The author of this article: Tuntun
Yesterday, the National Influenza Center of the Chinese Center for Disease Control and Prevention released the weekly report on influenza surveillance for week 52 of 2023.
Surveillance data shows that as of December 31, 2023, the positive rate of influenza virus tests has increased in southern provinces and decreased in northern provinces. The A(H3N2) subtype is the dominant form (i.e., "Influenza A"), and the proportion of B(Victoria) lineage continues to increase (i.e., "Influenza B").
From week 47, the number of infections in the North and South has been quietly rising for 6 consecutive weeks. Among them, the proportion of stream B in the southern provinces increased from 11.6% in week 47 to 26.4% in week 52, and the proportion of stream B in the northern provinces increased from 7.1% in week 47 to 47.3% in week 51.
Source: Influenza Surveillance Weekly
The proportion of B stream is increasing, and some children have not been to school since the National Day
The perception of doctors in the clinic also confirms this trend.
Peng Jie, director of the Center for Intractable Infectious Diseases at Nanfang Hospital of Southern Medical University, said, "During this period, the number of influenza-like patients has increased, and the proportion of influenza B has gradually increased. Influenza A accounted for 90% of influenza-like patients in October, but this proportion is decreasing month by month and may now account for only 60%. Mycoplasma is still predominantly prevalent in children, and influenza is less common, while influenza is predominant in adults. 」
The feeling is even more pronounced in the north.
Li Tong, chief physician of the Department of Respiratory and Infectious Diseases of Beijing You'an Hospital, once said that among the patients with respiratory diseases treated in the past two weeks, the proportion of influenza B has increased significantly, "It is roughly estimated that only 1/4 of influenza A is now, and most of them are influenza B patients. And it is mainly in children and adolescents, and most of them are clusters of infection. 」
Influenza A and influenza B are two different subtypes of influenza that do not have a cross-immune mechanism. This means that even if you have already been infected with influenza A or B, it is still possible to be reinfected with another subtype of influenza virus.
Peng Jie met many patients who repeatedly came to the outpatient clinic for a period of time due to mycoplasma and influenza infection, "There are also some children who are infected with mycoplasma first, adults who are infected with influenza, and children who have weak resistance during illness and are infected with influenza by adults. 」
#A stream just happened to be recruited B stream again# once on Weibo hot search, some schools have more than a dozen classmates in a class who have taken leave due to the flu, and many children have returned to school after a week of leave, and they have not been in class for a few days before they were infected with other pathogens, and they went home with a high fever again, and some parents even said, "The child has not been to school since the National Day".
On social platforms, many people have the same experience
An analysis of the epidemic characteristics of influenza B in mainland China in 2011~2019 showed that the epidemic intensity of influenza B in mainland China was lower than that of influenza A [1].
According to the data of the National Influenza Center, from October 2021 to March 2022, influenza activity in the northern and southern provinces was dominated by the B(Victoria) line, starting in May 2022, the southern provinces once again entered a period of high influenza with the A(H3N2) subtype as the absolute dominant strain, and from mid-February to the end of April 2023, the mainland presented a wave of influenza epidemic season dominated by the A(H1N1)pdm09 subtype. [2]
Li Tong once said, "In the past, one type of pathogen was usually the main pathogen, but this flu season can see that influenza A decreases, followed by influenza B and then rises, and it is relatively rare for two influenza to cross in the same season. 」
"And this year's flu season started in mid-to-early November, more than a month earlier than usual, and as it stands, it could last longer than usual. 」
The hospital increased its schedule, eliminated its lunch break, and extended it to 12 o'clock in the evening
Influenza A and influenza B are both influenza and symptoms are still fever, cough, sore throat, headache, muscle aches, and fatigue, and the onset is acute and rapidly changing, and the patient's body temperature may rise rapidly within a few hours to 24 hours, reaching more than 39°C. Individual feelings may vary among patients, but no significant difference in symptoms between influenza A and influenza B has been observed clinically.
It is generally accepted that the probability of reinfection with influenza B within one year is smaller than that of influenza A, but other pathogens should also be suspected.
Li Tong once explained, "Influenza A mutates faster, there may be epidemics every year, and there is also the possibility of infection with other subtypes, but influenza B is not so variable, and the protection period after infection is relatively longer, and the next time influenza B comes, people who have already been infected are not so susceptible." 」
Source: Visual China
Although the proportion of B stream B has risen rapidly, the number of patients has fallen relatively compared to the peak in November.
"At the beginning of December, the number of patients had dropped to 30% of the peak, and now it has risen slightly, about 50% of the peak. 」
Hospitals have also adjusted their measures accordingly to cope with the increased demand for medical treatment.
In early December, after the peak had passed, Li Tongzeng's hospital had reduced its fever clinic support. After the increase in the number of in-stream B patients, the infectious disease department has now adjusted its schedule, "The number of staff has increased during the peak hours of the afternoon and evening, and the hospital is also continuing to monitor the number of patients. 」
Peng Jie's hospital has increased the opening unit of the fever clinic, and at the same time increased the frequency of shifts during the original rest time, "We have now canceled the lunch break at noon and extended it in the evening, from 8 a.m. to 12 p.m., which is seamlessly linked. 」
Acknowledgments: This article was professionally reviewed by Peng Jie, Director of the Center for Intractable Infectious Diseases, Nanfang Hospital, Southern Medical University, and Li Tongzeng, Chief Physician of the Department of Respiratory and Infectious Diseases, Beijing You'an Hospital
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Image source: Visual China
Resources:
[1] Wang Qing, Zhang Muli, Qin Ying, et al. Seasonality, age characteristics and vaccine matching analysis of influenza B type B in China from 2011 to 2019 [J]. Chinese Journal of Epidemiology, 2020, 41(11): 1813-7.
[2] Technical Guidelines for Influenza Vaccination in China (2023-2024)
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