Shanghai epidemic: Professor Chen Zhengming of Oxford University talks about why the number of infections remains high, and how to understand the ultra-high asymptomatic ratio? – BBC News in Chinese

Second, any test will have false negatives. Especially now, most of them take mixed inspections, 10 people in groups, and centralized analysis. After the mixed test, the amount of virus is diluted, and the test results are not 100% accurate, and may miss a lot (diagnosis). Another reason is that after infection, there is an incubation period. Even in the active period, the virus may appear and disappear from time to time. Sometimes it is caught and sometimes it is not caught. This will affect the accuracy of the inspection and the effectiveness of the clearing measures.

Furthermore, the stock of infection in the Shanghai community itself is already very large, which is more serious than expected. Screening the whole population once or twice cannot solve the problem. Repeated screening and testing within a few weeks is required to find all the infected people.

In addition, there is also a risk of infection in the contact between residents and the outside world. For example, if the sterilization of takeaway express delivery is not done well, it is also possible to (infect the virus). But it needs to be emphasized that although this situation is risky, (contagion) is not very likely.

In addition, the current nucleic acid detection (technology) is designed based on the viral nucleic acid sequence of the initial outbreak in Wuhan, and the sensitivity to Omicron may be affected.

Although the antigen test results are fast, the sensitivity is not high enough. It may not be detected in the early stage of infection, and the virus can only be detected when a certain amount of virus is reached. During this time, the infected person is actually contagious.

BBC Chinese: How do you view the epidemic prevention measures taken by Shanghai?

Chen Zhengming: This time I think the situation in Shanghai is very difficult and the challenges are beyond imagination.

Now that the makeshift hospital is constantly being expanded, I am afraid that it will not be able to quench the thirst in the near future. In Shanghai, where there are 25 million people, if the number of infections cannot be controlled and reaches hundreds of thousands or more, can the makeshift hospitals be able to deal with it? If you can’t deal with it, you have to consider home isolation.

Of course, it is hoped that all patients should be checked and collected, and all of them will be admitted to the makeshift hospital, and the social face will be cleared as soon as possible. This is an ideal situation.

But what if it doesn’t work? Can you ask the scientific team to make model predictions, make predictions based on different parameter settings of the model, and formulate 2-3 sets of different response plans to ensure that you are well prepared and foolproof?

BBC Chinese: According to the data released by the Shanghai Municipal Health Commission on April 8, the proportion of asymptomatic infections in Shanghai exceeded 96%. What do you think of such a high asymptomatic rate?

Chen Zhengming: In this wave of epidemics caused by Omicron, international data show that the proportion of symptomatic and asymptomatic infections is about 20% and 80%.

The data of Changchun and Jilin are in good agreement with international data. But the proportion of people with symptoms in Shanghai is particularly low, with less than 5% of people with symptoms. (I) have no first-hand data, I personally think there may be several reasons:

On the one hand, the immunization rate in Shanghai may be particularly high, and the screening is relatively thorough; on the other hand, due to the nationwide screening, some infected people are still in the incubation period. In addition, there may be an artificial subjective dilution of symptoms at the time of reporting.

BBC Chinese: Shanghai has reported one severe case so far, and no deaths have been reported. In addition, even if the cumulative number of confirmed diagnoses exceeds 200,000, there is no high-risk area in Shanghai so far.

Chen Zhengming: Different from international practice, when China reports the new crown epidemic, it divides the number of people with symptoms and asymptomatic. This can easily lead to misinterpretation and underestimate the severity of the epidemic. For example, Shanghai currently detects more than 20,000 new infections every day, but there are only a few hundred cases of symptoms. If you don’t look carefully, you may have a wrong judgment that the epidemic is not serious.

China’s new crown prevention and control graded control areas are mainly divided according to the number of symptomatic infections, and asymptomatic infections are treated differently, which may make community prevention and control more mobile, and can be managed less deadly. The impact on people’s livelihood Slightly smaller.

However, once the epidemic expands, this classification has little meaning, especially asymptomatic infections are also contagious.

