'Only 7 Types'... Asymptomatic Cases Increase and Transmission Power Rises, COVID-19 Becomes More Challenging

Impact of Virus Mutation?

Image source=EPA Yonhap News

[Asia Economy Reporter Kim Heung-soon] "(In the past two weeks) when conducting mass testing on contacts of confirmed cases, a considerable number, approximately 30-40%, have been identified as asymptomatic."

"When conducting epidemiological investigations on previously unclassified patients, positive cases have been found among about 5-10 contacts."

Jung Eun-kyung, head of the Central Disease Control Headquarters (CDCH), mentioned these points during a regular briefing on the 9th regarding the recent major trends of COVID-19 spreading mainly in the metropolitan area. This highlights that compared to previous patient occurrence patterns, the proportion of asymptomatic cases and the speed of transmission have increased. According to health authorities, in early June, the proportion of asymptomatic cases among domestic confirmed patients was around 20-30%. Related data also showed that during epidemiological investigations, an average of 3-5 additional transmissions occurred before the confirmed patient's symptoms appeared. These figures have risen in recent confirmed cases. Some speculate that due to mutations of the COVID-19 virus, tracking confirmed cases and responding to the epidemic have become more challenging.

Seven Groups by Type, Evolving to Survive

According to the CDCH, additional analysis of viral genetic sequences detected from 74 specimens of domestically transmitted COVID-19 cases collected between the 24th and 31st of last month confirmed that all genotypes belonged to the GH group. The World Health Organization (WHO) classifies COVID-19 viruses into a total of seven groups?S, V, L, G, GH, GR, and others?based on amino acid changes caused by differences in genetic sequences.

COVID-19, along with Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS), all have spike proteins in the form of protrusions on their surfaces. The key infectious sites among these spikes attach to receptors on intermediate hosts such as wild animals or human cells, causing infectious diseases. Mutations occur when the amino acid composition of the spike proteins changes. These are categorized by type.

Kim Yong-kwan, a wildlife infectious disease expert and researcher at the National Institute of Environmental Research’s Biosafety Research Team, said, "RNA viruses like COVID-19 have a survival instinct to evade the host’s immune system and expand replication and transmission." He added, "In this process, they mutate with various characteristics, making immune responses more complicated." He further noted, "It is difficult to predict and respond to these mutations; after detecting a new virus type, multiple experiments are necessary to trace back and understand its characteristics."

Image source=Yonhap News

Domestic Transmission Types: S→V→G Group Sequence
"Toxicity May Be Weaker, Transmission Possibly Faster"

According to the Global Initiative on Sharing All Influenza Data (GISAID) operated by WHO, at the beginning of this year when COVID-19 started spreading, the L group genotype was predominant in some countries including China, Taiwan, and the Netherlands. Subsequently, the S and V groups appeared, and as the S group spread to Europe and the United States and mutated, the G group expanded. WHO later subdivided the G group into G, GH, and GR based on types.

In South Korea, after the first confirmed case in mid-January, analysis of initial imported cases identified 33 cases as belonging to the S group. From late February to early April, when a cluster infection centered around the Shincheonji Church in Daegu occurred, the V group predominated with 127 cases. From early April in Yecheon, Gyeongbuk, and early May related to confirmed cases from the Itaewon clubs, the GH group has been mostly detected until recently.

Betty Korber, a researcher at the Los Alamos National Laboratory in the United States, and her team published a study in early July in the international journal Cell showing that the cell proliferation amount of the G group virus is 2.6 to 9.3 times higher than other genotypes. Based on this, some suggest that because cell proliferation is active, the G group lineage virus has strong transmissibility and infectivity, but expert opinions on this are divided.

However, there is a possibility that the virus’s toxicity has weakened through mutation. Professor Chun Eun-mi of the Respiratory Medicine Department at Ewha Mokdong Hospital said, "For a virus to continue living inside the host’s body, it must weaken its toxicity." She added, "The COVID-19 virus is evolving into a form more like a common cold coronavirus, which allows reinfection, rather than SARS or MERS."

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