30% more contagious than Omicron! Super mutant coronavirus strain lands in South Korea

◎ Science and Technology Daily reporter Xue Yan

South Korea's Central Epidemic Prevention Headquarters said on May 10 that it is investigating all imported cases of infection with the BA.2.12.1 variant. So far, South Korea has reported a total of 6 cases of infection with the variant, all of which were imported from the United States. South Korean media pointed out that this "super-strong variant of the new coronavirus" has landed in South Korea.

File photo: Pedestrians wearing masks cross the road in Seoul, South Korea. Photo by Xinhua News Agency reporter Wang Yiliang

BA.2.12.1 variant strain is the focus of attention

The first person infected with the BA.2.12.1 variant in South Korea entered the country on April 16 and was confirmed on April 17. The case was a woman in her 50s who had completed three doses of the new crown vaccine and developed symptoms such as sore throat and runny nose after infection. The South Korean epidemic prevention department initially estimated that there were 16 people who were in close contact with the case, and no other confirmed cases were found after investigation.

After that, five more people entered Korea from the United States on April 18, 22, 24, and 28 (two people), and were diagnosed with the BA.2.12.1 variant on the second day of their arrival in Korea. Except for the infected person who entered Korea on the 18th who had only received two doses of the COVID-19 vaccine, the other four people had completed three doses of the COVID-19 vaccine. The Korean epidemic prevention department placed 14 close contacts of the five newly infected people under medical observation, and no infected person was found as of May 10.

The Omicron BA.2.12.1 variant is a variant of the BA.2 subtype strain known as the "invisible Omicron" and was first discovered in the United States in December 2021. The Korean epidemic prevention department cited relevant foreign statistics and pointed out that the BA.2.12.1 variant is 30% more contagious than the existing Omicron strain, and even about 20% more contagious than the fastest-spreading BA.2 subtype strain. The number of infections caused by it in the United States is currently increasing rapidly. However, the Korean epidemic prevention department said that no evidence has been found that it has an impact on the rate of severe illness.

Lee Sang-won, head of the epidemiological investigation and analysis team of the Korea Centers for Disease Control and Prevention, said that from the current perspective, the recombinant variant of the virus in South Korea has not yet become the dominant strain. South Korea is currently most concerned about the increasing number of BA.2.12.1 mutant strains in the United States. At the same time, it is also closely monitoring whether the B4 and B5 mutant strains that appeared in South Africa will flow in.

Several recombinant variants of Omicron have been discovered

As of May 10, six cases of virus recombinant variants have been detected in South Korea, including one case of domestic infection XQ, one case of imported XE, two cases of domestic infection XE, and two cases of domestic infection XM. Park Young-joon (transliteration), head of the epidemiological investigation team of the Central Epidemic Prevention Headquarters of South Korea, said that since South Korea has stopped investigating the infection routes of virus recombinant variants, it is impossible to determine the source of the variants now, but it is certain that there are confirmed cases of continued infection among the co-residents and colleagues of XQ, XE and XM infected people.

Meanwhile, South Korea is still keeping an eye on statistics on domestic COVID-19 reinfections. In South Korea, COVID-19 reinfection refers to a situation where a patient tests positive again 90 days after the first infection with the virus, regardless of whether they have symptoms or not. In late April, the Korea Centers for Disease Control and Prevention said that based on the results of a census of all confirmed patients from January 2020 to April 16 this year, about 55,906 of the 16,130,920 confirmed COVID-19 cases reported in South Korea were reinfections, accounting for about 0.347% of the cumulative confirmed cases. According to the number of infections, 55,841 were secondary infections and the remaining 65 were tertiary infections. Among the reinfection cases, 52 died, with a mortality rate of 0.09%. Including deaths, there were 72 severe cases, with a conversion rate to severe illness of 0.13%. The proportion of reinfection cases in South Korea was about 0.1% as of December 2021, but after January 2022, when Omicron became the main circulating strain, the proportion rose to 0.36%.

Why does the Omicron strain evolve so frequently?

WHO experts said the genetic diversification of Omicron shows that the new coronavirus continues to face natural selection pressure in an attempt to adapt to its host and environment.

The three newly emerged subtypes of Omicron - BA.2.12.1, BA.4 and BA.5 - have strong immune escape capabilities.

Studies have shown that all three strains have the L452 mutation on the spike protein, which allows them to escape the humoral immune barrier established by vaccines or previous infections with other variants of the new coronavirus.

Source: Science and Technology Daily, partly compiled from CCTV.com

Editor: Zhang Shuang

Review: Julie

Final judge: Wang Yu