Far more US farm workers are infected with bird flu than officially reported, with some suffering “very severe” symptoms, according to the country’s largest farming union.

H5N1 is currently spreading rapidly across US cattle farms in dozens of US states.

Officially, just three people have been diagnosed with the virus in the past month, all following close contact with infected cows.

In total, 73 people in the US have been officially been recorded as infected with H5N1 since 2024, mostly dairy farm workers. Three have died.

But United Farm Unions (UFU), which represents thousands of workers across the US, said it was aware of many more farmers experiencing symptoms consistent with H5N1 who had not been tested.

“We have now connected with a number of workers and have confirmed that more workers are sick with avian flu symptoms who have not been tested,” the UFU wrote on X.

Symptoms range from “very mild to very severe”, the post added, including mild upper respiratory infections and conjunctivitis to…