquarters, stated, "As of today, 33.2% of the new confirmed cases are patients whose infection routes are under investigation," adding, "Anyone who has been exposed to a risky situation or has even slight suspicious symptoms should get tested."

The health authorities conduct epidemiological investigations to determine where infections occurred once new patients are identified. While many patients belong to already identified clusters, new clusters with untraceable links are emerging nationwide due to the recent spread. When new patients or cluster outbreaks are confirmed but infection links are not identified during initial investigations, they are classified as 'under investigation' patients. Since unknown transmission patients increase the burden on epidemiological investigations, the rising proportion is a concern for the health authorities.

On average over the past two weeks, the proportion of such unknown transmission patients stands at 19.4% (764 people). Considering that one of the social distancing level 1 indicators is to maintain the proportion of unknown transmission patients within 5%, this is not a low figure.

Deputy Director Kwon emphasized, "It is true that the proportion of unknown transmission patients decreases as epidemiological investigations are completed or tracing is done," but added, "There are cases where secondary transmissions or more occur during the investigation of unclassified cases, so the fact that the proportion exceeded 30% even for a single day is a very serious situation."

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