Shanghai added 4,381 asymptomatic cases in a single day. Zhang Boli explained in detail: Why are there a large number of asymptomatic infections?

On March 27, the Shanghai Health and Health Commission issued the "Notice on Doing a Good Job in a New Round of Nucleic Acid Screening in the City", informing that "a new round of dicing and grid nucleic acid screening will be carried out across the city

From 5:00 on March 28, Pudong, Punan and adjacent areas (including the whole area of ​​Pudong New Area, the whole area of ​​Fengxian District, the whole area of ​​Jinshan District, the whole area of ​​Chongming District, Pujin Street and Pujiang Town of Minhang District, and Xinbang Town of Songjiang District.

On the day of the release of regional and batch nucleic acid screening, there were 50 new confirmed cases and 3,450 asymptomatic infections in Shanghai

From the 13th to the 27th, the number of infected people in Shanghai continued for several days.

Why do asymptomatic infections continue to appear in large numbers? Are asymptomatic infected persons contagious? Is it more difficult to prevent and control the increase in asymptomatic infections? On March 28, the reporter asked Zhang Boli, an academician of the Chinese Academy of Engineering, on the above-mentioned issues

"The large number and high proportion of asymptomatic infections are the obvious characteristics of this round of epidemics

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Asymptomatic people are mostly because of these three points

First of all, it is related to the characteristics of the Omicron variant

The results of case fatality analysis of Omicron mutants and delta mutants from other countries showed that the case fatality rate decreased during the epidemic period of Omicron mutants, indicating that Omicron mutants were less pathogenic than other mutants.

"Nevertheless, asymptomatic people should not be taken lightly

"Especially for key groups, such as the elderly, people with underlying diseases, as well as frail, obese, and heavy smokers, they are at risk of developing and rapidly deteriorating, and they need to pay special attention

There are many asymptomatic people, which is also related to early screening and early detection

"After the outbreak of the epidemic, extensive screening was carried out in various places.

With the strengthening of early detection capabilities in various parts of China, the goal of nucleic acid detection in China is to complete the task of nucleic acid detection in the designated area within 24 hours

"Another important reason is that Chinese residents have been vaccinated on a large scale

Are asymptomatic infected people contagious? How to prevent?

"In the early stage of this round of the epidemic, after some asymptomatic infections were diagnosed, there were cases where their close contacts all showed positive nucleic acid

Although asymptomatic infected people have no clinical symptoms, they can detect the nucleic acid with virus in their body through nucleic acid detection.
They have a certain viral load and are also infectious
.

Relevant experts of the joint prevention and control mechanism of the State Council said that from the perspective of epidemic prevention and control, the existence of asymptomatic infections makes it difficult to detect the epidemic, and if a large number of asymptomatic infections are not detected in time, the epidemic will further spread.
It has also increased the difficulty of controlling the epidemic in a timely manner
.

In this regard, Zhang Boli said that it is necessary to carry out rapid and strict traceability of the flow adjustment.
The key is to be fast, early detection and early isolation
.

"The epidemic caused by this round of Omicron has been spreading for a period of time, and there are multiple routes of infection.
Therefore, the flow adjustment is difficult and complicated, and it needs to be more strict and careful, not only to pay attention to the close contact, sub-close contact, and general contacts of cases, but also to It is necessary to consider whether there is a transmission chain in the early stage of the case, and try to find asymptomatic infected persons as much as possible
.
" Zhang Boli said that only by finding all asymptomatic infected persons in the shortest time and completely blocking community transmission can the social face be cleared as soon as possible
.