DES MOINES, Iowa (AP) — Another 15,0000 chickens and 37,000 turkeys will have to be killed after bird flu spread to two more Iowa farms, state agriculture officials announced Sunday.

Since the outbreak began a month ago, millions of fowl have been killed, many of them in Iowa, which is the nation’s leading egg producer. The latest cases were at a commercial turkey flock in Sac County and in a flock of commercial breeding chickens in Humboldt County,

Because the virus is so infectious and deadly for commercial poultry, entire flocks are destroyed and composted on the farms when they are infected.

The Centers for Disease Control and Prevention said the cases in birds do not present an immediate public health concern. No human cases of the avian influenza virus have been detected in the United States.

It remains safe to eat poultry products. Cooking of poultry and eggs to an internal temperature of 165 ˚F kills bacteria and viruses.