#18,376
In March of 2017 (see graphic above) we followed a handful of outbreaks of a genetically distinct North American (NA) lineage avian H7N9 virus (both LPAI & HPAI) across four southern states; Tennessee, Alabama, Georgia, and Kentucky (see here, here, and here).
Despite sharing the same HA/NA designation as their more famous (and far more dangerous) Chinese counterpart - these North American viruses are considered to currently pose a relatively low threat to human health.
LPAI (Low path) H7 or H5 viruses - which are ubiquitous in wild birds - can sometimes make their way into a poultry flock, where they spread, evolve, and occasionally spontaneously mutate into highly pathogenic (HPAI) viruses.
Last week the Mississippi Board of Animal Health reported an outbreak of HPAI in a commercial chicken flock from Noxubee County, which borders Alabama.
Remarkably, this report never specifies the subtype.
A report was also published by WOAH which indicated the affected flock to be 47654 birds and identifies the subtype as HPAI H7N9.
PRESS RELEASE
FOR IMMEDIATE RELEASE: March 12, 2025
Contact: Beth Adcock, Mississippi Board of Animal Health
769-798-3137
beth@mdac.ms.gov / msstatevet@mdac.ms.gov
Highly Pathogenic Avian Influenza Diagnosed in Mississippi Poultry Flock
JACKSON, Miss. – The Mississippi Board of Animal Health (MBAH) has been notified by the U.S. Department of Agriculture’s National Veterinary Services Laboratory that poultry from a commercial broiler breeder chicken flock in Noxubee County, Mississippi has tested positive for highly pathogenic avian influenza. Samples from the flock were tested at the Mississippi Veterinary Research & Diagnostic Laboratory, part of the National Animal Health Laboratory Network, and confirmed at the APHIS National Veterinary Services Laboratories in Ames, Iowa.
Avian influenza does not present a food safety risk; poultry and eggs are safe to eat when handled and cooked properly. According to the U.S. Centers for Disease Control and Prevention (CDC), the public health risk associated with avian influenza in birds remains low. As a reminder, the proper handling and cooking of all poultry and eggs to an internal temperature of 165 ˚F is recommended as a general food safety precaution.
SITUATION: The State Veterinarian has quarantined the affected premises, and birds on the property have been depopulated to prevent the spread of the disease. Birds from the flock have not entered the food system. The MBAH is working closely with federal animal health officials in Mississippi on a joint incident response.The MBAH is actively working with the poultry industry to increase monitoring of flocks statewide. This finding is the third case of highly pathogenic avian influenza (HPAI) in commercial poultry in Mississippi since the spring of 2023. Since November 2024, HPAI has been detected in migratory waterfowl in multiple areas of Mississippi. The poultry industry was notified and put on high alert to increase biosecurity and surveillance for HPAI.
REPORTING: Hobby poultry owners are encouraged to practice good biosecurity and be aware of the signs of avian influenza and report illness and/or death in birds in the MBAH Online Reporting Form https://agnet.mdac.ms.gov/MBAHReportablePublic/birddeathlanding.
Information will be routed to a state or federal veterinarian in Mississippi for assessment. Dead birds should be double‐bagged and refrigerated for possible testing. 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.
Avian influenza in birds can cause sudden death; lack of energy or appetite; decreased egg production; soft-shelled or misshapen eggs; swelling or purple discoloration of head, eyelids, comb, hocks; nasal discharge; coughing; sneezing; incoordination; and diarrhea. A resource for backyard bird health information is online at: https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-diseaseinformation/avian/defend-the-flock-program/dtf-resources/dtf-resources.
Biosecurity information and resources can be found by visiting: https://www.mbah.ms.gov/biosecurity/.UPDATES and INFORMATION: Updates about ongoing avian influenza activities in Mississippi, along with critical disease‐related information, will be posted online at: https://www.hpai.ms.gov/.
As we've seen previously in the United States - and have recently seen in Australia - HPAI H7 outbreaks in poultry can be difficult to contain.
While H7 viruses are generally thought of as being less of a threat than H5 viruses - and primarily an agricultural concern - we've seen some notable exceptions.
- In 2003, the Netherlands saw an outbreak of H7N7 that resulted in the loss of 30 million birds across 1,000 farms, and saw scores of mild human infections and the death of a veterinarian (see Eurosurveillance Human-to-human transmission of avian influenza A/H7N7, The Netherlands, 2003).
- Another analysis, performed by the RIVM (Ministry of Health) found the spread of the virus to be much greater than originally reported, citing as many as 1,000 human infections (see Executive summary Avian Flu Epidemic 2003: Public health consequences),
- Smaller H7 outbreaks, including the 2004 H7N3 outbreak in British Columbia, a small number of human infections in Wales in 2007, and 3 mild cases in Italy in 2013 (see ECDC : Human Infection By Avian H7N7 In Italy) were also reported.
- But the 5-year epidemic of H7N9 in China (2013-2018) - which hospitalized more than 1,500 people, killing roughly 40% of them - demonstrate just how formidable an H7 virus can be.
For now, the HPAI H7N9 virus reported in Mississippi show no signs of posing any kind of serious public health threat.
But, as with all influenza viruses with zoonotic potential, that status quo can always change.
