Health officials in Vietnam have reported a severe H5N1 avian flu infection in an 8-year-old girl who is experiencing encephalitis symptoms, which appears to mark the country's first human case of 2025.
The girl is from Tay Ninh province, located in southern Vietnam between Phnom Penh and Ho Chi Minh City, according to an April 18 statement from the Ho Chi Minh City Department of Health that was translated and posted by FluTrackers, an infectious disease new message board.
The patient's symptoms, which included fever, headache, and vomiting, began on April 11, and she was initially admitted to a provincial hospital. When her condition didn't improve, she was transferred to Children's Hospital in Ho Chi Minh City on April 13, where she was diagnosed as having encephalitis.
Officials said the girl has an underlying heart condition and had surgery for a ventricular septal defect when she was 2 months old.
Polymerase chain reaction tests on her respiratory samples were negative for H5 avian flu, but her cerebrospinal fluid sample was positive for the virus, with results confirmed by the Pasteur Institute in Ho Chi Minh City.
The patient remains hospitalized on a ventilator with stable vital signs.
An epidemiologic investigation found that, before she got sick, the child had contact with a poultry flock at her grandmother's house that had experienced mass deaths 2 weeks earlier.
Earlier report described meningitis presentation
Officials said H5N1 infections that involve only the central nervous system are rare but have been reported before, such as in 2004 in Vietnam, when clinicians identified H5N1 in the cerebrospinal one of two siblings who died within weeks of each other from severe neurologic symptoms, but without respiratory symptoms, suggesting that the illness spectrum is wider than previously thought.
Vietnam reported its last human H5 case in December 2024, which involved an 18-year-old man from Long An province who was exposed to sick poultry and died from his infection.
It's not clear which H5N1 clade infected the girl, but in 2024 scientists warned of an H5N1 reassortant circulating across the Greater Mekong region that has infected both birds and people. It contains surface proteins of an older H5N1 clade (2.3.2.1c) that has circulated in parts of Asia with a newer clade (2.3.4.4b) that has circulated globally since 2022.