A large number of international data show that 2-3 weeks after the outbreak of the epidemic, the number of hospitalizations due to severe illness will begin to gradually increase, and the apparent increase in the number of deaths will lag another 2-3 weeks. Over time, the number of severe cases and deaths in Shanghai should show an upward trend in the coming weeks.

Of course, China’s classification and standards for new crown cases and deaths are also different from international ones. During the pandemic, for the convenience of statistical caliber, the standard in Europe and the United States is that people who have been infected with the new crown virus 28 days before death are counted as deaths due to the new crown.

Many patients (infected with the new coronavirus) may die, not directly from pneumonia or respiratory failure caused by the new coronavirus; they may have tested positive or had mild symptoms, but died of heart disease or tumor metastasis, etc. are counted as deaths due to COVID-19.

China’s criteria for judging deaths from the new crown may be stricter.

BBC Chinese: Now there is a view that Omikron infection is regarded as a big flu, what do you think?

Chen Zhengming: I think this statement is unscientific.

It’s not a large flu, and it has several characteristics that are different.

First, it is particularly contagious, far exceeding that of influenza; second, it has no seasonality, and influenza has seasonality, which usually occurs in autumn and winter. You can see that the spring flowers are blooming now, including in the southern hemisphere, it is summer, and the Omikron is still spreading.

Third, it is far more harmful than the flu without vaccination. About 8,800 people died in the fifth wave of the epidemic in Hong Kong, which is a good warning.

Only after completing the full course of immunization, especially after the booster shot, can the harm of the virus become very weak. In this case, in general, it is not much different from the flu. Especially for healthy people or young people who are in good health, they can be treated the same as the flu.

In this way, the adjustment of prevention and control measures has created a good window of opportunity.

Asian countries such as Japan and Singapore, which have been strictly controlled in the past two years, as well as Australia’s New Zealand and Australia have all opened up. After the opening, the number of infected people has also increased significantly, but people are not afraid. They feel that the infection is like a cold.

Hong Kong has never been able to truly open up. After this round of the epidemic, yin and yang are mixed, and maybe it will be able to come out of the epidemic completely. I think any country has to face this level and pass it, just depends on the timing and cost of passing the level.

BBC Chinese: The discussion in China is that the distribution of medical resources is uneven, and there is fear of a run on medical resources after the liberalization.

Chen Zhengming: Due to strict control and the deployment of a large number of medical personnel to work on epidemic prevention, medical resources may have been severely run on now. This will inevitably adversely affect the diagnosis and treatment of some other non-new coronavirus diseases. There are more than 7,000 surgeries every day in Shanghai. Some surgeries are delayed for a month or two. However, some acute surgeries, such as acute pancreatitis and stent placement, are life-saving surgeries. Will these surgeries be delayed due to control? How can possible secondary hazards be avoided? We must face it scientifically and find a good balance and a technical path for precise management.

For example, different information can be collected through a centralized telephone service to achieve hierarchical diagnosis and treatment, and to determine whether the seeker needs to be hospitalized or sent to a designated hospital for treatment. Patients admitted to the emergency department can also be treated differently based on the presence or absence of nucleic acid testing and the test results, according to the principle of traffic lights, and timely diagnosis and treatment.

During the epidemic prevention and control period, not only the needs of new crown patients, but also other patients must be considered. A one-size-fits-all approach to epidemic prevention will simplify complex problems, ignore the other, and cause unnecessary secondary medical harm.

BBC Chinese: Many people are afraid of sequelae.

Chen Zhengming: There are indeed sequelae, but many studies now are aimed at the first and second waves of the new coronavirus, and many people were not vaccinated at that time, so they became seriously ill after infection, and some patients could not fully recover.

The sequelae of the new coronavirus are now being studied around the world. The chances of (suffering) sequelae after vaccination are definitely lower. But how many sequelae are there, under what circumstances, how long it lasts, and what happens after infection with Omicron, these questions still lack very scientific data.

（Interview contentedited)