The COVID-19 epidemic is still spreading around the world. What worries many people is that the new coronavirus family has become "new" again - the Omicron mutant strains BA.4 and BA.5 are becoming the main epidemic strains in the world. Recently, sporadic epidemics have occurred in some places in my country. By sequencing the viral genes of infected people, BA.4 and BA.5 mutant strains from abroad were discovered.
What is the transmissibility and pathogenicity of new mutant strains including BA.4 and BA.5? Are the existing coronavirus vaccines effective? Can my country's current prevention and control measures cope with it? Gao Xiaodong, a member of the Expert Committee on Infection Prevention and Control in Medical Institutions of the National Health Commission and deputy director of the Infection Management Department of Zhongshan Hospital Affiliated to Fudan University, said in an interview with reporters: In the face of the constant mutation of the virus, there is no need to "panic excessively" like facing a formidable enemy, but neither can Take it lightly. Existing prevention and control measures are still effective, and traditional protective measures such as wearing masks must be implemented.
We must have a correct understanding of the R 0 value of the new coronavirus transmission coefficient
Data show that since December 2021, new coronavirus mutant strains have rapidly spread around the world and have been mutating rapidly. Since the early detection of Omicron B .1.1.529, BA.1, and BA.2. Recently, two new sublineages—BA.4 and BA.5—were discovered through sequencing, and they are rapidly becoming popular in many countries.
So, from BA.1 and BA.2 to BA.4 and BA.5, is it true that the larger the number, the more powerful the communication power? Experts told reporters that BA.5 has more mutations than BA.1, but the size of the number cannot be completely equated with the infectivity of the virus, and further research is needed to confirm it. "Based on the existing evidence, BA.5 has the strongest transmissibility. If the infectivity is measured by the basic reproduction number (R0) of an infectious disease, when people have not acquired immunity, the ancestor strain of the new coronavirus that spread early The R0 value is about 3.3, the R0 value of the Delta variant is about 5.1, the R0 value of Omicron BA.1 is about 9.5, the R0 value of Omicron BA.2 is about 13.3, and the R0 value of BA.4/5 The R0 value may reach 18.6," Gao Xiaodong told reporters.
Dong Xiaoping, chief expert of virology at the Chinese Center for Disease Control and Prevention, also said in a recent interview with the media that compared with previous mutant strains, the transmissibility of the BA.4 and BA.5 mutant strains is significantly enhanced. Specific manifestations include: first, the incubation period is significantly shortened, which means that the infected person can become positive in a shorter period of time and has a stronger ability to spread the virus; second, research from Japan, South Africa and other countries and regions shows that without In the case of interference or little public health intervention, the transmission coefficient R0 value reaches 18, indicating a very high transmission speed. In some European countries and the United States, the BA.5 variant has replaced other Omicron variant branches and become the dominant strain.
Gao Xiaodong emphasized a key detail to reporters, that is, the premise that the R0 value of BA.4/5 may reach 18.6 is "when people have not acquired immunity." The "immunity" here can be understood more as "immunity" Ability", including not wearing a mask, not taking any protection, not maintaining social distance, not having been vaccinated against COVID-19, etc. In other words, when people do not use any protection, the R0 value of BA.4/5 may reach 18.6. "At present, this situation is unlikely in our real life, because most people wear masks and pay attention to protection. This also reminds us once again the importance and necessity of adhering to traditional protection methods and getting the new crown vaccine." Gao Xiaodong explain.
In essence, it is still the Omicron mutant strain, and existing prevention and control methods are still effective.
So, will the BA.5 mutant strain be more harmful to the body? Gao Xiaodong said that based on current observations, compared with other mutant strains of Omicron, the pathogenicity of the BA.4 and BA.5 mutant strains has not been significantly increased or weakened. However, if the BA.4 and BA.5 mutant strains occur on a large scale, they will still be fatal to the elderly with underlying diseases. Therefore, on the basis of the original "three-piece package" and "five more" for epidemic prevention, people are encouraged to actively implement the "new three-piece package" for epidemic prevention - regular nucleic acid testing, vaccination against COVID-19, and proactive scanning of place codes.
“Although BA.4 and BA.5 are branches of the Omicron variant, they are essentially still Omicron mutant strains. From the perspective of transmission mode, droplet transmission is still the main method. Therefore, wear a mask and be diligent. Ways such as washing hands and not gathering together to block the spread of droplets are still very effective and important means of protection.In addition, we can see from our last round of battle against the virus that COVID-19 vaccination is effective in preventing infection, especially in preventing severe and critical illness and even death. Therefore, citizens will still be encouraged to complete the COVID-19 vaccination to give themselves more A layer of protection. " Gao Xiaodong said.
Author: Tang Wenjia
Editor: Shi Wei
Photography: Yuan Jing
