Recently, Jiangsu announced that influenza has entered the peak of summer epidemic. According to the monitoring data of the National Influenza Center, the overall positive rate of influenza virus testing in southern provinces showed a downward trend, but some provinces were still in the high summer incidence period.
This summer, the flu epidemic in the southern region has attracted attention. In the 14th-30th week of 2022, a total of 804 ILI outbreaks were reported in the southern provinces of the mainland, up from the same period in 2021 (152 cases). According to expert analysis, this is related to the low rate of influenza vaccination in the mainland and the decline in the pre-existing immunity of the population to influenza.
In the context of the ongoing global epidemic of the new crown epidemic, some studies believe that influenza and new crown co-infection or aggravation of the disease. China disease control experts said that this year's mainland influenza vaccine batch was issued relatively early, and it is recommended that all localities make timely preparations for influenza vaccination.
The overall decline in the positive rate of influenza in the south is still in the high incidence period
Recently, the Jiangsu Provincial Center for Disease Control and Prevention released news that the Jiangsu flu has entered the peak of the summer epidemic. Influenza surveillance data from the province shows that in the samples of upper respiratory tract infection cases collected by sentinel hospitals, the positive rate of influenza nucleic acid has increased for 6 consecutive weeks, and the vast majority of influenza positive strains are H3N2 subtypes, and the intensity of influenza activity is expected to remain at a high level in the near future.
According to historical monitoring data, the summer epidemic peak in Jiangsu lasts for about a month, and then the summer peak dominated by H3N2 will gradually decrease, but after entering the winter and spring, about November to December, the intensity of influenza activity will increase again and enter the peak of the winter and spring epidemic.
The latest surveillance data from the National Influenza Center shows that in the 30th week of 2022 (July 25-July 31), the ILI% (percentage of influenza-like cases) reported by the Southern Province Sentinel Hospital was 4.3%, unchanged from the previous week's level (4.3%) and higher than the same period in 2019-2021 (3.5%, 2.7% and 3.3%). The ILI percentage reported by Sentinel Hospitals in the Northern Provinces was 2.2%, higher than the previous week's level (2.1%), unchanged from the same period in 2019 (2.2%), higher than the same period in 2020 (2.0%), and lower than the same period in 2021 (2.4%).
The overall positive rate of influenza virus testing in southern provinces showed a downward trend, and some provinces were still in the summer high incidence period; Influenza activity in the northern provinces is at a low level. The northern and southern provinces are dominated by influenza A (H3N2) influenza viruses. A total of 5 outbreaks of influenza A (H3N2) were reported this week.
The Beijing News reporter saw from the percentage chart of influenza-like cases reported by the sentinel hospital in the southern provinces in 2019-2022 that compared with the past 3 years, the summer influenza epidemic in the southern region this year is more obvious. From week 19 to week 25, the value rose all the way, peaking higher than in previous years, and then gradually declining, but it is still higher than the same period in previous years.
The data shows that in the 14th-30th week of 2022, a total of 804 ILI outbreaks were reported in the southern provinces of the mainland, higher than the number of reported outbreaks in the same period in 2021 (152).
Dong Xiaoping, chief expert of virology of the Chinese Center for Disease Control and Prevention, introduced at the press conference of the Joint Prevention and Control of the State Council that in 2020-2021, the mainland influenza showed a low-level epidemic, which has a certain relationship with relatively strict public health measures against the new crown, and the long-term low-level epidemic has reduced the proportion of naturally infected people, plus the mainland influenza vaccination has been in a relatively low state, and the pre-existing immunity of the population to the influenza virus will definitely decline. There has been a peak in the prevalence of influenza A (H3N2) subtype influenza virus in the south this summer.
He also said that experts have determined that the risk of a higher level of influenza epidemic this autumn and winter is high, which may lead to a superimposed epidemic of influenza and new crown pneumonia in the autumn and winter or winter and spring of this year.
Experts call for vigilance against influenza co-infections
Some experts have called for vigilance against the problem of influenza co-infection with the new crown.
Recently, Shenzhen National Clinical Research Center for Infectious Diseases/Shenzhen Third People's Hospital (The Second Affiliated Hospital of Southern University of Science and Technology) published a paper entitled "Challenges in the Covid-19 Epidemic Era: The Flu That Cannot Be Forgotten" in BioScience Trends.
