Some 24 million poultry birds like chicken and turkeys have already been lost, either because they died from the virus or were killed to prevent its spread. But unlike a similar bird flu outbreak seven years ago, this one is unlikely to just burn itself out.

That’s because this particular flu virus seems capable of hanging around in populations of wild birds, which can pass the virus on to poultry farms. While chickens and turkeys with the virus quickly sicken and die, some waterfowl can remain healthy with the virus and carry it long distances.

Scientists believe that wild migratory birds brought this virus to North America a few months ago. Since then, more than 40 wild bird species in more than 30 states have tested positive. This strain of bird flu virus has turned up in everything from crows to pelicans to bald eagles.