When Eryang strikes, how many people will be affected? Are Sanyang and Siyang still worth worrying about?

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Written by Li Shanshan

1. Eryang is here

On May 22, Zhong Nanshan said at the Greater Bay Area Science Forum that model predictions show that the peak of the second wave of the new crown epidemic this year will be at the end of June, with about 65 million new infections per week.

As early as April 29, according to the weekly "National New Crown Epidemic Weekly Infection Situation" released by the Chinese Center for Disease Control and Prevention, from April 21 to 27, the number of positive new crown nucleic acid tests reported by provinces across the country was 2.5 times that of last week. The test positivity rate on April 27 was 4.4%, a figure more than double that of a week earlier. On May 6, after the May Day holiday, on Saturday, when the epidemic data of the previous week should normally be released, the CDC did not release new data, and then throughout May, there was no update on the "national new coronavirus infection situation".

An insider revealed to Intellectuals that one of the reasons for the suspension of the update is that at present, "the data of different calibers are not very consistent, and the estimates of different teams are quite different."

On May 23, the National Disease Control Administration again commissioned Peking Union Medical College Hospital to conduct a questionnaire survey on new coronavirus infections, which was one of the sources of infection data in December last year. At present, the results of this survey have not been released.

According to data released by the Beijing CDC Weekly, as of May 21, the new crown has ranked first among statutory infectious diseases for four consecutive weeks, and before that, in the 10 weeks from February 21 to April 23, the first place of statutory infectious diseases has been occupied by influenza. According to the Beijing CDC's weekly report, in the first three weeks of May, the number of reports of 14 statutory infectious diseases, mainly new crown and influenza, also climbed, from more than 10,000 to 18,000 to 25,000.

So, what impact will this surging eryang have on the health of infected people? How many people will this two-yang tide affect? Will there be three yang and four yang after the second yang? How should we deal with the future of the new crown flu?

2. How many people will have two yang?

At the end of May, People's Daily Health Client reported the judgment of Li Tongzeng, chief physician of the Department of Infectious Diseases of Beijing You'an Hospital: "We have observed clinically that this round is more inclined to 'Shouyang' to drive 'Eryang', at the beginning about 90% were 'Shouyang' patients, and 'Eryang' was less than 10%, but now the proportion of 'Eryang' is rising..."

"The new wave of infection, or even the 'second yang tide', is not surprising", Lu Mengji of the Institute of Virology at the University of Essen in Germany said: "In Europe, when Omicron just came out, there would basically be a wave every few months. ”

For the domestic "two yang", Lu Mengji analyzed: On the one hand, immunity is declining, from December last year to May this year, after 6 months, the immunity of the population has dropped a lot. On the other hand, there is the influence of strains, in last year's epidemic, the main strain was two sub-strains of BA.5, and now the global strain has become XBB.

In an interview with experts related to the joint prevention and control mechanism by Xinhua News Agency, Chen Cao, a researcher at the Institute of Virology of the Chinese Center for Disease Control and Prevention, revealed that in China, the Omicron XBB series variant accounted for 91.9% of the local cases, and among the imported cases, its proportion reached 95.2%.

If the two yang cannot be avoided, then the final second yang rate will reach has become a matter of greater concern to the public.

Zhang Zuofeng referred to Intellectuals a recent feature on the issue of new crown reinfection published in the journal Nature, which said: "The latest data from different countries indicate that the proportion (of secondary infection) is between 5% and 15%, and this proportion is expected to increase over time."

However, Zhang Zuofeng also mentioned, "The data in the article is based on past data from other countries, but the mainstream strain in China this time is XBB, and whether the infection rate will be higher has yet to be officially released." ”

Jin Dongyan, a professor at the School of Biomedical Sciences at the Li Ka Shing School of Medicine of the University of Hong Kong, explained to Intellectual: The rate of two yang should not be too high, because in a population that has had a large-scale infection, because of the role of herd immunity, "the transmission rate of the new crown is low", and its Rt value, that is, the effective reproduction rate is below 2. "In Hong Kong, since the tsunami, the Rt value has not exceeded 1.5 most of the time. Under the low Rt value, the second yang rate in Hong Kong has been below 20%."

However, the experts interviewed also admitted that because China's December pandemic did not release accurate infection data, and the vaccination situation was different from other countries, it is difficult to directly estimate the data of other countries and regions in the small wave of the epidemic.

3. Are the symptoms of Eryang serious?

The proportion of two yang is a problem, it is related to whether everyone "will encounter two yang", and the health effects caused by secondary infection is another focus of people's concern.

