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At 0-24:00 on March 22, There were 4 new confirmed cases of new coronary pneumonia and 977 asymptomatic infected people in Shanghai. In recent times, the number and proportion of asymptomatic infected people reported daily in Shanghai have attracted attention.
In fact, in this round of the epidemic, there has been an increase in the proportion of asymptomatic infected people across the country.
Why are so many asymptomatic infected people? What new challenges have been brought to the prevention and control of the epidemic? How do we respond?
The virus "weakened"
Why are there more and more asymptomatic infections? One of the big reasons is that the virus is indeed "weakening". At present, the main popularity on the mainland is the sub-variant BA.2 strain of Omi kerong.
In the view of Lin Jing, director of the Department of Pediatrics of the Eighth Affiliated City Hospital of Guangzhou Medical University, one of the reasons for the increase in asymptomatic infection is that the virulence of the Aomi Kerong mutant strain has weakened, mainly invading the upper respiratory tract. There are many people who test positive for nucleic acid, but the symptoms are mild or even no symptoms.
As the Omikejong mutation itself continues to evolve, its propagation power continues to increase.
Maria van Kerkhofer, Technical Director of the World Health Organization's Health Emergencies Project.
Maria van Kerkhofer, technical director of the World Health Organization's health emergency project, recently said that the Ami kerong BA.2 subtype strain is the most transmissible strain known to date.
Wu Zunyou, chief expert in epidemiology of the Chinese Center for Disease Control and Prevention, said that studies have shown that the spread rate of the Omiljung strain BA.1 is 77% faster than that of the Delta strain, and the spread rate of BA.2 is 66% faster than that of BA.1.
More transmissible and less pathogenic, more infected people show asymptomatic or mild symptoms.
Jiao Yahui, director of the Medical Administration Bureau of the National Health Commission. Source: CCTV News
Jiao Yahui, director of the Medical Administration Bureau of the National Health Commission, revealed that as of 24:00 on March 18, the total number of infected people in hospitals nationwide was 29,127. From the perspective of disease, the proportion of mild and asymptomatic infected people has reached more than 95%, and the proportion of severe and critically ill is less than 0.1%.
On March 18, Wu Jinglei, director of the Shanghai Municipal Health Commission, said in an interview that from March 1 to 17, the number of asymptomatic infected people in the current round of the epidemic in Shanghai accounted for about 89% of the sum of the number of confirmed cases and asymptomatic infected people.
It should be emphasized that although the pathogenicity of Omikeron is reduced, low pathogenicity does not mean that it is not pathogenic. Once the virus has invaded the lungs, severe disease can occur. Since the outbreak of the fifth wave of the epidemic in Hong Kong, the number of serious illnesses and deaths cannot be ignored, and we still cannot take Omicron lightly.
We "got stronger"
The rising proportion of asymptomatic infected people may also be related to our "getting stronger".
The first is that the infected population itself has a strong immunity.
Taking Shanghai as an example, the total number of infected people in this round of epidemic is mainly young and middle-aged, the average age is 40.6 years old, the median age is 40 years old, and the proportion of people under 60 years old accounts for 84.5%, with good health, strong physical resistance, and easy to show mild or asymptomatic symptoms after being infected by the virus.
Second, the increase in asymptomatic infected people may be associated with mass population immunization.
"Now the coverage rate of covid-19 vaccination is high, and many people have received a third injection, which has a good effect on the prevention and treatment of severe diseases." Zhao Wei, a professor at the School of Public Health of Southern Medical University, said that after vaccination, the body's immunity is enhanced, even if infected with the new crown virus, many people's symptoms are less obvious, or appear asymptomatic.
Finally, asymptomatic infected people are also associated with early detection and effective management of cases.
There are some "asymptomatic infected people" who are actually in the early stage of symptoms. After the outbreak of the epidemic, epidemic prevention personnel raced against the virus and implemented measures such as rapid screening and rapid detection, so that some early infected people were quickly discovered before they had time to develop symptoms. The more meticulous the circulation and screening work, the higher the probability of "intercepting" the infected person early, and the more timely the control of disease transmission.
For example, in the new "4+977" in Shanghai on March 22, 3 confirmed cases and 886 asymptomatic infected people were found in isolation and control. They are "intercepted" in the early stages of the disease and no longer spread the virus.
In response to the question of why the proportion of asymptomatic infected people reported by Shanghai is so high, Wu Jinglei also gave a similar explanation: the Aomi kerong strain is less invasive to the respiratory tract than other previous strains; large-scale population immunization has produced an effect; Shanghai has found most people without symptoms through rapid screening.
Be earlier, faster, stricter, more realistic
Does the weakening of the virus and the stronger immunity of the population mean that we can let our guard down?
Contrary. In the face of the characteristics of faster spread and stronger concealment of the Omiljung mutant strain, under the general policy of "dynamic zeroing", our prevention and control measures should be earlier, faster, stricter and more solid.
Lin Jing said that asymptomatic infected people can be divided into hidden infections and infected people who are in the incubation period of onset, both of which are contagious. Ning Guang, an academician of the Chinese Academy of Engineering and president of Ruijin Hospital affiliated to jiaotong University School of Medicine, pointed out that to some extent, asymptomatic infected people are more dangerous in spreading, because everyone does not know that he has been infected.
Asymptomatic infected people with strong transmission and strong concealment are active in society, bringing new pressure to prevention and control. How do we respond to this?
Lin Jing believes that the most important thing is to continue to do a good job in the vaccination of the new crown virus vaccine. "Theoretically, vaccination not only reduces hospitalization and severe illness, but also reduces infectivity. Latently infected people who have been vaccinated are less contagious. ”
Second, race against the virus faster, and identify and control asymptomatic infected people hidden in the population through screening earlier. Ning Guang said that although the number of cases in Shanghai is increasing, most of them were found during the control period, although there is transmission, but the transmission route has been broken, "this is a very good thing." ”
Some experts believe that according to the current situation, in order to better prevent and control, reduce the social burden, and reduce the impact on the lives of the people, appropriate adjustments should be considered for the management of asymptomatic infected people.
"Adhere to the social clearance, further increase vaccination rates, including some drugs to treat the new crown have been approved for emergency use." Overall, we have more means to cope with the likely continued increase in asymptomatic infections. Zhao Wei said.
[Reporter] Zhong Zhe, Huang Jinhui, Li Xiuting
【Planner】Zhang Zhe He Yongrong
【Author】 Zhong Zhe; Huang Jinhui; Li Xiuting
Guangdong health headlines