Via CIDRAP, Lisa Schnirring brings some much-needed clarification to a big story: North American-origin H7N9 isolated from Tennessee farm. Excerpt and then a comment:
Follow-up testing at the US Department of Agriculture's (USDA's) National Veterinary Services Laboratories on the highly pathogenic H7 virus implicated in an outbreak at a Tennessee poultry farm indicates that the strain is H7N9 but is different from the H7N9 fueling outbreaks in China.
In other US avian flu developments, US agriculture officials yesterday reported a low-pathogenic H5N2 outbreak at a turkey farm in Wisconsin, the same day they announced the highly pathogenic H7 outbreak in Tennessee.
Tennessee H7N9 distinct from China lineage
In a statement, the USDA's Animal and Plant Health Inspection Service (APHIS) said the full genome sequencing reveals that all eight gene segments from the Tennessee H7N9 virus are from the North American wild bird lineage.
"This is NOT the same as the China H7N9 virus that has impacted poultry and infected humans in Asia," APHIS emphasized, adding that though the subtype is the same, the virus is different and genetically distinct from the China H7N9 lineage.
The outbreak at a commercial chicken broiler-breeder farm in Tennessee's Lincoln County, located in the south central part of the state, killed 700 of 72,800 birds.
The USDA said it continues to work with the Tennessee Department of Agriculture on the joint outbreak response and that surviving birds on the affected farm have been culled and burial is in progress. An epidemiologic investigation is under way to identify the outbreak source.
Federal and state authorities are conducting surveillance testing at poultry farms in an expanded 10-mile radius of the affected farm, and poultry movement restrictions have been put in place in a control zone to prevent the virus from spreading. As of yesterday, all commercial farms in the surveillance zone have been tested, and all of the tests were negative.
Commercial and backyard poultry will be monitored for illness, and all flocks in the surveillance are will be tested again.
The last H7 outbreak involving US poultry struck Indiana poultry farms in 2016. H7N8 was identified as the subtype, which hadn't been seen before in the United States. Most of the H7N8 outbreaks were low-pathogenic, but a highly pathogenic version was identified in one of the events, suggesting that the strain became more lethal as it spread.
The original Chinese H7N9 confounded everyone because it didn't make poultry sick; humans were the sentinel species alerting us to its presence in birds. That's recently changed, with some Chinese poultry clearly ill whether local humans are ill or not.