Several recent large clinical studies have reported COVID-19 and influenza co-infections in Japan, the United States, Australia, Chile, South Africa, Turkey, and the United Kingdom. Some scholars have found that co-infection is significantly associated with mortality in patients. In addition, simultaneous infection with BOTH THE NEW CORONAVIRUS and respiratory viruses greatly increases the probability of invasive mechanical ventilation in patients, predicting that co-infection will lead to a worse prognosis, but the actual situation needs further research support.
The researchers believe that measures to target COVID-19 may reduce population exposure to influenza, which in turn reduces population adaptive immunity to influenza, which could trigger future influenza pandemics. In the near future, co-infection with COVID-19 and influenza could be a thorny issue. Public health agencies around the world should be aware of this situation and prepare in advance, especially for the upcoming flu season. In addition, more effective vaccines and antiviral drugs should be developed, and the relevant scientific publicity for the prevention of COVID-19 and influenza should continue to be updated and strengthened.
According to the official public account of the journal Human Vaccine, an analysis of case surveillance in the northeastern Brazilian state of Sergipe from 15 December 2021 to 14 January 2022 shows that the case fatality rate of CO-infection with influenza A(H3N2) is higher than that of isolated infections.
During this time, 1458 cases of new crown and 1237 cases of influenza were diagnosed locally. The COVID-19 case fatality rate was 0.8% (11 deaths), while the influenza case fatality rate was 3.0% (37 deaths). During this period, a total of 52 (2.2%) cases of CO-infection with SARS-CoV-2 and influenza A(H3N2) viruses were detected, with a median age of 64 years (all 1-99 years). Three deaths were recorded, with a case fatality rate of 5.8% for co-infection.
This year, the mainland influenza vaccine batch was issued earlier, and the public should be vaccinated early
Dong Xiaoping said that in view of the risk of influenza and new crown pneumonia that may occur in the autumn, winter or winter and spring of this year, we have taken a series of combined measures. For example, long-term monitoring of influenza and new crown pneumonia activity level and characteristics, the mainland influenza surveillance ranks in the forefront of the world, sentinel hospitals, monitoring outlets, laboratories rank among the best in the world, can dynamically carry out risk assessment, timely release of early warning information.
In fever clinics, fever patients should be screened and triaged, and influenza and new crown should be identified and diagnosed in a timely manner; Whether it is influenza or new crown, once an epidemic occurs, the local government should take some necessary public health measures in a timely manner according to the risk assessment of the epidemic situation.
In addition, we have actively promoted influenza vaccination, and this year's mainland influenza vaccine batch was issued relatively early, and it is recommended that all localities make timely preparations for influenza vaccination. Autumn and winter are coming soon, and Dong Xiaoping called on the public to do a good job in the prevention and control of respiratory infectious diseases, and to carry out influenza vaccination as soon as possible before the arrival of the flu season, especially for the elderly and medical workers. Once there are flu-like symptoms such as fever, dry cough, fatigue, etc., it is necessary to seek medical treatment in time and do a good job of personal protection, including frequent hand washing, scientific and standardized wearing of masks, regular ventilation, and less gathering.
Related: Continental influenza epidemics present regional differences
According to the Chinese Center for Disease Control and Prevention, there are regional differences in the influenza A epidemic season: the north, which has a latitude of ≥33°, shows a winter epidemic pattern, and january to February is a single annual peak; latitude
The Jiangsu Provincial Center for Disease Control and Prevention introduced in the tip that in the mid-latitude provinces of the mainland, including Jiangsu, the influenza epidemic pattern is usually double-peaked: summer peak and winter and spring peak. There are some differences between the two.
Affected by external environmental meteorological factors, host immunity levels and virus characteristics, the summer peak is composed of H3N2, and the summer peak does not occur every year; Winter-spring peaks occur almost every year (2020-2021 winter-spring due to the new crown pandemic, influenza did not have a winter-spring peak), relative to the summer peak, the dominant strains are relatively more variety, the epidemic intensity is higher, by four subtypes of strains (H1N1, H3N2, Victoria and Yamagata) alternate or co-epidemic.
Influenza summer peak occurs mostly in the hot summer, primary and secondary school students and other susceptible people in the summer, although the intensity of influenza virus activity is high, but the summer peak caused by the number of cluster epidemics is relatively small, which is also one of the reasons why the previous summer peak has not attracted social attention.
Beijing News reporter Dai Xuan
Edited by Chen Jing, proofread by Li Lijun