The first confirmed case of Highly Pathogenic Avian Influenza (HPAI) in a US commercial flock since 2020 was detected in a turkey flock in Indiana on Wednesday, according to the United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS).
The flock was tested after about 100 birds died. The farm is under quarantine and birds on the property were euthanized.
The flock was infected with the H5N1 subtype, the same strain detected in mid-January in wild birds in North Carolina when the first cases of HPAI this season were detected in the States.
The first case of H5N1 in North America this season was detected in Newfoundland and Labrador in late December. Since then, the virus has spread to other locations in Canada and the US.
As of Thursday, over 91 wild birds in South and North Carolina, Virginia, Maryland and Florida had been found to be infected with Eurasian H5 HPAI, with a number of cases specified as H5N1.
The US Centers for Disease Control stated on Wednesday that the public health risk from avian influenza remains low, but added that outbreaks in domestic poultry could result in increased exposure in some groups of people, especially poultry workers. A recent update by the World Health Organization stated that the overall pandemic risk associated with the H5 lineage is considered "not significantly changed" compared to previous years.
HPAI can be carried by wild birds without causing symptoms but can cause illness and death in domestic poultry. Human infections can occur after close contact with infected birds but are rare. No human infections with HPAI have ever been detected in the US.
Some 864 human infections and 456 deaths with the H5N1 subtype have been reported in 19 countries since 2003. The latest human infection was a man who owned ducks in the UK; he recovered from the virus.
A large number of bird flu outbreaks have been reported throughout Europe, Africa and Asia in recent weeks and months, mostly due to the H5N1 subtype, which comes from the H5 lineage, according to the World Organization for Animal Health (OIE). The organization warned that a further increase in outbreaks is expected in the coming months.
Over a million birds were found to be infected with the variant in Israel in recent months, although Israel's Agriculture Ministry declared in recent weeks that the outbreak is now under control.
The OIE has urged countries to increase surveillance for HPAI outbreaks, as the virus has been reported in over 40 countries since July.
The H5N1-6 and H5N8 subtypes of HPAI are circulating in bird and poultry populations across the globe, sparking concern at OIE, which called this an “unprecedented genetic variability of subtypes... creating an epidemiologically challenging landscape.”
Last month, OIE Director General Monique Eloit told Reuters that "this time, the situation is more difficult and more risky because we see more variants emerge, which make them harder to follow."
"Eventually, the risk is that [the virus] mutates or that it mixes with a human flu virus that can be transmitted between humans then suddenly it takes on a new dimension," she said.
Germany’s Federal Research Institute for Animal Health, the Friedrich Loeffler Institute, told the German Deutsche Presse-Agentur (DPA) that Europe is experiencing its “strongest avian flu epidemic ever.”
The institute added that “there is no end in sight” as the virus spreads throughout the continent and around the world, with new cases reported on a daily basis.