Viet Nam Department of Animal Health (DAH), and the Food and Agriculture Organization of the United Nations (FAO) urge the public to keep vigilance on the Highly Pathogenic Avian Influenza (HPAI) A(H5N1) upon the detection of new re- assorted HPAI A(H5N1) viruses in chickens and muscovy ducks through active surveillance in Viet Nam.

There has been dominance of influenza A(H5N1) clade 2.3.4.4b virus circulation around the world since 2021. Avian influenza A - H5N2, H5N4, H5N5, H5N6 and H5N8 subtypes have all been sporadically detected in poultry or wild birds. From December 2023 to February 2024, at least 646 HPAI outbreaks have been reported in five geographic regions caused mainly by A(H5N1) (610). In Asia, several clades continue to circulate, including A(H5N1) 2.3.4.4b, 2.3.2.1c and others, which can lead to reassortment and the appearance of viruses with new characteristics. A novel reassortant influenza A(H5N1) virus has been detected across the Greater Mekong Subregion (GMS), causing infections in both humans and poultry since mid- 2022. This virus has recently caused human outbreaks in Cambodia early this year. This virus contains the surface proteins from clade 2.3.2.1c that has circulated locally, but internal genes from a more recent clade 2.3.4.4b virus. The introduction and widespread circulation of this reassortant influenza A(H5N1) virus into the GMS poses a significant risk to both animal and human health, given the historical impact of HPAI outbreaks in the region. Further, this reassortment event indicates not only the adaptive capacity of the virus but also the ever-present risk of the emergence of new, potentially more virulent strains.

In Vietnam, HPAI A(H5N1) viruses persist among poultry, albeit with sporadic outbreaks. Active surveillance across the country indicates circulation of HPAI A(H5) virus in recent years. Poultry vaccination against HPAI A(H5) viruses has been a crucial strategy in Vietnam´s HPAI control efforts. Phylogenetic examination of HPAI A(H5N1) viruses sampled from live poultry markets and outbreaks between January 2022 and December 2023 revealed continued circulation of both clades 2.3.2.1c and 2.3.4.4b in Vietnam. Clade 2.3.2.1c predominantly circulated in southern Vietnam, while clade 2.3.4.4b was found nationwide. A small number of HPAI A(H5N1) viruses detected in live poultry markets in the southern provinces collected in 2023 exhibited reassortment between clade 2.3.2.1c and 2.3.4.4b genes, however no PB2-E627K substitution was detected.

Among diseases transmitted between animals and humans, Avian influenza is one of the five priority infectious diseases according to Joint Circular No. 16/TTLT-BYT-BNNPTNT-2013. Since 2003, 129 human infections with HPAI A (H5N1), including 65 deaths, have been reported in Viet Nam. The most recent avian influenza A (H5) human case had been reported in October 2022 from the northern province of Phu Tho and another avian influenza A(H5N1) death case was notified in March 2024 in Khanh Hoa province in the middle of Viet Nam.

Dr Nguyen Van Long, Director General of DAH, shared government of Viet Nam actions “The Ministry of Agriculture and Rural Development has proposed that the People´s Committees of provinces and cities seriously implement full epidemic prevention measures according to the direction of the Prime Minister, and the Ministry of Agriculture and Rural Development. Strengthen control of smuggling poultry and poultry products. At the same time, direct local authorities to mobilize resources and participation of departments, branches, unions, and socio-political organizations to allocate funds and human resources for the implementation of epidemic prevention and control activities to protect people health, protect livestock herds, ensure a safe poultry food supply, and ensuring social security while promoting the export of poultry and poultry products.”

“FAO is monitoring the situation through the Joint FAO-WOAH network of scientific expertise on animal influenza (OFFLU), and in collaboration with other partners. With financial support from USAID and other resource partners, FAO will continue to provide technical support for the preparedness, prevention and response to influenza A(H5N1) in Viet Nam” stated Dr Rémi Nono Womdim, FAO Representative in Viet Nam

DAH and FAO Viet Nam recommend the following behaviors:

For poultry farmers

? Strengthen biosecurity measures on your farms to minimize risk of introduction;
? Follow correct vaccine schedules and ensure good nutrition for your flock health;
? Report unusual poultry death to your village heads or local animal health authority and
? Do not allow visitors on your farms.

For poultry traders and market vendors

? Only collect poultry from traceable source and sell in permitted place in markets;
? Do not sell poultry outside markets;
? Always wash your hands with clean water and soap after contacting with poultry;
? Use shoes provided by poultry farms when you need to enter production areas;
? Always clean your shoes when you exit markets and

For veterinarians and workers involved in outbreak response teams

? Consistently wear personal protective equipment when exposed to suspected or infected birds to minimize the transmission risk.

For general public

? Regularly wash hands before handling food and often during food preparation, after handling animals;
? Cook food thoroughly, especially meat, poultry, and eggs;
? Wash and sanitize all surfaces and equipment used for food preparation;
? Avoid consume “tiet canh” blood pudding, a Vietnamese specialty prepared with raw blood mainly from ducks;
? Avoid touching sick or dead animals;
? If you have been exposed to likely infected birds, report any symptoms to local health services if respiratory symptoms suspecting zoonotic influenza virus infection; and
? Report any unusual death in birds and poultry to the animal health authority.

Influenza A viruses infect the respiratory and gastrointestinal tracts of birds causing birds to shed the virus in their saliva, mucous, and feces. Influenza A viruses can also infect the respiratory tract of mammals and cause systemic infection in other organ tissues. Illnesses in people from HPAI A(H5N1) virus infections have ranged from mild (e.g., upper respiratory symptoms) to severe illness (e.g., pneumonia, multi-organ failure) resulting in death.

The overall public health risk from currently known influenza viruses at the human-animal interface has not changed, and sustained human-to-human transmission of the viruses from these cases is currently considered unlikely. Although human infections with viruses of animal origin are unusual, they are not unexpected at the human-animal interface wherever these viruses circulate in animals.

Since December 2023, five human cases of infection with A(H5N1) influenza viruses were notified to WHO from Cambodia. The A(H5N1) viruses from the first four cases belong to the H5 haemagglutinin (HA) clade 2.3.2.1c. Viruses belonging to this clade have been detected in poultry since 2014 in Cambodia in longitudinal surveillance done in the animal health sector.