Governor Terry Branstad declared a state of emergency for Iowa on Friday, citing risks from the rapidly spreading bird flu outbreak, Reuters reports. The announcement was made after officials identified the virus’ presence at four new poultry farms. Iowa is the third state to declare a state of emergency, after Minnesota and Wisconsin did so in April.

According to Reuters, Iowa is the United States’ top egg producer. Nationally, the outbreak “either has led or will lead” to the extermination of as many as 21 million chickens and turkeys. More than 16 million birds have been infected in Iowa alone, the Wall Street Journal reports.

From Reuters:

The measure expands the efforts of the state’s emergency response plan, and authorizes various state entities access to additional resources, supplies and equipment to track and contain the influenza outbreak. It also allows for the removal and disposal of infected animals on either public or private lands and lifts weight restrictions on trucks hauling culled flocks, among other things. In addition, the action allows the state and local law enforcement to set up checkpoints and road blocks anywhere in the state, including areas outside of quarantined farms.

The declaration is effective immediately and will remain in effect at least through the end of May. The Journal reports that, according to the U.S. Centers for Disease Control and Prevention, no human infections have thus far been identified, and that this strain poses a very low risk to humans.