August 2, 2024

UK health agency raises risk assessment for avian influenza genotype in US dairy cattle

The United Kingdom's Health Security Agency (HSA) on July 26 updated its risk assessment for H5N1 avian influenza B3.13 genotype in US dairy cattle, from three to four on a six-tier scale, noting that it is making the notch up based on moderate confidence.

The group made its initial assessment on the US H5N1 developments in May, when it put the level at three, with a caveat that said it may have risen to four, but with low confidence.

In the update, the HSA said, "There is high uncertainty regarding the trajectory of the outbreak and there is no apparent reduction in transmission in response to the biosecurity measures that have been introduced to date."

Mild zoonotic cases in humans are likely going undetected and unreported, so there isn't enough data to say if the rate is unusually high.

So far, the B3.13 genotype is limited to the United States. It remains hard to gauge whether other genotypes in Europe could trigger similar outbreaks. 

"Levels are indicators that a zoonotic influenza virus outbreak may be an increasing human health threat, either because the opportunities for it to evolve are increasing or because there is evidence that it has already begun to evolve," the group said.

- CIDRAP