Could it be blowing from farm to farm in the dirt? Could determined starlings and pigeons be carrying it into poultry houses on their feet? Is it spreading in feed, or being carried on truck tires? Federal agriculture officials are looking everywhere they can think of for H5N2 bird flu, which has spread to poultry flocks in 14 states and killed or forced the slaughter of more than 39 million birds.

Highly pathogenic avian influenza has never spread like this before in the United States, and it’s flummoxed the U.S. Department of Agriculture, farmers and scientists alike. “The one question that we cannot answer is how is it getting from the migratory birds into these flocks,” said Dr. Jarra Jagne of Cornell University, who’s studied avian influenza outbreaks around the world. FULL REPORT