The aforementioned "Nature" review of new crown infection mentioned that it takes an average of about 7 days for the first infected person to clear the virus, and it only takes 5 days for the second infection. In addition, the chances of being severe, critical and dying from secondary infection have also decreased significantly compared to the first infection, but "30% of people who must use a ventilator for the first time with a second infection are hospitalized for reinfection."

However, the article also shows that if the symptoms of the first infection are severe, the second infection will also be serious. As for the impact of secondary infection on long new crowns, the article cites the latest data from the British Office for National Statistics: if the first infection does not encounter long new crowns, secondary infection is still possible, but "the risk of long new crowns will decrease with subsequent infections, and the risk of adults developing long new crowns after one infection is 4%, and the risk is reduced to 2.4% when secondary infection."

Lu Mengji said: "From the experience of Europe, everyone does not have to worry too much. For the vast majority of people, the symptoms of secondary infection will be much milder. Many young adults have mild or even no symptoms, and without testing, they themselves will not even know that they have experienced a secondary infection."

Regarding the harm of Eryang, Jin Dongyan said: "It is characterized by very few severe cases and deaths, and from the current figures in Hong Kong, it is basically at the same level as the flu." ”

Regarding the current situation in the hospital, a respiratory and critical care doctor in a tertiary hospital in Shanghai told Intellectuals that the pressure in the hospital is "much better than the last time, most of them are still mild, and some patients with underlying diseases have worsened their lung symptoms, but there are very few cases where endotracheal intubation and ventilators are required."

A radiologist told Intellectual: "Recently, there have been many fever and doctors, but the symptoms are not serious, most of the patients are just dizzy and coughing, (in his radiology department), almost no white lung has been seen."

For the severity of Eryang's symptoms, the joint prevention and control mechanism of the State Council recently organized experts to respond. In a report by Xinhua News Agency on May 29, Tong Zhaohui, vice president of Beijing Chaoyang Hospital affiliated to Capital Medical University, said that according to the clinical situation, the symptoms of the recent "eryang" population are generally mild, mainly manifested as upper respiratory tract symptoms, less persistent high fever, and patients recover relatively faster. Wang Guiqiang, director of the Department of Infectious Diseases at Peking University First Hospital, said that the symptoms after secondary infection in the general population are generally mild, the course of the disease is shorter, and the time to turn negative is faster, but a small number of patients are still at risk of disease progression.

4. After Eryang, what will the future of the new crown flu look like?

Eryang is coming, then, do the three yang and four yang after the second yang need to worry? In response to the wave of epidemics that followed, is a booster vaccination for all needed?

Lu Mengji told Intellectual: In Europe, "we are actually in the third wave, the fourth wave, the new crown is becoming flu, and everyone is almost used to it." However, he still reminded, "If there is a wave of epidemic in May, the next wave should occur in autumn and winter, although the multiple infections of the new crown are not terrible, we must still be vigilant against the overlapping peaks of the new crown and influenza in autumn and winter, and prepare enough drugs and medical forces." ”

Jin Dongyan pointed to Hong Kong data, arguing that Hong Kong has already experienced a wave of new crown and flu epidemics in May this year, "but the combination of influenza and new crown has not caused a worse impact on the medical system than the seasonal flu in 2014 or 2017." ”

Zhang Zuofeng believes that although the case fatality rate of the new crown Omicron is close to that of influenza, it is still higher than that of influenza. Taking into account the large proportion of infected people, this will lead to an increase in the number of deaths. It is estimated that the main population of this round of new crown small waves is those who were not infected at the end of last year and the beginning of this year. For people with secondary infection, the general symptoms are mild due to the natural immunity of the first infection. But in older or immunocompromised people, and in people who are severely ill in the first infection, symptoms may be worse than in the first infection. Prevention is the most important thing to avoid secondary or multiple infections. For example, wear a mask in places with many people, pay attention to hand washing, do not crowd, and so on. If infected, seek prompt medical attention and, if necessary, early antiviral therapy to reduce the likelihood of severe disease. Our prevention, treatment and population immunity to Covid is helping us fight Covid and reduce damage, so don't be overly nervous and worried."

Zhang also mentioned that the current vaccination strategy in the United States has changed from booster shots to annual routine vaccination of vaccines against the main epidemic strain.

For vaccination, Lu Mengji said that "catch-up" should be aimed at vulnerable groups such as the elderly and immunodeficient, while for most people, the new crown vaccine only needs to be treated like a flu vaccine, and there is no need to deliberately strengthen it.

"The new crown has now changed from a social problem to a purely medical problem, people who need medical treatment go to the hospital, and then doctors treat it, except for this, most other people do not need to think about this matter anymore," Lu Mengji told Intellectual.