Why are there so many asymptomatic infections? How to prevent them? Zhang Boli's latest response

For several consecutive days, among the newly reported local COVID-19 infections, there have been more asymptomatic cases than confirmed cases. Especially in the past three days, the number of asymptomatic cases has increased significantly.

Why do asymptomatic infections continue to appear in large numbers? Are asymptomatic infections contagious? With more asymptomatic infections, is it more difficult to prevent and control? On March 28, a Science and Technology Daily reporter asked Zhang Boli, an academician of the Chinese Academy of Engineering, about the above questions.

"The large number and high proportion of asymptomatic infections are the obvious characteristics of this round of epidemic." Zhang Boli explained that this characteristic is not only related to the virus itself, but also to timely screening and early detection of infection, and is closely related to vaccination.

Zhang Boli, academician of the Chinese Academy of Engineering and honorary president of Tianjin University of Traditional Chinese Medicine. Photo by Zhang Daozheng

Most people are asymptomatic because of these three reasons

First, it is related to the characteristics of the Omicron variant. "The new coronavirus variant has increased infectivity, and its toxicity has also been relatively weakened." Zhang Boli explained that the clinical manifestation of the weakened toxicity of the virus is that the clinical symptoms will be milder, and many infected people will not show clinical symptoms for a short time after infection.

The results of the mortality analysis of the Omicron variant and Delta variant from other countries showed that the mortality rate decreased during the epidemic of the Omicron variant, indicating that the pathogenicity of the Omicron variant is not as strong as other variants.

"Despite this, we should not take it lightly for those who are asymptomatic." Zhang Boli reminded: First, although they are asymptomatic, they are still contagious and more hidden; secondly, they may be asymptomatic today but have symptoms tomorrow.

"Especially for key groups, such as the elderly, people with underlying diseases, and the weak, obese and heavy smokers, they are at risk of developing the disease and taking a sudden turn for the worse, and need special attention." Zhang Boli said that for general asymptomatic people, the focus is on isolation and observation, and advocates the use of Chinese patent medicine for early intervention. First, to control the occurrence of symptoms, especially to prevent them from turning into common types; second, to promote the early conversion of their nucleic acid tests to negative.

Many people are asymptomatic.

It is also related to early screening and early detection

"After the outbreak, all localities carried out large-scale screening. Due to early detection, many patients did not show symptoms of infection in the early stages of infection," said Zhang Boli.

As the early detection capabilities of various parts of my country are strengthened, the goal of nucleic acid testing in my country is to complete the nucleic acid testing tasks in the designated areas within 24 hours. The latest deployment of nucleic acid screening enables various parts of my country to detect infected people as early as possible in a shorter period of time and control the source of infection. Therefore, compared with the past when people were found to be infected by going to sentinel medical institutions for fever and dry cough, many infected people were found much earlier.

"Another important reason is that our country's residents have been vaccinated on a large scale." Zhang Boli explained that the population's immunity has generally increased, so most people are asymptomatic.

Are asymptomatic infected people contagious? How to prevent it?

"In the early stages of this round of epidemic, after some asymptomatic infections were diagnosed, their close contacts all showed positive nucleic acid tests." Zhang Boli said when analyzing the Jilin epidemic that asymptomatic infections can easily cause hidden transmission of the virus, and when they are discovered, many people have already been infected.

Although asymptomatic infected people have no clinical symptoms, nucleic acid testing can be used to detect the viral nucleic acid in their bodies. They have a certain viral load and are still contagious.

Relevant experts from the State Council’s Joint Prevention and Control Mechanism said that from the perspective of epidemic prevention and control, the existence of asymptomatic infections makes it difficult to detect the epidemic. If a large number of asymptomatic infections are not discovered in time, the epidemic will further spread, increasing the difficulty of controlling the epidemic in a timely manner.

In this regard, Zhang Boli said that rapid and strict epidemiological investigation and tracing work must be carried out. The key is speed, early detection and early isolation.

"This round of Omicron-caused epidemic has been spreading secretly for some time, and there are multiple transmission routes. Therefore, the epidemiological investigation work is arduous and complicated, and needs to be more rigorous and careful. We must not only pay attention to the close contacts, secondary close contacts, and general contacts of the cases, but also consider whether there was a transmission chain in the early stage of the cases, and find asymptomatic infections as much as possible." Zhang Boli said that only by finding all asymptomatic infections in the shortest time and completely blocking community transmission can we achieve social zero as soon as possible.

Source: Science Popularization China WeChat Official Account