The changing seasons are always an ideal environment for many types of viruses to thrive, most notably the influenza A and influenza B viruses. This is also the reason why the number of seasonal flu cases has increased rapidly in the community, especially in children and people with weakened immune systems.
seasonal flu is an acute respiratory infection caused by the flu virus, which can spread very quickly and easily in the community. The main route of transmission is through drop shot in the respiratory tract when the patient coughs, sneezes, talks or laughs. The influenza virus can also exist on many surfaces that are touched every day such as door handles, desks, chairs, phones, etc. When a healthy person touches these surfaces and then puts his hand on his eyes, nose or mouth, the virus can invade and cause disease.
In Vietnam, seasonal flu is mainly caused by strains of viruses A/H3N2, A/H1N1 and influenza B. According to the World Health Organization (WHO), each year of seasonal flu can cause 290,000 - 650,000 deaths worldwide and at times up to 20% of the population is infected depending on the type of virus circulating.
Recently, the number of seasonal flu cases, especially influenza A, has increased rapidly in children's hospitals. From the beginning of October to the beginning of November 2025, the National Children's Hospital recorded 3,726 cases of influenza, of which 479 children had to be hospitalized; in the week of October 27 - November 2 alone, there were 1,518 positive cases and 169 hospitalizations with many complications such as pneumonia, mediastinal ear inflammation, and seizures due to fever.
Hanoi Children's Hospital recorded 280 flu-related examinations and 65 hospitalizations in the first week of November, currently treating more than 30 children as inpatients.
The Central Hospital for Tropical Diseases is also treating nearly 50 influenza A patients, mainly young children, many hospitalized cases with bronchitis - congenital pneumonia, high fever, cough, runny nose and fatigue.
MSc. Dr. Nguyen Dinh Dung, Department of Pediatrics, Central Hospital for Tropical Diseases, said: Influenza A is an acute respiratory infectious disease that can occur at any age, but young children, the elderly and people with underlying diseases are susceptible to serious complications. The disease often starts like other respiratory viruses but can progress rapidly, causing pneumonia, respiratory failure or sepsis if not detected and treated promptly. Children with influenza A often have a high fever, runny nose, cough, and fatigue; adults and children often have pain and fatigue. Some children may have shaking, vomiting, diarrhea; if severe, they may show signs of sluggishness, stopping feeding, rapid breathing or chest tightness.
Doctor Dung recommends that parents closely monitor children's health, take their children to the doctor early when there are signs of fever and do not take medicine, especially antibiotics, to avoid complications.
Doctor Truong Huu Khanh, former Head of the Department of Infectious Diseases - Neurology, Children's Hospital 1, analyzed: This year's flu season may affect more people because the influenza A virus circulating is mainly the H3N2 strain, different from previous years when H1N1 was common. H3N2 is assessed to be rapidly changing, easily spreading and often causing more serious diseases, especially in risk groups such as young children, the elderly and people with underlying diseases.
This year's flu season is complicated globally and is considered the most serious in many years. Many Asian countries are recording a sharp increase in the number of influenza cases, especially influenza A/H3N2 strain. The Ministry of Health said that the main causes of the disease are currently A/H3N2, A/H1N1 and influenza B.
H3N2 and H1N1 are two common strains of influenza A that spread rapidly, but H3N2 is more isolated, easily causing serious complications in children and people with weakened immune systems. Although not as strong as strains such as H5N1 or H7N9, H3N2 is still worrying because of its high spread rate, especially when the infection rate increases, contributing to worsening the disease, especially in the elderly.
