The AH3N2 flu strain has the ability to spread rapidly and can easily cause serious complications.

NDO - The main influenza A strain currently causing disease is H3N2, a virus strain that can spread quickly and easily cause serious complications in children, the elderly and people with underlying immunodeficiency diseases.

Recently, at the Department of Respiratory Diseases, 108 Central Military Hospital, many people with flu have had severe, even critical, progression. Most of them have underlying diseases and cannot control their underlying diseases well.

Influenza patients with underlying medical conditions often have more severe symptoms than patients of the same age without underlying medical conditions. Therefore, medical staff not only need to treat influenza and its complications: pneumonia, respiratory failure, myocarditis, encephalitis, etc., but also need to control underlying medical conditions well, because influenza infection often causes underlying medical conditions such as COPD, asthma, diabetes, cardiovascular disease, etc. to lose control, leading to an acute exacerbation of the disease.

A typical case is an 83-year-old man in Hanoi with a history of hypertension and type 2 diabetes. He was hospitalized with a persistent high fever of 39-39.5 degrees Celsius, cough, chest pain and difficulty breathing. Despite treatment with antiviral drugs and control of underlying diseases, his pneumonia and respiratory failure continued to worsen, requiring him to be put on a ventilator in the Intensive Care Unit.

Dr. Le Quoc Hung, Head of the Department of Infectious Diseases, Cho Ray Hospital, analyzed that influenza viruses are divided into 3 main groups: Influenza A: The most dangerous type, can spread widely and cause a global pandemic; Influenza B: Only transmitted between people, often less mutated than influenza A but can still cause serious illness; Influenza C: Rare, mild symptoms, almost never causing a large epidemic.

The 2025 flu season is evolving very complicatedly not only in Vietnam but also around the world . In some places, the incidence rate is increasing, in some places the rate of severe patients is increasing.

The Department of Respiratory Diseases, 108 Central Military Hospital has received and treated many severe influenza A patients, most of whom are elderly.

Dr. Le Quoc Hung explained that the suddenly colder weather this winter-spring season creates favorable conditions for the flu virus to survive and thrive. Air pollution caused by fine dust increases, easily causing pneumonia and thus making it easier for the virus to penetrate.

After contact with a sick person for about 1-4 days, the disease usually starts suddenly with symptoms: high fever, muscle aches, fatigue, chills, dry cough, sore throat, stuffy nose, runny nose. In young children, it may be accompanied by vomiting and diarrhea. These symptoms will last about 2-3 days. During this time, the possibility of spreading the disease to others is very high, so it is necessary to pay attention to avoid contact and take all personal hygiene measures to prevent spreading the disease to those around you.

From the 3rd to 5th day after the onset, the symptoms of fever and pain will decrease rapidly, but persistent cough accompanied by chest pain (usually increasing in the evening) and prolonged fatigue. This is a rather sensitive stage because serious complications can occur.

In addition, the social distancing due to Covid-19 lasting more than 2 years has reduced the annual incidence of seasonal flu and also reduced the annual seasonal flu vaccination rate. Both of these factors have caused a sharp decrease in immunity to seasonal flu in the community because antibodies against seasonal flu only last less than 1 year, so if you do not get vaccinated every year or get reinfected, you will no longer have specific antibodies to the flu virus.

"Many cases of secondary influenza infection occur after respiratory infections caused by HMPV, RSV... This explains why some people who have recovered from the flu for a few days then get the flu again," said Dr. Hung.

Dr. Hung noted that the main influenza A strain currently causing disease is H3N2, a virus strain that can spread quickly and easily cause serious complications in children, the elderly and people with underlying immunodeficiency diseases (such as diabetes, chronic kidney failure, chronic bronchitis, etc.).

"All of these factors combined to make this year's flu epidemic more severe and complicated," said Dr. Hung.

Besides influenza virus, there are many other agents that cause acute respiratory tract infections, they can be viruses (not influenza virus) such as RSV, HPMV, Adenovirus, Rhinovirus, Parainfluenza virus... or atypical bacteria. Therefore, it is impossible to determine the virus strain that causes the disease based on the symptoms of the disease.

Doctors advise caution when using flu medicine at home.

According to Dr. Le Quoc Hung, antiviral drugs are only used for people at high risk or with severe disease progression. In particular, each type of antiviral drug usually only works on certain viruses. Therefore, it should only be used when there is a test to determine the strain of virus causing the disease.

"For example, the antiviral drug Oseltamivir (Tamiflu) is only effective against influenza A virus, so if you have acute respiratory tract infection caused by influenza B, C or not influenza virus, it will be completely ineffective. Moreover, this drug does not directly destroy living viruses but only reduces their ability to replicate (in other words, prevents the virus from producing a new generation), so it needs to be used early within the first 48-72 hours from the onset of the disease.

If it is delayed for more than 5 days, the majority of patients do not need to use it anymore because the body has created antibodies to block the virus. Some other antiviral drugs currently on the market also have similar effects on some other selective viral agents. This proves that you should not use antiviral drugs yourself because the benefits are lower than the effectiveness and sometimes you will be disadvantaged by the harmful effects of the drugs," Dr. Hung warned.

Source: https://nhandan.vn/chung-cum-ah3n2-co-kha-nang-lay-lan-nhanh-va-de-gay-bien-chung-nang-post859875.html