A variant of avian influenza circulating widely among birds — and which has caused severe symptoms in some humans — has been detected in US dairy cattle for the first time, authorities have confirmed.
The detection has further raised worries that a worldwide outbreak of H5N1 bird flu, which has significantly impacted the poultry industry, could evolve into a human pandemic.
The US Department of Agriculture (USDA) confirmed Wednesday that bird flu detected in cattle in the southwestern state of Nevada was of the D1.1 genotype.
A different virus genotype — B3.13 — had already been circulating widely among US cattle farms since last year, with more than 950 cases recorded across 16 states
Several people working on the farms were infected with the B3.13 strain last year, but only had mild symptoms.
The D1.1 strain on the other hand has been linked to a small number of serious human cases, including the first US fatality due to bird flu in early January.
Health authorities at the time said the patient, aged 65, had underlying medical conditions and that general risks to the public remained low.
The USDA said on its website that the D1.1 genotype “represents the predominant genotype in the North American flyways this past fall and winter and has been identified in wild birds, mammals, and spillovers into domestic poultry.”
Among cattle, both virus strains produced similar symptoms, according to a Nevada official interviewed by CBS News, including “fever, reduced feed consumption, reduced milk production and mild respiratory signs.”
The growing number of mammal infections has sparked alarm among scientists who worry the virus’s high circulation could allow it to mutate into more dangerous variants.
Those fears have been compounded by President Donald Trump’s efforts to rapidly cut federal spending, with experts warning staff and program reductions could impact public health monitoring.
The bird flu impacts on poultry farms have led to mass culling of flocks and a nationwide shortage of eggs.
