While the United States continues to deal with a significant outbreak of the H5N1 bird flu, officials have now reported the country’s first outbreak of H7N9 – another often deadly strain – in commercial poultry since 2017.
The first signs of the outbreak came on March 8, when chickens at a commercial broiler breeder facility in Noxubee County, Mississippi, began dying in significant numbers. Such sudden death in high numbers is a typical indicator of highly pathogenic avian influenza (HPAI), better known as bird flu, and testing later revealed this to be the case.
It would be understandable to assume that the responsible bird flu strain was H5N1, given the way that it’s devastated poultry farms across the US – but on March 17, the Mississippi Board of Animal Health (MBAH) confirmed that the flock had in fact been infected with another strain of HPAI, known as H7N9.
“This H7N9 virus is a fully North American (AM) virus of wild bird-origin and is unrelated to the Eurasian H5N1 clade 2.3.4.4b virus currently circulating in the United States,” the MBAH said in a statement.
The board also confirmed that no infected birds had entered the food system and that the entire flock – consisting of over 47,000 birds, according to a report from the World Organisation for Animal Health – had since been culled. While no further incidences of H7N9 have been reported, officials are continuing to increase monitoring throughout Mississippi.
This is the first outbreak of highly pathogenic H7N9 in commercial poultry in the US since 2017, when two farms in Tennessee were found to have poultry infected with the strain.
Like H5N1, H7N9 can infect both birds and humans and can cause serious illness and death. According to the World Health Organization (WHO), as of January 31, 2024, there have been 1,658 confirmed human cases of H7N9 infection since 2013, 616 of them fatal.
However, the risk of exposure for the general public is thought to be low, with most cases of H7N9 infection appearing after recent exposure to live poultry. Human-to-human transmission is also thought to be rare.
The reappearance of another bird flu strain comes amid a somewhat tumultuous time for the US’s response to H5N1. Whilst the US Secretary of Agriculture recently announced a $1 billion plan to curb HPAI – and bring down egg prices – the move from the Biden to Trump administration has seen disruption, including the firing and attempted rehiring of some people working on the bird flu response.
