Most commercial chicken and turkey farms that were infected by the bird flu have been cleared to restock, agriculture officials said Friday, but scientists still will keep a close eye on migrating birds and test thousands to see if the virus is present.

No new cases have been reported since June 17 when the last Iowa farm said chickens were dying from the H5N2 virus.

However, wild birds’ southern migration has been delayed by a warmer fall, so officials still need about a month to assure farmers there were no recurrences, Iowa Secretary of Agriculture Bill Northey said. Samples have been tested from more than 19,000 wild birds across the United States so far and plans are to test 38,000 total, U.S. Department of Agriculture veterinarian Dr. Kevin Petersburg said.

The U.S. government has paid out $200 million to farmers for lost birds and nearly $500 million to farmers and contractors who helped euthanize birds and disinfect farms, Petersburg said.

Of the 219 farms nationwide that were affected by the bird flu, all but five of the commercial operations have completed cleaning and disinfecting barns and are being allowed to restock, Petersburg said. Turkey farms should be restocked by mid-December but egg farms will continue introducing new hens next year and into 2017, industry officials said.

Bird flu first surfaced on the West Coast in December and spread to flocks in 15 states over six months, resulting in the death of 48 million birds. Iowa lost the most – nearly 32 million, and mostly egg-laying chickens. Minnesota, the leading turkey producer, lost nearly 9 million birds.

Impact on the availability of Thanksgiving whole turkeys will be minimal, said Gretta Irwin, executive director of the Iowa Turkey Federation. Frozen whole turkeys are selling for around 79 cents to 99 cents a pound and fresh whole birds are around $2 a pound.