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HO CHI MINH CITY, Vietnam – Health officials in Vietnam have confirmed the country’s first human case of H5N1 avian influenza for 2025, detected in an eight-year-old girl who presented with severe neurological symptoms, including encephalitis.
The case, located in the southern province of Tay Ninh, marks a rare instance where the virus primarily impacted the central nervous system rather than the respiratory system, according to a statement from the Ho Chi Minh City Department of Health, translated and published by the infectious disease tracker FluTrackers.
The young patient began experiencing fever, headache, and vomiting on April 11, 2025. After two days at a provincial hospital with no improvement, she was transferred to Children’s Hospital 1 in Ho Chi Minh City on April 13 in a state of sleepiness and confusion. Doctors there diagnosed her with encephalitis, a serious inflammation of the brain.
Samples taken from the girl’s brain and respiratory tract were analyzed at the Hospital for Tropical Diseases. On April 17, tests confirmed she was suffering from cerebrovascular disease and influenza A/H5, specifically detected in the brain samples. Notably, polymerase chain reaction (PCR) tests on her respiratory samples came back negative for H5 bird flu.
The girl is currently reported to be in stable condition, isolated, and receiving respiratory support via a ventilator. Initial investigations revealed that the child had contact with chickens that died in large numbers at her grandmother’s residence approximately two weeks before her symptoms began. She also has a history of a congenital heart defect (ventricular septal defect), which was surgically repaired when she was an infant.
Infectious disease experts highlighted the unusual nature of this case, emphasizing the virus’s impact on the brain instead of the lungs. This mirrors a rare occurrence in Vietnam back in 2004, where two siblings diagnosed with H5N1 developed severe neurologic symptoms without significant respiratory illness, suggesting the virus’s potential scope of illness is broader than commonly understood.
This 2025 case follows a fatal H5 infection reported in December 2024 involving an 18-year-old man from Long An province, who had also been exposed to sick poultry.
According to the US-based Center for Infectious Disease Research & Policy (CIDRAP), it remains unclear which specific H5N1 clade infected the girl. While the 2.3.4.4b clade has been dominant globally, infecting birds, mammals, and occasionally humans since 2022, scientists warned in 2024 about an H5N1 reassortant virus (containing elements of the older 2.3.2.1c clade) circulating in the Greater Mekong region, known to infect both birds and people.
The World Health Organization notes that while avian flu has a high mortality rate in humans (over 50%), the risk to the general public remains low as sustained person-to-person transmission has not been established. Health authorities continue to monitor the situation closely.
Disclaimer: This news article is based on information provided regarding the H5N1 case in Vietnam as reported by health authorities and infectious disease tracking organizations. Medical information and situations can evolve rapidly.
