Both from China... 10%P Difference in Positivity Rates a 'Mystery'

Short-term Foreigners Tested Immediately at Airport
Nationals and Long-term Foreigners Tested Within 24 Hours
Experts Say Many Nationals and Long-term Foreigners May Not Get Tested

[Asia Economy Reporter Byeon Seon-jin] The proportion of confirmed COVID-19 cases among short-term foreign visitors from China and domestic residents/long-term foreign residents differs by more than 10 percentage points, raising concerns that there may be “hidden infections” and gaps in quarantine measures. Short-term foreign visitors must undergo polymerase chain reaction (PCR) testing immediately upon arrival at the airport, which enforces a strong “mandatory” measure, whereas domestic residents and long-term foreign residents are required to get PCR tests at public health centers within 24 hours, a more “voluntary” approach that may have led to some not getting tested at all.

The scene at Incheon Airport on the first day of strengthened quarantine measures for arrivals from China on the 2nd.
[Image source=Yonhap News]

According to the Central Disease Control Headquarters (CDCH) on the 10th, from the 2nd to the 9th, when PCR testing became mandatory for arrivals from China, a total of 9,802 people entered through airports from China. Among them, 2,224 short-term foreign visitors were tested at the Incheon International Airport testing center, with 390 testing positive. The cumulative positivity rate was 17.5%, meaning about 1 in 5 to 6 people tested positive for COVID-19. From the 2nd to the 9th, the total number of confirmed imported cases from China was 893.

In comparison, among 7,578 domestic residents and long-term foreign residents arriving from China, 503 tested positive. The positivity rate was 6.6%, meaning about 1 in 15 people were confirmed positive. Despite having the same point of departure?China?and undergoing the same COVID-19 testing method, the positivity rate difference between short-term foreign visitors and domestic residents/long-term foreign residents was 10.9 percentage points.

"It’s not that the positivity rate is low, but that some may not have been tested at all"

Experts believe that the significantly lower positivity rate among domestic residents and long-term foreign residents arriving from China compared to short-term foreign visitors may be because some did not undergo testing and thus were not included in the confirmed case count.

Professor Kim Woo-joo, an infectious disease specialist at Korea University Guro Hospital, said, “Looking only at the positivity rate, short-term foreign visitors are tested immediately upon airport arrival, while others are tested within 24 hours, so it is possible that viral load decreased over time leading to negative results. However, the difference is still too large.” He added, “At the airport, testing is immediate, so no cases are likely missed, but testing at a nearby public health center within 24 hours is voluntary. We must consider the possibility that some did not get tested at all. Also, PCR testing for domestic residents and long-term foreign residents should be conducted at the airport for more efficient test management.”

There is indeed a high possibility that domestic residents and long-term foreign residents arriving from China did not undergo testing. On the 2nd, arrival information did not appear in the quarantine information system, and the list of arrivals from China was not shared with local public health centers. Because of this, frontline public health center staff had to call each arrival individually to ask if they were subject to testing, but there was no way to verify if domestic residents and long-term foreign residents who were supposed to get PCR tests actually did so. A CDCH overseas entry management team official stated, “Currently, local governments and public health centers nationwide are guiding those who have not been tested to visit and get tested and register their results.”

Gaps in monitoring variants from China that could become a factor in spread

The government has explained that the reason for applying strict quarantine measures to arrivals from China is “to minimize risks amid uncertain circumstances where new variants may emerge and be introduced domestically.” Currently, whole genome sequencing is conducted on all positive samples from arrivals from China to strengthen monitoring of variants that could become factors in domestic spread. However, concerns remain that hidden confirmed cases may continue to pass through the quarantine system. Experts point out, “Although the government is applying scientific quarantine measures such as the integrated quarantine information system to prepare for a pandemic, it will be ineffective if basic principles and protocols are not properly followed.”

This content was produced with the assistance of AI translation services.