The symptoms of "Eryang" are generally mild, why can't we relax our vigilance?

Are the symptoms of "Eryang" mild? Is strep throat all over the country? Should "go to work with illness"? Related topics have frequently appeared at the top of social platforms for several days.

On May 5, Zhong Nanshan, a recipient of the Order of the Republic and an academician of the Chinese Academy of Engineering, said at the 22 Greater Bay Area Science Forum that according to forecasting models, the wave of new coronavirus infections peaked in mid-April, peaked at about 2023 million people per week by the end of May, and peaked at about 4 million people per week by the end of June.

Compared with the first infection with the new crown virus, most of the people infected with the second time feel that the symptoms are milder, what is the scientific rationale for this? Does the mild symptoms of "Eryang" mean that the XBB variant has decreased virulence? Can we let our guard down? Reporters spoke to experts to answer questions.

●Nanfang Daily reporter Zhong Zhe, Zhu Xiaofeng, Huang Jinhui

Why do most people have mild symptoms of "two yang"?

Is it true that most people with second infections feel milder symptoms?

Lin Bingliang, director of the Department of Infectious Diseases of the Third Affiliated Hospital of Sun Yat-sen University, introduced that according to the dynamic monitoring of antibodies of medical staff by the Zhongshan Third Hospital, the antibody titers in the body of people infected with the new coronavirus in December last year are slowly decenuating, which can be commonly understood as the concentration of antibodies is declining.

People with recent "two yang" still have neutralizing antibodies (corresponding antibodies produced when pathogenic microorganisms invade the body), although not enough to completely resist infection, but generally speaking, the symptoms will be milder than the last infection.

"If the human body is compared to a planet, the virus is an invader." Li Feng, deputy director of the Institute of Infectious Diseases of the Eighth Affiliated Hospital of Guangzhou Medical University, said, "The human body encounters an invader for the first time, because it does not know anything about the harm of the virus, for the sake of insurance, it will mobilize more defensive forces to fight it, often overstressed, resulting in high fever, body pain, etc." ”

At the time of the second infection, the "human planet" already knew the invader of the new crown virus, and with the last combat experience (immune memory), the "weapon" produced was more accurate, and there was no need to mobilize the "resources" of the whole body to "bombard" the virus, avoiding the occurrence of non-specific immune storms, showing milder symptoms.

The "immune ammunition depot" of the "human planet" also has a certain capacity, and after the recovery of the new crown virus infection, the reserves of "antibody weapons" will decline rapidly over time, while the decline of cellular immunity will be slower.

Cellular immunity has the ability to cross-protect against mutating virus strains. "Even if the enemy changes his clothes and invades the 'human planet', cellular immunity can still quickly recognize, quickly exert killing ability in a targeted manner, and eliminate virus-infected cells, which will not cause greater damage, and the clinical symptoms will become lighter and shorter." Li Feng said.

Not only the new coronavirus, but also other viruses circulating in the population have a similar phenomenon.

However, several experts also mentioned that it cannot be ruled out that there are some cases of "two yang" after the same severe symptoms, "even ordinary healthy people have such a possibility." Moreover, symptoms are a relatively subjective criterion, and some people have a high degree of tolerance and feel good about themselves, but from the radiological point of view, they may have reached the point where they need to be treated.

Has the XBB variant weakened?

Many people are curious, from the Omicron BA.5.2 variant to the XBB1.9.1 variant, is the pathogenicity of the virus itself weakening?

Lin Bingliang believes that the currently circulating new coronavirus XBB variant and the BA.5.2 and BF.7 variants circulating at the end of last year have no new intergenerational variants, and the symptoms of patients infected for the first time are not much different from last year. "Clinically, including laryngitis, symptoms of new crown infection such as body aches, fever, nasal congestion, and cough may occur, and everyone's symptoms may be somewhat different."

Chen Cao, a researcher at the Institute of Virology of the Chinese Center for Disease Control and Prevention, said that among the local cases collected in China from May 5 to 15, XBB series variants accounted for 21.91%, but their pathogenicity did not change significantly. Surveillance data also showed no significant change in the virulence of the XBB variant compared to the early circulating Omicron subclade.

Whether the XBB variant becomes less virulent may need more research to support it, but it is an indisputable fact that it is more transmissible than previous virus strains.

On May 5, Zhong Nanshan said at a meeting that the mainstream new coronavirus strain currently circulating in Guangzhou is the XBB15.1.9 variant, and in some other places it is the XBB.1.1 and XBB.16.1 variants. A week later, he revealed at the 5 Greater Bay Area Science Forum that studies have shown that the R2023 value of the XBB.1.5 variant has exceeded 0, that is, one infected person can infect more than 30 people.

The increase in the transmission of the virus, coupled with the gradual resumption of social activities after "Class B tube", the occasional mentions of "going to work with illness" and "traveling with illness", experts have negative opinions on this.

Lin Bingliang believes that as an acute infectious disease, the new crown virus infection is highly contagious, and it may be transmitted to colleagues when you go to work with illness, and overwork during the infection is not conducive to physical recovery.

However, because the immune barrier in the population has been established, and drugs and medical care are better accessible, there will be no run on medical resources, so several experts agree that there is no need to worry too much about possible peaks of infection.

Is it still necessary to get vaccinated?

Recently, the Department of Infectious Diseases of Zhongshan Third Hospital admitted 2 patients with severe new coronavirus infection, both of whom were elderly people with underlying diseases.

Although for most young people, "Eryang" will not cause much harm to the body, but for people with underlying diseases, the elderly and immunologically vulnerable people, each infection may develop into a severe case, which should not be taken lightly.

According to the latest research of Zhong Nanshan's team on patients with severe new coronavirus infection, more than half of the imaging manifestations of severe patients are not severe pneumonia, and the impact of the virus on circulatory, neurological, renal and other systems is also very large.

"Inflammatory factors released by the body's immune response after infection with the virus may aggravate the underlying disease. In addition to actively treating new crown infections, 70%-80% of the treatment team's energy is focused on treating patients' underlying diseases. Lin Bingliang said that the medical system now has relatively rich experience and sufficient drugs, which can intervene as early as possible for critically ill patients and identify patients at risk of severe disease in time.

What to do? Zhong Nanshan reminded that key groups should be vaccinated in time with vaccines that can cover XBB variants to actively prevent infection.

WHO's Technical Advisory Group on Vaccine Composition said on May 5 that it recommended that this year's booster shots of the new crown vaccine only target the XBB variant, and that new crown vaccine preparations should produce antibody responses to XBB.18.1 or XBB.5.1 variants, and "other vaccine preparations or vaccine formulation development platforms that achieve neutralizing antibody responses against XBB lineages can also be considered."

The development of vaccines that can cover XBB variants, China's science and technology enterprises are at the forefront of the world. On May 5, Zhong Nanshan revealed at the meeting that two vaccines that can cover XBB are close to being launched. Four days later, on May 22, Wei Yuquan, academician of the Chinese Academy of Sciences and chairman of Guangzhou Wesker, revealed that the trivalent recombinant protein vaccine against the newly circulating XBB variant has been approved by the State Food and Drug Administration for clinical trials and is commercially produced in Huangpu, Guangzhou.

Experts believe that the upcoming vaccine is expected to have a better effect on preventing infection and preventing severe disease. Among the vaccines currently available, nasal spray and inhaled new crown vaccines may be more effective. "Whether the virus can spread, the level of mucosal antibodies is very important, if the mucosal antibodies are relatively high, the virus is not easy to enter the human body, which can play a role in preventing infection." Li Feng said.

Curator: Lv Hong Bian Delong