(We Chinese in America Media Editor Tang Zhao, February 5, 2022) The sister strain "BA.2" of the diseased subtype of the Omicron variant has been found in the United States, and the transmission power is 1.5 times stronger than that of Omicron. The picture shows a Washington state medical center staff member wearing a gas mask to clean the air at the facility. (Photo from Getty Images)

Scientists are closely tracking the second variant of the Omicron variant (BA.1), BA.2. According to the World Health Organization (WHO), BA.2 patients have been detected in 57 countries; about one-tenth of the gene sequences of patients with new coronary pneumonia uploaded to the Global Initiative for Sharing Influenza Data (Gisaid) are currently infected by BA. 2. The BA.1 strain is still the most important source of infection globally, but BA.2 has become the most important strain in Denmark, India, and South Africa.

1. What is the difference between BA.2 and BA.1?

Two weeks after the discovery of BA.1 by South African medical institutions, three sub-forms were found, namely BA.1, BA.2 and BA.3; less than 400 patients worldwide have been infected with the BA.3 strain so far.

The BA.2 strain has 27 mutations, which are not seen in the BA.1 strain. Public health agencies in Denmark and the United Kingdom noted that these mutations made BA.2 30-34% more infectious than BA.1.

The UK Health and Safety Authority identified BA.2 as a "virus under investigation" in mid-January; the WHO identified Omicron's sub-mutant strains as "variant of concern” but has not yet identified BA.2 alone Variable risk ranking.

2. Can BA.2 avoid immune protection?

The latest Danish study pointed out that BA.2 "has the property of evading immunity"; compared with BA.1, it can "further weaken the protective effect of the vaccine", but the possibility of vaccinated infected persons re-infecting infected persons has not improved. The latest data from the UK Health Security Agency shows that the vaccine is slightly more effective against BA.2 than BA.1.

People at least two weeks after the third dose of the vaccine had 63% protection against symptomatic infection with the BA.1 strain and 70% protection against BA.2. However, this estimate remains uncertain due to limited data. About half of the current South African patients are BA.2 patients.

3. How should BA.2 be treated?

Gupta, professor of clinical microbiology at the University of Cambridge, UK, said that although BA.2 is more infectious, government departments do not need to take stricter epidemic prevention measures against BA.2 than BA.1, because BA.1 is already highly infectious.

Pavlin, a member of the WHO's new coronary pneumonia response team, said that BA.2 will not change the hospital situation in fast-infecting countries, and the number of hospitalized patients has not increased rapidly.

4. How do the currently highly infected countries respond to BA.2?

Patients infected with BA.2 in Denmark account for more than 60% of all new COVID-19 infections, and about 1,100 patients have been hospitalized, the highest number since the outbreak, but about a quarter of them were primarily treated for diseases that were not targeted COVID-19.

The South African government announced this week that people who are "positive" but asymptomatic do not need to self-isolate. Although most of the patients in India are infected with BA.2, Mumbai has eased epidemic prevention measures this week.

In Hong Kong, a traveler infected with BA.2 infected hundreds of people during a three-week hotel quarantine, the most serious infection since the outbreak. Shi Ruiha, a clinical virologist at the University of Hong Kong, pointed out that this shows that the previous epidemic prevention measures may not be effective enough, because BA.2 is more infectious.

5. Could BA.2 become the most dominant strain in the world?

Danish experts pointed out that other countries are also possible, but countries with high vaccination rates will be able to avoid a new wave of hospitalizations and will not prolong the global epidemic for too long.

Stuart, professor of structural biology at Oxford University, said it was not surprising that BA.2 surpassed other strains to become the most dominant strain in the UK.

Olivera, director of the South African Centre for Infectious Disease Response and Innovation, pointed out that focusing on the number of infected people in BA.2 is not the right approach because the hospitalization rate of patients is not high.

(Source: Compiled from Online Information)