Bird flu spreads to mammals, fears of human transmission

Highly pathogenic avian influenza, commonly called bird flu, has increasingly spread to mammals and infected hundreds of people, raising concerns that it may lead to human-to-human transmission and turn into a new pandemic.

Cases of the disease in mammals have mostly been detected in the Americas and Europe.

Sheep were added to the list on Monday with the UK government announcing a first case had been detected at a farm in northern England.

Some of the mammals such as dairy cows and sheep are farmed and so interact closely with humans, increasing the threat of transmission, while others have much less contact with people.

Pigs represent a particular concern for the spread of bird flu because they can become co-infected with bird and human viruses, which could swap genes to form a new, more dangerous virus that can more easily infect humans.

Here are the types of mammals, other than humans, in which the virus — which has also infected hundreds of wild and captive bird species — has been detected between 2016 and 2025, according to data gathered by the European Food Safety Authority and US Department of Agriculture.

Bird flu has been detected in various mammal species across multiple countries between 2016 and 2025. 

The virus has spread widely, affecting both wild and domestic animals, raising concerns about its potential transmission to humans.

In North America, infections have been reported in animals such as alpacas, bobcats, Canadian lynxes, coyotes, fishers, foxes, mountain lions, raccoons, skunks, squirrels, and even domestic cats and dogs. 

The United States has seen a significant number of cases, including in leopards, tigers, and servals. Additionally, domestic pigs in France and Italy have tested positive, while goats in the US have also been affected.

Marine mammals have not been spared either. Various species of seals, sea lions, dolphins, and porpoises have been infected across countries like Canada, Chile, Peru, the United Kingdom, and the United States. 

Alarmingly, cases have also been detected in Antarctica, where crabeater seals and southern elephant seals have tested positive.

In Europe, infections have been found in badgers, beech and pine martens, polecats, otters, and foxes in countries like the Netherlands, Germany, Belgium, and Finland. 

Caracals in Poland and wild dogs in Finland, Japan, and the UK have also been affected. The UK recently confirmed its first case in sheep, adding to growing concerns about farm animals being exposed to the virus.

The wide range of infected mammals highlights the virus’s ability to cross species barriers. 

Pigs are particularly concerning, as they can be co-infected with both bird and human flu viruses, potentially leading to the emergence of a strain that could spread more easily among humans. 

With bird flu continuing to circulate among animals, scientists and health officials are closely monitoring the situation to prevent a possible human outbreak.