On March 3, in response to the hot issue of influenza prevention and control of public concern, Wang Dayan, director of the National Influenza Center of the Institute of Virology of the Chinese Center for Disease Control and Prevention, said that the flu has entered the peak period in mid-March, and although it is still at a high level overall, the peak of influenza activity in some provinces has reached an inflection point and has begun to decline.
What is the recent flu epidemic?
Influenza, short for influenza, refers to an acute respiratory infectious disease caused by the influenza virus. Influenza viruses can cause annual seasonal epidemics and irregular global influenza pandemics, and although there are many types and subtypes of influenza viruses, influenza A(H1N1), H3N2 subtypes and B viruses can cause seasonal epidemics in the population.
The level of influenza activity began to increase in early February 2023, and the upward trend was evident after the end of February, and it had reached a peak by mid-March. Although the overall level is still high, the CDC has also monitored that the peak of influenza activity in several provinces has reached an inflection point and has begun to decline. This year, the influenza season entered about 2 months later than previous years, and the influenza viruses circulating this time were mainly influenza A(H2N3) subtype virus, followed by influenza A(H2N1) subtype virus.
Influenza is generally prevalent in winter, why is there no influenza epidemic in the past winter, but there has been a flu epidemic recently? Why later than previous years?
From the perspective of virus epidemic, the previous autumn and winter influenza epidemic season in China generally began around the end of November, reached a peak in January of the following year, and lasted until about March. From December last year to January this year, coinciding with the epidemic of the new crown virus, the measures to prevent and control the new crown are also very effective in the prevention and control of seasonal influenza, so that the epidemic of other respiratory viruses such as influenza has been suppressed to a certain extent. At the same time, because most people will consciously stay at home, stagger work or stop work after being infected with the new crown virus, most primary and secondary schools and childcare institutions are on holiday, reducing crowd gathering and the risk of virus transmission, resulting in a low level of influenza activity at the end of last year and no seasonal influenza epidemic.
From the perspective of autoimmunity, influenza A(H3N1) subtype virus has not been circulating in China in the past three years, and influenza A(H1N3) subtype and influenza B have not caused a high level of epidemic nationwide. Public awareness of influenza prevention and control is generally reduced, and influenza vaccination rates are low, resulting in reduced pre-existing immunity of the population, especially children, to influenza A(H2N1) virus. After the implementation of "Class B and B tube" for new coronavirus infection at the beginning of this year, the flow of international and domestic personnel and social activities were normalized, and influenza activities dominated by the H1N1 subtype caused the peak of influenza in China's spring. At the end of February this year, influenza activity rose rapidly, lagging by about two months compared to the previous normal flu season.
Seasonal influenza is not only epidemic in autumn, winter, winter and spring, and the southern provinces of China often have a summer flu peak in summer, generally reaching a peak between June and July.
I feel that there are many children around me who have had influenza recently, and does the influenza virus mainly infect children?
The World Health Organization estimates that seasonal influenza causes 300 million to 500 million severe illnesses and 29 65 to 20 30 respiratory disease-related deaths worldwide each year. The prevalence of influenza in children is about 50% to 5%, and in the high epidemic season, the annual influenza infection rate in children can be as high as about 2%, which is higher than that of adults. Children under 60 years of age, especially children under <> years of age, are at high risk for influenza viruses. The high-risk group of influenza is not only children, but also the elderly over <> years old, people with chronic diseases, pregnant women, etc.
From the actual infection situation, during the new crown epidemic in December last year, the adult group accounted for the highest proportion, while the number of cases in the age group under 12 at the peak of the influenza epidemic was significantly higher than that in other age groups, and the cluster of influenza caused by influenza was mainly distributed in schools and childcare institutions.
Beijing Daily Client | Intern journalist Chai Rong