JACKSON, MISS. — A variant of avian influenza that has not been identified in the United States since 2017 was recently discovered in a commercial broiler breeder flock in Noxubee County, Miss.

On March 17, the Mississippi Board of Animal Health (MBAH) announced that the US Department of Agriculture’s (USDA) National Veterinary Services Laboratory confirmed the positive trace of H7N9 highly pathogenic avian influenza (HPAI).

This new detection comes at a time when the country is transitioning its approach of mitigating HPAI. In February, Agriculture Secretary Brooke Rollins laid out a $1 billion plan to control the spread of HPAI and address the skyrocketing prices of eggs. Part of the plan included exploring pathways to vaccines rather than continuing with mass culling of birds.

The H7N9 virus could throw a new curveball at regulators and veterinarians as they settle into the latest mitigation strategy and vaccination efforts.

The World Organization for Animal Health (WOAH) was notified of the occurrence of a previously eradicated strain. MBAH noted that, while the USDA has documented H7N9 low pathogenicity avian influenza (LPAI) in its wild bird surveillance this year and previous years, the occurrence in the Mississippi flock was the first high pathogenicity H7N9 subtype in seven years.

The H7N9 subtype is a fully North American virus of wild bird-origin and is unrelated to the H5N1 virus currently circulating in the United States, explained MBAH.

Symptoms of the affected Mississippi flock were recorded on March 8, which namely included a high mortality rate. Totaling 47,700 birds, the flock was depopulated to prevent the spread of the disease. None of the birds entered the food system.

State veterinarians have quarantined the area. MBAH is actively working with federal partners and the poultry industry to increase monitoring of flocks statewide.