Federal health officials have called for expanded bird flu testing among farmworkers following a study revealing signs of infection in asymptomatic dairy workers.

Dr. Nirav Shah, principal deputy director of the U.S. Centers for Disease Control and Prevention (CDC), told reporters on Nov. 7 that farmworkers who come into close contact with infected animals should be tested and offered treatment even if they are asymptomatic.

"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 said.

"Some of the persons who did not report being ill might have experienced only very mild symptoms," the study reads. "This finding highlights the need to actively monitor exposed workers by assessing the presence of any mild symptoms and provide a safe environment that encourages reporting of even mild illness and allows for rapid treatment with antivirals to prevent progression to severe disease, without risk for repercussions in terms of job security and pay."

Some workers with HPAI A(H5) antibodies reported illness before infected herds were identified, the study noted. This highlighted the importance of early outreach to dairy workers and swift herd identification through expanded testing and bulk milk monitoring programs.