ATLANTA — A new Morbidity and Mortality Weekly Report from the Centers for Disease Control and Prevention (CDC) indicates that several workers who did not recall experiencing symptoms related to highly pathogenic avian influenza (HPAI) were in fact recently infected.

The report, released on Nov. 7, shows that 7% of 115 dairy workers exposed to HPAI through infected cattle in Michigan and Colorado had evidence of contracting the disease, including four who did not recall feeling sick.

CDC noted that all those who tested positive for H5N1 antibodies reported milking cows or cleaning the milking parlor, which the agency sees as higher risk activities. Also of importance, none wore respiratory protection, and less than half wore eye protection.

Following the findings, CDC issued tailored recommendations to further protect workers at the highest risk and contain the spread of the virus.

The agency is recommending extended H5 bird flu testing for all workers following farm outbreaks. Additionally, CDC said to provide the antiviral medication Tamiflu to all workers exposed to the outbreak as a preventative measure — even to workers who don’t show symptoms. Previously, the agency restricted its recommendations only to workers reporting symptoms.

Despite the added efforts for disease mitigation, CDC maintains its stance that the risk to the general public is low and no person-to-person transmission of the disease is suspected.

“There is nothing that we have seen in the new serology data that gives rise to a concern about person-to-person transmission,” declared Nirav Shah, CDC principal deputy director.

“Although we have not seen changes to the virus that would suggest the capacity for it to spread from person to person, we want to keep that risk as low as where it is right now,” he added. “One of the best ways to do that is to identify individuals who have been exposed through greater testing and provide them with Tamiflu to drive down the levels of virus in their body, which again helps us keep that low risk as low as possible.”

Currently, CDC has confirmed 46 cases of HPAI in humans. However, the new study suggests that even more workers have been infected than the reported number.