Highly Contagious 'Stealth Omicron' Surges... Will Confirmed Cases Increase Further?

"Low Fatality Rate but High Transmission... Epidemic Duration May Lengthen"

On the 22nd of last month, when 99,573 new COVID-19 cases were reported, citizens visiting the temporary screening clinic set up at Seoul Station Plaza were waiting to get tested. Photo by Asia Economy

[Asia Economy Reporter Na Ye-eun] The share of the Omicron subvariant BA.2, known to have higher transmissibility than the COVID-19 Omicron variant, has been confirmed to have increased more than tenfold in a month.

Ko Jae-young, spokesperson for the Korea Disease Control and Prevention Agency (KDCA), explained at the Central Disease Control Headquarters briefing on the 2nd that the share of BA.2 is increasing globally and a rising trend is also observed domestically.

BA.2, newly emerged at the end of January, is known to be 1.5 times more infectious than the existing Omicron variant. Although it can be detected by domestic PCR tests, it was initially undetectable by some other countries' testing systems, earning it the nickname "Stealth Omicron."

Spokesperson Ko said, "Based on early data from the World Health Organization (WHO), we are assessing the transmissibility and risk of BA.2," adding, "It has been confirmed that BA.2 exhibits high transmissibility, but there is no difference in severity compared to BA.1, and we are monitoring this. As BA.2 increases domestically, we will closely examine whether it will affect the peak of the outbreak or the number of confirmed cases if it becomes the dominant strain."

However, he added, "Considering that in regions with a high BA.2 share such as Denmark, the outbreak and confirmed cases are decreasing, the increased transmissibility of BA.2 is not expected to have a significant impact on the rise in confirmed cases."

The detection rate of BA.2 in domestic infection cases rose from 1.0% in the first week of last month to 10.3% in the fourth week, and the detection rate in imported cases also increased from 10.8% to 18.4% during the same period. Considering this spread, BA.2 could become the dominant strain accounting for more than 50% of domestic cases by mid-March, and by the end of March, Stealth Omicron could lead the overall outbreak.

Globally, the proportion of BA.2 increased from 18.6% in the first week of last month to about 35% in the third week. BA.2 has already become the dominant strain in countries such as Denmark, China, and India.

Omicron.
Photo by Yonhap News

The current government quarantine policy focuses on severe cases and deaths even if confirmed cases increase somewhat. This is based on the lower fatality rate of the Omicron variant despite its high transmissibility and the high domestic vaccination rate. The government expects confirmed cases to peak in early to mid-month and then decline.

However, the emergence of new variants could pose another challenge to the government's quarantine policy.

Previously, the government anticipated that "herd immunity" would be achievable with the start of vaccinations, but the emergence of the highly transmissible Delta variant prolonged social distancing measures. Later, in November last year, a phased return to normal life was attempted, but the outbreak of the more transmissible Omicron variant led to a return to social distancing.

Professor Kim Yoon of the Department of Medical Management at Seoul National University College of Medicine predicted, "Because the Stealth Omicron variant spreads quickly, by the end of March, 70-80% of all infected individuals could be confirmed cases of Stealth Omicron."

At the online briefing with the press corps on the 2nd, spokesperson Ko evaluated, "There is no difference in severity between BA.2 and BA.1 (the existing Omicron variant)." He also stated, "Considering that countries where BA.2 has already spread are seeing a decline in cases, we judge that the impact of BA.2 will not be significant."

Professor Kim also explained, "In other countries such as Europe and the United States, new variants have typically caused new peaks in outbreaks, but Stealth Omicron is a type of Omicron variant, so it is unlikely to create a new wave."

He added, "Although the fatality rate of Stealth Omicron is not high, its higher transmissibility could raise the peak of the current outbreak or prolong its duration." He continued, "Depending on the scale of confirmed cases, the number of critically ill patients may also increase, so it will be important to determine whether this is a manageable level for us."

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