 But if you're not testing, you don't know where it is, you can't do that kind of work. It's been a couple of weeks since bird flu has been confirmed in cattle or poultry in an Iowa operation. Since March, six farm workers in Texas, Michigan, and Colorado have tested positive for bird flu. Employees at Iowa facilities where the virus has been confirmed among birds or cattle have been tested, but Neg says there have been no human cases of bird flu in Iowa.