CDC calls for expanded testing for bird flu after blood tests reveal more farmworker infections

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Federal health officials are calling for more testing and treatment of workers on farms with bird flu

Federal health officials on Thursday called for more testing of employees on farms with bird flu after a new study showed that some dairy workers had signs of infection, even when they didn't report feeling sick.

Farmworkers in close contact with infected animals should be tested and offered treatment even if they show no symptoms, said Dr. Nirav Shah, principal director of the U.S. Centers for Disease Control and Prevention.

The new guidance comes after blood tests for 115 farmworkers in Michigan and Colorado showed that eight workers — or 7% — had antibodies that indicated previous infection with the virus known as Type A H5N1 influenza.

“The purpose of these actions is to keep workers safe, to limit the transmission of H5 to humans and to reduce the possibility of the virus changing,” Shah told reporters.

The CDC study provides the largest window to date into how the bird virus first detected in March in dairy cows may be spreading to people. It suggests that the virus has infected more humans than the 46 farmworkers identified in the U.S. as of Thursday. Nearly all were in contact with infected dairy cows or infected poultry.

Outside experts said it’s notable that the study prompted the CDC to take new action. Previous recommendations called for testing and treating workers only when they had symptoms.

“This is a significant move towards the assessment that these H5N1 viruses are a greater risk than the CDC estimated before,” said Dr. Gregory Gray, an infectious disease researcher at the University of Texas Medical Branch in Galveston.

Every additional infection in animals or humans gives the virus the chance to