After a new study showed that bird flu has spread to dairy farm workers more often than previously known, the US Centers for Disease Control and Prevention is expanding its recommendations for testing and treatment of workers on farms where animals have tested positive.

CDC officials said the study suggests asymptomatic workers who engage in jobs that put them at high risk for exposure at poultry and dairy farms might be at heightened risk for infection.

The Centers for Disease Control and Prevention (CDC) is updating its recommendations for testing, treatment and protection for workers who may be exposed to animals infected with bird flu. The update comes after the agency found evidence of dairy workers with positive antibodies,