In the U.S., state authorities are integral to managing an emerging outbreak of avian influenza that has impacted dairy cattle and, sporadically, humans. These jurisdictions primarily execute virological testing for both bovine and human populations, adopting diverse methodologies. There is growing concern among epidemiologists regarding the sufficiency of current surveillance measures.
The federal health agencies have cautioned that increased viral transmission among cattle may elevate the risk of human cases; however, the immediate public health risk is considered low.
As per the U.S. Department of Agriculture, avian influenza has affected 139 dairy herds in 12 states as of March, with 4 associated human infections reported—the latest in Colorado on July 3.
Human Testing: By early July, health departments in 5 states reported conducting avian influenza tests on 99 individuals: Michigan (56), Texas (20), Idaho (8), Colorado (8), and New Mexico (7). Conversely, North Carolina, Ohio, South Dakota, and Minnesota reported no testing since the dairy-related outbreak onset.
States have implemented varied testing protocols, generally influenced by direct exposure to infected livestock or symptomatology. Responses from Wyoming and Kansas regarding their testing statistics were not obtained, and Iowa's health department is monitoring symptom development in all exposed individuals, though specific testing figures were not provided.
The Centers for Disease Control and Prevention reported that it has tested at least 53 individuals exposed specifically to infected dairy cattle. This discrepancy arises because state-level testing may include exposures to other infected species, explained CDC spokesperson Jason McDonald.
The CDC recommends that clinicians liaise with local and state health departments for testing indications and promptly report any positive or inconclusive results to the CDC.
Cattle Testing: States with confirmed cases in dairy herds undergo testing based on farmer requests, for research, or other specific reasons, according to representatives from the agriculture departments.
Iowa has instituted a protocol requiring testing of all dairy herds within a 20-kilometer radius of any avian-influenza-affected poultry farms, currently encompassing approximately 25 to 35 herds, said Don McDowell of the Iowa Department of Agriculture and Land Stewardship.
Minnesota’s approach has been to test farms that had contact with affected herds, focusing on tracing potential transmission vectors such as suppliers, equipment, and personnel, stated Brian Hoefs of the Minnesota Board of Animal Health.
Following a USDA mandate in May, testing is required for all lactating dairy cows before interstate commerce, representing the sole national directive thus far, with about 6,600 cows tested under this requirement.
The USDA continues to support state efforts in controlling and potentially eradicating avian influenza, which may involve expanded testing protocols, said a USDA spokesperson.