More contagious! Where does the locally transmitted BA.5 variant come from?

In recent days, local epidemics have reappeared in many places. In the new outbreaks in Xi'an and Beijing, the viral gene sequencing of the infected people has repeatedly pointed to the more contagious Omicron BA.5.2 branch.

Data map: Big Wild Goose Pagoda. Photo by Zhang Yuan

29 new cases in 4 days,

Xi'an enters "7-day temporary control"

From 0:00 to 24:00 on July 5, Shaanxi reported 1 new local confirmed case and 10 asymptomatic infections, all in Xi'an. According to information released by the Shaanxi Provincial Health Commission, 4 of them tested positive for nucleic acid in community screening, and the rest were discovered during centralized isolation.

Previously, from 0:00 on July 2 to 24:00 on July 4, Xi'an had reported a total of 10 local confirmed cases and 8 asymptomatic infections.

Facing the resurgence of the epidemic, Xi'an announced that the city would implement temporary control measures for 7 days from 0:00 on July 6. Zhang Xuedong, deputy director of the Xi'an Epidemic Prevention and Control Headquarters Office and deputy secretary-general of the municipal government, said that the 7-day temporary control measures are intended to calm society as much as possible, reduce social mobility, quickly identify potential risk sources, and reduce the risk of cross-infection.

"Because the Omicron variant is more contagious and spreads faster, some infected people have no symptoms or atypical symptoms, so the transmission process is more hidden," said Zhang Xuedong.

As of 12:00 on the 6th, there were 9 high-risk areas and 10 medium-risk areas in Xi'an.

Data map: A woman handed her virus sampling tube to medical staff. Photo by Jia Tianyong, a reporter from China News Agency

The BA.5 variant that must be watched out for

One of the important reasons why this wave of epidemic in Xi'an has attracted so much attention is the results of virus sequencing. According to gene sequencing, the strains infected by the positive cases in Xi'an are all the BA.5.2 branch of the Omicron variant.

On the 6th, Beijing's epidemic press conference also introduced that the disease control department conducted genetic sequencing on samples of infections 1 to 3 reported by Beijing on July 5, and the results showed that the viruses all belonged to the BA.5.2 branch of the Omicron variant.

Since December last year, the Omicron variant of the new coronavirus has become the main prevalent strain of the global COVID-19 epidemic. As the Omicron variant continues to evolve, the World Health Organization listed six sub-branches of the Omicron variant as "evolutionary branches of variants of concern under monitoring" on May 18 this year, including four sub-branches of BA.4, BA.5 and BA.2.

In May this year, the "China CDC Weekly (English)" published an online article reporting the details of the first case of infection with the imported Omicron variant BA.5 in my country.

According to the Xi'an epidemic press conference held on the 5th, the prevalent Omicron variant BA.5.2 branch spreads faster than other circulating variants, such as BA.2 that caused a surge in local cases in my country at the beginning of the year. The infected cases have low CT values ​​and are highly contagious. This strain has caused a new round of epidemic peaks worldwide. Therefore, the current epidemic situation in Xi'an is severe and complicated. It cannot be ruled out that new transmission chains will emerge in the future, causing a high risk of secondary community transmission.

At present, BA.4 and BA.5 have become the main epidemic strains in South Africa, Portugal, the United Kingdom, Israel and other countries; recently, there has been an increase in the number of BA.4 and BA.5 infections in many European countries such as France and the Netherlands and the United States.

Wang Wenling, a researcher at the Institute of Viral Disease Prevention and Control of the Chinese Center for Disease Control and Prevention, said on June 28 that the recent outbreak in Macau, China was caused by the BA.5 variant, and the current epidemic strains in various parts of the country are still the Omicron BA.2 sub-branch series. Based on the existing preliminary research results, the transmission and immune escape capabilities of the new coronavirus Omicron variants BA.4 and BA.5 have slightly increased, making prevention and control more difficult, and increasing the pressure on China to prevent imported cases.

Data map: The picture shows a citizen riding past the Xi'an Bell Tower. Photo by Zhang Yuan

Most of the cases in Xi'an are waste recyclers

According to the epidemic press conference held in Xi'an on the 5th, the virus came from abroad, but the source is still unclear. This is because the main place where the epidemic occurred - Shaanxi Chaohui Recycling Resources Trading and Distribution Market (Dafengshang Recycling Art Museum) is the largest recycling resource trading market in Shaanxi Province, involving a wide range of areas and a complex personnel composition.

According to the report from Xi'an, the vast majority of positive infections found so far are related to waste recyclers or their related personnel, and most of the positive infections have a history of contact by working and living together.

In addition, most of the cases that have been discovered are waste recyclers. This occupational group has a wide range of activities and comes into contact with many people. Before the control, the activity trajectories of many cases involved multiple restaurants, supermarkets, residential areas, large trading markets, highway service areas and other places where people gather and have high mobility.

However, the early infected people in this round of epidemic in Xi'an were discovered during routine nucleic acid testing of key personnel who "should be tested as much as possible", and they were basically in an early infection state when they were discovered.

According to the Shaanxi Daily, the Shaanxi Chaohui Recycling Resources Trading and Distribution Market (Dafengshang Recycling Art Museum) has been closed, and 438 people in the market have been controlled, nucleic acid samples have been collected and centralized for isolation, and the market has been fully disinfected. 87 flow survey teams in Xi'an conducted flow surveys on 56 merchants in the market and 19 risk points in Chang'an District, and a total of more than 1,400 close contacts and secondary close contacts were investigated and all were under control.

Source: China News Network

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