Winter is a peak season for respiratory infectious diseases. While influenza infections remained low in most of the northern hemisphere, according to the World Health Organization, some nations such as Japan and the UK are experiencing an early wave of flu cases described as unusually severe.

The Ministry of Health, Labor, and Welfare of Japan reported that that there were 196,900 flu cases from November 17 to 23,  based on data from thousands of designated medical institutions across the country. The country has entered flu season about a month earlier than last year.

Influenza A (H3N2) is currently the most frequently reported flu strain in countries reporting increased activity. Influenza viruses that primarily infect humans are categorized into two main types: A and B. Last season, two Influenza A strains, H1N1 and H3N2, were detected at similar levels, while Influenza B viruses emerged slightly later.

Data from the weekly influenza report by the Chinese Center for Disease Control and Prevention (China CDC) indicates that H3N2 is also the predominant strain circulating in China currently. All pathogens detected so far are known common ones, with no unknown pathogens or new infectious diseases identified.

Wang Dayan, research fellow at the National Institute for Viral Disease Control and Prevention under China CDC, explained that even within the same flu season, the dominant circulating virus can alternate between Influenza A subtypes like H1N1 and H3N2, or Influenza B viruses.

Peng Zhibin, China CDC research fellow, clarified that flu viruses are prone to mutations known as antigenic drift. "It is precisely these minor changes that cause annual seasonal flu epidemics, but the activity remains at seasonal levels and does not necessarily indicate the virus is becoming progressively stronger," she said.

Currently, China has reported a significant increase in influenza cluster outbreaks in childcare facilities and schools. The positivity rate for influenza detection is notably higher in the 5-14 age group compared to others. Experts predict flu activity will continue to rise in the coming months.

Although the flu season is underway, experts emphasize that getting vaccinated now is still beneficial. Individuals with undiagnosed flu-like symptoms (such as fever, cough, sore throat) or those who have recovered from a previous flu infection can still receive the flu vaccine. 

"We do not recommend getting the flu vaccine during the acute phase of infection," Peng noted. "Vaccination should occur after symptoms disappear and one has basically recovered."

Qin Qiang, chief physician at the respiratory center of Beijing Children's Hospital, said that the vaccine provides protective effects as the flu season might be long.

Other preventive measures

Alongside vaccination, maintaining good personal hygiene habits is crucial. If feeling unwell, seek medical attention promptly and follow the doctor's guidance for treatment.

Experts caution that antibiotics are ineffective against viral infections like influenza. The practice of taking antibiotics immediately upon catching a cold is unscientific.

Song Rui, chief physician at Beijing Ditan Hospital, explained, "Colds are mostly caused by viral infections. Management should focus on rest, hydration, and symptomatic treatment. Antibacterial therapy should only be used under a doctor's guidance when a bacterial infection is confirmed."

Flu symptoms in children can differ

Children aged six and above typically have symptoms closer to adults, potentially including pronounced chills, high fever, muscle aches, and fatigue. Children aged two to five often exhibit obvious fever, cough, and sore throat.

Infants under two years old may not show typical flu-like symptoms. Manifestations might include abdominal distension, digestive issues, or decreased activity. Parents should be vigilant if their children show the above symptoms and seek medical attention promptly if necessary.