This round of flu has finally passed? Optimistic statements seem premature.
In recent days, influenza epidemics in some areas have indeed begun to show signs of abating. For example, in the 10th week (March 6~12) in Beijing, the number of reported cases of statutory infectious diseases in the city reached an extremely staggering 69,705 cases (of which influenza ranked first), far higher than the level of previous years.
After entering last week (week 11), the number of fever outpatients in many hospitals in Beijing has decreased significantly, and the "boom and decline" of the current round of influenza epidemic in Beijing may have begun.
But looking at the whole country, the A stream and the crowd are still in a state of stalemate. Epidemiologists say that the downward trend in some areas does not mean that influenza A is about to die, and there may also be a fluctuation rebound.
The regional characteristics of influenza A epidemic are obvious, and the perception of peaks is not consistent in various places. In the clinic, some cities still have high pressure or even overload in hospital emergency departments.
The latest weekly report (week 10) of the National Influenza Center shows that two weeks ago, the percentage of influenza-like cases in the northern and southern provinces was still high, and the number of influenza-like cases reported in both the southern and northern sentinel hospitals was still higher than the previous week.
Due to the indiscriminate attack of influenza viruses on the whole population, and the fact that people pay more attention to individual health after the epidemic, people's perception of "A flu trick" this year is particularly strong.
On March 10, 2023, citizens of Lianyungang were vaccinated against influenza
Everything is traced - "immunity debt", "retaliatory rebound", "flu vaccine debt", under pressure, a wave of influenza that spreads rapidly and involves a wide range of people arrives.
Several clinicians and epidemiologists have made it clear that the scale of the flu outbreak is significantly larger than in previous years.
But what everyone is more concerned about, when will this flu epidemic end? According to an epidemiological expert, the influenza virus strain in this year's influenza season is still dominated by H1N1, which has not changed significantly from previous strains, so it is estimated that its peak speed will not change significantly compared with the past.
Is the infection peaking? Perception varies from place to place
In some areas, good news of a peak flu is coming from hospitals.
In early March, Hangzhou Children's Hospital received thousands of children with fever every day, and Zhao Wei, deputy director of the outpatient department, was busy until 11 p.m. Recently, Zhao Wei said that since March 13, children with influenza A have gradually decreased, the number of fever clinics has decreased by about 50%, and there are almost no severe children.
In early March, in a tertiary hospital in Zhejiang Province, infectious disease doctors met overnight to discuss how to deal with this wave of influenza; Yesterday, hospital doctors said that the number of outpatient visits has been reduced by about half, and resources such as medicines and beds have become abundant.
In early March, Shanghai Children's Hospital was waiting for almost all its staff to go to the front, and many posts canceled the five-day work system, especially the doctors in the ward often had to work overtime until more than 9 o'clock at night; In recent days, Zhang Ting, director of the digestive infection department, also felt a little relieved, because although the ward was still saturated, the outpatient overload began to ease, and this week everyone can finally strive to return to the normal rhythm of 5 days of work.
"Compared to its peak, the number of children with fever clinics is now only two-thirds of what it was then, and the downward trend has been going on for three or four days. At its peak, children with fever and emergency visits were more than 400 per day. Chao Shuang, deputy director of pediatrics at Tsinghua Chang Gung Hospital in Beijing, also told Eight Points Jianwen.
However, in areas where influenza A was not severe in early March, many patients with influenza A are now pouring in.
There is a phenomenon of peak shifting and "passing the peak" in various places.
At the beginning of the month, the director of the respiratory department of a tertiary hospital in northern Jiangsu Province had not yet clearly felt the arrival of influenza A, and only occasionally received a few cases of influenza A patients.
In the more than half a month since then, the number of patients with influenza A has increased one after another, and he feels that in the past week, influenza A has reached its peak, "the number of respiratory patients in our hospital has increased by about 30~40%, and the outpatient clinic of the East Hospital has increased by about 40~50%." There was cross-infection between patients in the ward, and "there was even a case of high fever in one ward where all three or four people had a high fever." ”
Flu A and the crowd are in a state of stalemate, and the downward trend does not mean that Flu A is about to die, and there may also be a fluctuation rebound.
Wang Yufang, deputy chief physician of pediatrics at Beijing Kyoto Children's Hospital, said that since last week, the number of patients with flu A has slowly decreased, but on Saturdays and Sundays, the number of outpatient visits has soared.
"This week, the daily outpatient volume reached about 2,400, and at its peak, there were 2,600 outpatient visits." "After the flu outbreak, the number of outpatient visits increased by several hundred compared to usual," she explains. In response to the flu outbreak, hospitals have added several night visits and emergency departments to multiple shifts. ”
In fact, there are regional differences in influenza epidemics, and the progress of epidemics varies from place to place, which is the experience of many years.
