An outbreak of highly pathogenic avian influenza H5N1 in Colorado has spread from dairy cows to a nearby poultry farm.

Five workers involved in culling infected chickens experienced mild illnesses, including conjunctivitis and flu-like symptoms.

The virus in the workers is closely related to the virus in the chickens and dairy herds, doubling the number of human cases linked to the dairy cow spillover.

Officials are investigating a hypothesis linking the dairy and poultry farms but have not confirmed a direct source of infection.

The primary mode of virus spread appears to be through the movement of cows, people, and equipment between farms.

High temperatures during culling made it difficult for workers to use protective gear properly.

The outbreak has affected numerous herds across multiple states, with millions of birds affected.

Investigations by the CDC and USDA are ongoing to prevent further transmission and contain the virus.

Poultry farms in Australia are also facing outbreaks of avian influenza, raising concerns of potential human spread.

Companies like Moderna, GSK, and Pfizer are developing mRNA vaccines adaptable to virus changes, alongside traditional egg-based and cell-based vaccines.

Strategies like universal flu vaccines and bird vaccination are being explored to prevent potential pandemics.

Despite the current low risk of bird flu transmission to humans, efforts are being made to increase vaccine availability for future preparedness.