A study by the Central Institute of Hygiene and Epidemiology reveals that compared to its initial appearance in Vietnam, the H5N1 virus has undergone slight genetic and pathogenic changes. Over the past year, its virulence gene has decreased from 99.1% to 98.2%.
Dr. Nguyen Thuy Hoa, Head of the Epidemiology Department at the Central Institute of Hygiene and Epidemiology, stated that with these changes, the virus may have adapted better to the human body, resulting in an increase in the number of infections (particularly among asymptomatic individuals), milder clinical presentations, and lower mortality rates.
Surveys also indicate that H5N1 influenza affects all age groups, with the youngest case being 4 months old and the oldest at 81 years. However, the outbreak is concentrated among those under 40, peaking in the 10-19 age group. The mortality rate in each age group corresponds with the number of cases. In Northern Vietnam, the mortality rate is significantly lower compared to the South (38.1% versus 83.3%).
Dr. Nguyen Tran Hien, Director of the Central Institute of Hygiene and Epidemiology, mentioned that the agency continues to collect samples for testing. The national influenza surveillance program has been implemented in Hanoi, Thai Binh, Nha Trang, Buon Ma Thuot, and Ho Chi Minh City since February, involving the collection of samples from influenza patients for testing. To date, thousands of samples have been sent to laboratories at the Institute and regional Pasteur institutes to detect H5N1 infections and study the virus’s mutations.