Yesterday, Wang Dayan, director of the National Influenza Center of the Institute of Virology of the Chinese Center for Disease Control and Prevention, pointed out that the level of influenza activity began to increase in early February 2023, and the upward trend was obvious after the end of February, and it had entered a peak period by mid-March. Although the overall level is still high, several provinces have also been monitored that the peak of influenza activity has reached an inflection point and has begun to decline.
According to the National Influenza Center Weekly Influenza Surveillance Report (Week 10), it can be seen that influenza cases in the north and south are still on the rise, but the upward curve in the northern and southern provinces shows signs of slowing, and the northern provinces are more pronounced.
It should be emphasized that regardless of the north and the south, this year's influenza is at an absolute historical high in recent years.
Source: National Influenza Center Influenza Surveillance Weekly Report (Week 10, 2023)
Source: National Influenza Center Influenza Surveillance Weekly Report (Week 10, 2023)
Although the growth of influenza epidemics has slowed, it will take time to see when it will end.
Although this year's flu came later than in previous years, Wei Sheng, a professor of epidemiology at the School of Public Health and Emergency Management at Southern University of Science and Technology, estimates that the peak rate of this flu will not change significantly compared with the past.
Delayed flu shot
As a seasonal public good, influenza vaccination is often given every autumn and winter to prevent influenza viruses at the turn of the following winter and spring, and few places will last until March.
This spring has begun to pick up, and the flu vaccination period in some places has been extended, and it has not stopped.
Liu Rong, a vaccination doctor at Kyoto Children's Hospital, told Eight Points that in the past, the outpatient clinic opened appointments for influenza vaccination from September of the previous year to the end of the year or January of the following year. But this year, the epidemic of influenza A since February has led to a sudden surge in vaccination intentions, and hospitals have experienced a rare small spike in influenza vaccination before early February and mid-March.
There have even been cases where parents specially booked a flu vaccine for their children who were not vaccinated last year, and as a result, before the vaccination date, the child was infected with influenza A and could not be vaccinated.
To this end, the hospital purchased an additional batch of influenza vaccines, 20 for those over 3 years old, more than a dozen for those under 3 years old, plus less than 40 stocks left over from last year, a total of less than 100 vaccines, all of which were vaccinated by March 15. "There are now the last stocks left, the second dose for children under 3 years old." She said.
Another factor affecting the extension of the vaccination period is the new crown epidemic, which was still very present in the autumn and winter of last year.
A pediatrician learned when he left the clinic that in November last year, it was the time for influenza vaccination, but the result was a lockdown, and many students went home to take online classes before they had time to get vaccinated, worried that going out would increase the risk of new crown infection, and did not vaccinate alone, "so a group of children did not succeed."
This "delay" also exists in nursing homes.
A director of a nursing home in southern provinces said frankly that in the past, the hospital has been vaccinated and educated about influenza vaccine, and the vaccination rate has remained at about 30%, "but last year there was very little, because all the energy was focused on the new crown vaccination, and the body was lacking." The hospital's COVID vaccination rate is 100%.
On the one hand, there is a delayed influenza vaccination period, and on the other hand, there is a two-stage vaccination process, and this difference is particularly pronounced in influenza vaccination in the elderly.
A number of people in charge of nursing institutions told Eight Points that there was no influenza A epidemic in the area, there was no influenza A infection in the nursing home, and there had been no influenza vaccine education or centralized vaccination organization in the past.
"The flu vaccine is a self-funded vaccine, the decision on whether to fight or not rests with the family, the hospital will not interfere, and there is no need to publicize vaccination, so as not to cause panic." A nursing home director in the central province said.
In order to cope with the A flow, the nursing home under Jinxin Fuxing Health Care continued the protective measures of the new crown period, regularly disinfected and ventilated, not only implemented family appointments for visits, but also required the wearing of masks throughout the visit.
In the past two days, perhaps because of the sense of urgency brought about by influenza A infection, a nursing home in Changsha is collecting the wishes of family members, hoping to hurry up to give the elderly flu vaccination before the end of vaccination.
At this point in late March, many community health service centers have run out of flu vaccines, and institutions are unlikely to restock them — because flu vaccines have a shelf life and expire in April — but these nursing homes are still trying to make amends.
Perhaps the flu did not cause large-scale transmission among the elderly, and a considerable number of elderly people still do not know the harm of influenza viruses.
"When the new crown prevention and control was released last year, we launched the new crown care support hotline for the elderly at home for the first time, this time, we also considered whether to add this item to the hotline, but after the statistical willingness, we found that there was really none, but there were still sporadic calls for the elderly about the new crown revival." Wang Yanni, founder of Qingsong Kanghu, said.
