The devastating avian influenza sweeping the Midwest has forced the mass slaughter of nearly 40 million diseased chicken, turkey and wild birds in order to contain the outbreaks, according to the latest grisly numbers from the U.S. Department of Agriculture (USDA).

According to the USDA, since it was first detected in December 2014, there have been several ongoing highly pathogenic avian influenza cases along the Pacific, Central and Mississippi Flyways (or migratory bird paths). The strains in particular, H5N2 and H5N8, have been found in wild birds, as well as backyard and commercial poultry flocks.

This is the worst epidemic of bird flu in the nation's history. Egg-producers in Iowa, the top egg-producing state, have been hit the hardest, with a shocking 40 percent Iowa's egg-laying hens dead or to be euthanized.

In a report from Harvest Public Media (via NPR), while some local incinerators are burning dead birds 24 hours a day, other landfills have been turning away the carcasses for fear of contamination and neighbors' complaints. Listen here:

"I've been in the landfill business probably 26 years, and I've never ever seen this kind of volume," said Randy Oldenkamp, director of the Northwest Iowa Area Solid Waste Agency, in the report. "And I hope I never do again."

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Prices for eggs in the Midwest have climbed at a rate of 5 percent a day for the past week as supplies dwindle, according to the Associated Press. A dozen large eggs reportedly starts at $1.88, which is 58 percent higher than the prior month. Chicken and turkey sales have also been affected.

Agricultural economist said that bird flu could cost nearly $1 billion to Iowa and Minnesota, the two states hit the hardest. Minnesota, the top turkey state, has lost more than 8 million birds.

The USDA told TIME that some of the viruses currently seen in the U.S. outbreaks originated in Asia and spread via migratory fowl.

Research is still being done to see how the virus has spread so rapidly. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told Harvest Public Media that the poultry industry is in uncharted territory. The virus is "doing things we've never seen it do before," so scientists' understanding is very limited, he said.

"Influenza viruses have thought in the past to be transmitted by birds to birds in close contact and that it was only through that kind of transmission that we need to be concerned," Osterholm added. "Now we surely have a very dynamic situation in the Midwest. It's also a situation where we no longer can assume it's just migratory birds."

The USDA also noted that while "the high number of birds slaughtered during this outbreak is hard for farmers involved, but 30 million is still considered a small percentage of the overall U.S. poultry population." According to the agency, in 2014 the U.S. poultry industry produced 8.54 billion broilers, 99.8 billion eggs and 238 million turkeys.

The Centers for Disease Control and Prevention says the risk of human transmission is low. For you to stay safe, the CDC has told the general public to avoid contact with wild birds and chickens or turkeys that appear sick or have died.

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