The outbreak resulted in the depopulation of 47,654 birds
Photo: Dima Aslanian/Adobe Stock
A highly pathogenic avian influenza (HPAI) outbreak has recently been reported in a broiler farm in Mississippi. The outbreak involves the H7N9 strain of the virus, a subtype that had not been detected in poultry in the United States since 2017.1
The virus was found in a commercial poultry flock in Noxubee County, located in the eastern part of the state along the Alabama border.1,2 Clinical signs of the H7N9 outbreak, including an increase in deaths, were noticed on March 8, 2025. By March 13, 47,654 birds at the affected facility had been depopulated.
Birds infected with HPAI may exhibit the following signs2:
According to the Mississippi Board of Animal Health (MBAH), the Mississippi Veterinary Research and Diagnostic Laboratory, part of the National Animal Health Laboratory Network, conducted tests on samples from the poultry. The samples were later confirmed positive for HPAI by the Animal and Plant Health Inspection Service (APHIS) National Veterinary Services Laboratories in Ames, Iowa.2
As per the MBAH, the birds on the property were depopulated and did not enter the food supply. Moreover, the affected premises were quarantined by the state veterinarian. Currently, the MBAH and Mississippi’s federal animal health officials are working on a joint incident response.2
“The MBAH is actively working with the poultry industry to increase monitoring of flocks statewide,” wrote the MBAH in its announcement.2 This most recent outbreak of HPAI in commercial poultry is Mississippi’s third case of the virus in these animals since the spring of 2023.2
Since November 2024, HPAI has been identified in migratory waterfowl across various regions of Mississippi, according to the agency. “The poultry industry was notified and put on high alert to increase biosecurity and surveillance for HPAI,” they continued.2
In its announcement, the MBAH emphasized the importance of hobby poultry owners being aware of the signs of HPAI. The agency also encouraged these persons to follow good biosecurity. Illness and/or deaths in birds should be reported through the MBAH Reporting Form, where information will be sent to a state or federal veterinarian in the state for evaluation.
“Dead birds should be double-bagged and refrigerated for possible testing,” wrote the MBAH.2 “Precautions should be taken when handling sick or dead birds including proper handwashing, using gloves, wearing masks, and sanitation of surfaces that come into contact with sick or dead birds to prevent the spread of avian influenza to people.”
According to the World Organization for Animal Health (WOAH), the H7N9 subtype of HPAI comes from a North American wild bird lineage.1 Prior to the most recent outbreak, the last instance of highly pathogenic H7N9 in US poultry was confirmed in March 2017 with outbreaks in 2 commercial poultry farms in Tennessee.
Although the H5N1 strain is the most prevalent strain of HPAI, H7N9 has shown to have a higher mortality rate. The H7N9 strain, according to the World Health Organization, has resulted in the death of 39% of reported humans infections since early 2013.3
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