A flow under multiple pressures
The flu has come every year, why is the situation so fierce this year?
In the past, children and the elderly were the focus of influenza, but this year, adults are also affected.
This wave is an indiscriminate attack, the former public health expert of the Chinese disease control told Eight Points Jianwen, "All age groups are susceptible to influenza." It's just that some people have been infected with the same strain in the past, and there will be residual antibodies in the body to protect the human body. ”
A respiratory doctor also said that although children and the elderly are susceptible to influenza, the infection rate of adults in this infection is not small. "Because everyone is not immune now."
Where did everyone's immunity go?
Virology expert Chang Rongshan told Eight Points that due to the past three years, the crowd generally wore masks, maintained social distance, and intermittently isolated at home, resulting in the mucosal immune system that is often attacked by various microorganisms in the air under normal conditions and is in a state of alert, which can be vividly called "herd immunity suppression", and the population immunity has generally declined.
In the case of "immune debt", population movements are frequent, crowd gathering is enhanced, and the influenza virus that has been "suppressed" by the new crown virus for a long time has a "retaliatory rebound", and even faintly exceeds the trend of new crown and other epidemics.
"This is a rebound after the relaxation of prevention and control measures in recent years, in addition to influenza, there are also a series of infectious diseases that may appear this rebound." Wei Sheng said. In fact, the Guangdong Provincial Center for Disease Control and Prevention also recently predicted that the incidence of chickenpox and mumps in Guangdong this year will increase compared with last year.
The "immune debt" is not without solutions, and the cliché is that early flu vaccination can greatly reduce the rate of flu infection. A number of public health experts have repeatedly stressed that the influenza vaccine is seasonal, must be vaccinated before the epidemic season every year, and can have a protection period of about half a year, especially the elderly are the focus of vaccination.
However, the mainland's influenza vaccination rate has been low for many years, and the epidemic has further dampened the enthusiasm of the population for influenza vaccination for three years.
According to a paper published in the Chinese Journal of Preventive Medicine in 2022, Zhao Hongting of the Infectious Disease Management Department of the Chinese Disease Control and Prevention Division showed that in 2021~2022, the mainland influenza vaccination rate decreased from 3.16% in 2020~2021 to 2.47%, a year-on-year decrease of 0.69%. In addition, in 2021~2022, the vaccination rate of the vast majority of people in mainland China declined, and the more decreased were other groups such as medical staff, preschool children, and the elderly.
"People have vaccine hesitancy and worry about side effects. At the same time, influenza vaccine belongs to the second type of vaccine, in most cities need to pay for themselves, the price of domestic influenza vaccine is about 100 yuan, the price of imported influenza vaccine is about 200 yuan, is a big cost for the people. "In addition, the public knows very little about the annual influenza epidemic, and the data on influenza deaths released every year are not clear." ”
"Immunization debt", "retaliatory rebound" and "flu debt", under the pressure, a wave of influenza that spreads rapidly and involves a wide range of people has arrived.
According to the data of the weekly influenza report, in the past 10 weeks of 2023 (March 6 ~ March 12), a total of 807 influenza-like cases were reported nationwide. 3119 influenza virus-positive specimens were detected in the southern province and 3732 influenza-positive specimens were detected in the northern province, for a total of 6838 influenza-A positive specimens.
A number of public health experts and clinicians pointed out that because the number of reported influenza patients is less than the actual number of infected people, the number of positive specimens counted does not reflect the true level of influenza, and can only make judgments about epidemic trends.
The director of the respiratory department of a tertiary hospital in northern Jiangsu said that many patients who came to the hospital had symptoms of high fever, but the test results were not necessarily positive for influenza A.
Shen Ling, chief physician of the Department of Respiratory Medicine of Hangzhou First People's Hospital, told Eight Points Jianwen that he encountered a patient with fever symptoms during his visit, and the patient's daughter was infected with influenza A, but the patient's influenza test result was negative. Later, the patient was advised to do another nucleic acid test, and the result became positive.
A number of clinicians explained to Eight Points that factors such as different testing methods and the length of time for sample delivery will affect the test results of Flu A, and the data shown in the report is only the basic situation that has been diagnosed and reported to a considerable part of the system, and the data that has not been counted is the iceberg under the sea surface.
Written by Tang Zhuoya and Tian Wei丨
Yan Yucheng丨Responsible editor
This article was first published on the WeChat public account "Eight Points Jianwen" and may not be reproduced without authorization
![High incidence of influenza! The latest quadrivalent influenza vaccine has been approved for marketing and can be administered from 6 months to 3 years of age[fig]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)