The fourth detection was in Sac County in northwestern Iowa on Feb. 19, where 29,665 turkeys were destroyed and the second in O'Brien County, also in northwestern Iowa, where 40 commercial layer birds were destroyed. The first detection of the disease was in eastern Iowa in Clinton County in early January.

Scientists are sounding alarms about a genetic mutation that was recently identified in four dairy cow herds, nearly one year after H5N1 bird flu was first reported in Texas dairy cattle.