The WHO has expressed concern over an unexpected H5N1 avian flu outbreak in US dairy cows, with significant viral presence in the milk from at least 16 herds across eight states.

The U.S. Department of Agriculture acknowledges cow-to-cow transmission in dairy herds but the precise transmission method remains unidentified.

A dairy worker in Texas has been infected, indicating potential risks to humans.

Vaccines and therapeutics for H5N1 are in development, with candidate vaccine viruses ready for a possible pandemic.

Initially impacting older cows, recent data indicates that younger cattle are now also contracting the virus.

The WHO advises the public to practice food safety measures, including consuming pasteurized milk, and alerts to the possibility of the virus evolving to infect and transmit between humans.

There are no current quarantines on affected dairies, but the USDA suggests limiting cattle movement, testing, and enhanced safety and cleaning practices to preclude the need for regulatory restrictions.