One case of a mutant strain that is of particular concern has been discovered in the country. Is the second round of the epidemic about to begin quietly?

Recently, the Chinese Center for Disease Control and Prevention released the "National Novel Coronavirus Infection Situation", saying that one variant of the virus of key concern was found during monitoring. As soon as the news came out, it quickly became a hot topic.

Image source: Internet screenshot

Since January, the domestic epidemic trend of COVID-19 has declined and is currently in a low epidemic period. Residents' lives are in good order, tourism, catering, cinemas and other industries are doing booming business, and the number of people not wearing masks on the streets is gradually increasing. People's attention to the new coronavirus seems to be gradually fading.

What exactly is the strain that has suddenly attracted attention, and why is it the focus of attention?

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It is reported that the mutant strain is XBB.1.5 , which belongs to the Omicron subtype strain. It has the characteristics of "high transmission" and "high immune escape" and is also the most contagious Omicron subtype variant to date, but there has been no report of an increase in the severity of symptoms. This subtype variant was first discovered in India in August 2022, and then spread rapidly, and soon became the main epidemic strain in countries such as Singapore. According to data released by the US Centers for Disease Control and Prevention on December 30, 2022, 40.5% of new coronavirus infections in the United States that week were caused by this Omicron variant.

The reason why the mutant strains are the focus of attention is that they are more contagious and pathogenic, have caused a certain impact globally, and may have a tendency to expand. Although XBB.1.5 is more contagious, it is only one of the mutant strains that are the focus of attention. Since December 2022, a total of 14 local mutant strains of focus have been found in the country, including 1 XBB.1, 1 XBB.1.5, 5 BQ.1.1, 1 BQ.1.1.17, 4 BQ.1.2 and 2 BQ.1.8. Therefore, XBB.1.5 is only a new mutant strain of focus added during this monitoring period. There is currently no data showing that the mutant strain is showing a trend of spreading in the country.

In fact, more people are paying attention to it because they are worried that it will trigger a second round of infection. Is this the case?

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Disease monitoring data will indicate the possibility of risk, and focusing on it does not necessarily mean that a greater risk will occur. Vaccine injection or infection will provide a certain immune basis, and this protective effect will gradually decrease over time. If you encounter a strain with enhanced infectivity or immune escape, there is theoretically a risk of reinfection. However, whether a large-scale epidemic will occur at the social level depends on the combined effects of the variant's infectivity, pathogenicity, and susceptibility of the population, and none of the three can be missing.

Judging from the current situation, new mutant strains continue to emerge, and their infectivity and immune escape tend to increase, which does put a lot of pressure on the immune system and the population. One of the main ways to actively avoid large-scale infections is to reduce the susceptibility of the population. Some domestic experts said that the new crown epidemic from December 2022 to January 2023 has formed a social immune barrier to a certain extent, and the number of susceptible people is less than 10% of the total population. In this case, it is unlikely that a new pandemic will occur in the short term.

Monitoring data also show that the dominant strains of the current COVID-19 epidemic in China are still BA.5.2 and BF.7. No other dominant variants have been detected, and no new variants that can break through the immune barrier have been found. Data from fever clinics across the country (excluding Hong Kong, Macao and Taiwan) show that the number of patients has fluctuated at a low level since January 23, 2023, reaching 128,000 on February 13, 2023, a decrease of 95.5% from the peak. These data mean that there is currently no second round of infection in China.

After the implementation of "Class B and Class B management" for COVID-19 infection, the monitoring of sentinel points in medical institutions and community populations and the monitoring of mutant strains have been carried out, and relevant institutions have also regularly announced the results of the monitoring. For the public, the key is to have a positive attitude, not panic, not ignore, and insist on self-protection. Vaccination according to the process, washing hands frequently, wearing masks, less gathering, and more ventilation are still effective means to reduce infection!

Author: Zhang Yu, researcher at the Chinese Center for Disease Control and Prevention, doctor of medicine, and master's supervisor

Review | Li Machao, Associate Researcher, Institute of Infectious Diseases, Chinese Center for Disease Control and Prevention

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