Vietnam: Eight-year-old girl diagnosed with H5N1 avian flu accompanied by encephalitis

Second such case in Vietnam since 2004; the virus has impacted the central nervous system as against the known respiratory tract
Vietnam: Eight-year-old girl diagnosed with H5N1 avian flu with encephalitis
According to the World Health Organization, avian flu has a mortality rate over 50 per cent in human beings. Photograph: iStock
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Vietnam has reported its first case of bird flu in 2025 infecting an eight-year-old girl exhibiting encephalitis symptoms.

In December 2024, the country reported an H5 infection in an 18-year-old man belonging to Long An province who was infected after exposure to sick poultry. The person had succumbed to the infection.

According to the US-based Center for Infectious Disease Research & Policy (CIDRAP), the girl is a resident of Tay Ninh province, located in south Vietnam, as per a statement issued by Ho Chi Minh City Department of Health. 

The statement was translated and published by FluTrackers, a dashboard which updates infectious diseases.  

Tracking H5N1 infection

As per the dashboard, the patient complained of fever, headache and vomiting multiple times starting April 11 and was admitted to provincial hospital for two days for treatment with no improvement in her health. 

On April 13, the girl was shifted to Children’s Hospital 1 in a state of sleepiness and confusion  and was eventually diagnosed with encephalitis, an inflammation in the brain caused due to the infection. 

The hospital took samples from her brain and respiratory tract that were analysed at the Hospital for Tropical Diseases. On April 17, the reports confirmed the girl was suffering from cerebrovascular disease and influenza A/H5.

However, she was diagnosed negative for H5 bird flu in polymerase chain reaction tests on her respiratory samples.The patient is currently stable and isolated with assisted breathing via ventilator. 

“Initial information recorded that the child had contact with chickens that died in large numbers at her grandmother's house two weeks ago. The patient is the second child in the family, has a history of congenital heart disease (ventricular septal defect) and had surgery at Children's Hospital 1 when she was two months old,” the statement read.

The statement further said that as per infectious disease experts, the condition is a rare case in which the virus has impacted the central nervous system, instead of the respiratory tract. 

In 2004, Vietnam reported an H5N1 case where the central nervous system was impacted in one of two siblings diagnosed with the disease and died within weeks from severe neurologic symptoms. They did not report any respiratory symptoms, indicating that the scope of illness is wider than previously known. 

The CIDRAP stated that at present it is unknown as to which clade of H5N1 infected the girl. At present, the clade 2.3.4.4b has been widely circulating around the globe and infecting mammals, wild birds, poultry and humans since 2022. 

However, 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), it added.

According to the World Health Organization, avian flu has a mortality rate over 50 per cent in human beings. The virus risk continues to remain low as no known transmission of person to person is reported. 

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