By Grace WadeThere may be more bird flu cases in humans in the US than we previously thought. Health departments in two states took blood tests of workers on dairy farms known to have hosted infected cattle and found that about 7 per cent of them have antibodies for the disease.

The new guidance comes after blood tests for 115 farmworkers in Michigan and Colorado ... said that efforts to monitor dairy workers for illness have been hindered by several barriers including the reluctance of farm owners and farmworkers to allow testing.

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,