Is the world heading towards a bird flu pandemic?

Fears the world is heading towards another pandemic are growing, as new data shows the spread of the deadly bird flu virus has begun to accelerate and move between species.

Bird flu (H5N1) originated in China, in the late 1990s. Seasonal migration then spread the virus globally, leading to outbreaks in domestic and wild birds worldwide. Since then, the virus has spread to livestock.

First infecting cattle in the United States in 2023, genetic data shows the virus is adapting to mammals, jumping not only between cattle but also to other livestock, with the first case of sheep infection confirmed on a UK farm last month.

And fears were further heightened after it was detected in dairy cattle, a host species not commonly associated with the virus, showing its ability to adapt.

Threat to humansAccording to the World Health Organization (WHO), since 2003, there have been 954 confirmed human cases of bird flu, of which around half of the patients have died.

Now there are increasing concerns the virus could infect the human population on a wider scale.

These developments significantly heighten pandemic concerns, with scientists calling for urgent, coordinated public health responses.

“While the current public health risk is low, the CDC is watching the situation carefully and working to monitor people with animal exposures,” said a spokesperson for the Centers for Disease Control and Prevention.

How the virus is spreadingTo understand how the virus is spreading and the threat is poses to humans, a team of researchers from the United States Department of Agriculture studied how the strain evolved and spread from the first detected North American cattle infection.

They analysed genetic data from more than 100 virus samples that had mixed with local, less dangerous bird flu strains. They also included newly sequenced genomes from infected cattle and outbreak reports. The researchers found that once inside the cattle population, the virus spread between cattle quickly.

It also jumped to other species, including poultry, raccoons, domestic cats, and wild birds such as blackbirds and pigeons.

Genetic analysis revealed the virus has developed mutations associated with adaptation to mammals. Alarmingly, some of these mutations are now firmly established in the viral population.

“Our study demonstrates that influenza A virus is a transboundary pathogen that requires coordination across regulatory agencies and between animal and public health organisations to improve the health of hosts and reduce pandemic risk,” says Thao-Quyen Nguye, author on the study.

Source: Emergence and interstate spread of highly pathogenic avian influenza A(H5N1) in dairy cattle in the United States

Published online: 25 April 2025

DOI: 10.1126/science.adq0900

Authors: Thao-Quyen Nguyen, Carl R. Hutter, Alexey Markin et al.