Bird flu has been confirmed in a domestic flock of birds in central Iowa.

It’s the 20th site in Iowa where bird flu has been confirmed this year and the first case reported in the state since May. State officials say there were 48 birds in the flock in Dallas County and all have been killed to prevent the spread of the virus.

Iowa Agriculture Secretary Mike Naig said the case isn’t unexpected as the virus has been confirmed this fall in neighboring states as wild birds migrate south. Wild birds can carry the disease, without falling seriously ill. The fall migration of ducks, geese and other water fowl making its way south through Iowa will reach its peak in November.

Iowa is the nation’s number one egg producer and among the 10 producers of turkeys and Iowa has ben hit harder by bird flu than any other state this year. More than 13 million birds in commercial operations and domestic flocks in Iowa have either died from the virus or been killed to prevent its spread.