Federal and state officials are bracing for a possible return of avian influenza in the fall as warm summer temperatures provide a lull in the number of reported cases.

Outbreaks of the virulent H5N2 virus struck flocks across the country, mostly in the Midwest and along the Pacific coast, starting in December last year.

According to the U.S. Department of Agriculture, farmers killed a total of 48 million birds, two thirds of that number in Iowa alone, to contain the spread of the disease.

Officials suspect the disease spread initially from migratory birds.

The USDA has not reported any new cases since June 17. The drop off in outbreaks is likely due to hot weather suppressing the virus and wild birds hunkering down for the summer.

Bird Bans

State and county fairs across the country have shut down poultry competitions to keep the virus from jumping between farms.

State fairs in Minnesota, Iowa, Michigan, New York, Ohio and Nebraska, have banned all poultry shows.

Indiana initially banned all birds from fairgrounds, but recently lifted restrictions on parrots, canaries and other songbirds as well as doves and pigeons.

The overall ban will lift in mid-September, which covers most of Indiana's country fairs except one held in late September. Aaron Fisher, an extension specialist with 4-H Youth Development at Purdue University, said the ban unfortunately came at a time when most competitors had already raised their birds.

"Well, I think it has been frustrating for some 4-H members, but most of my interaction with people – they have totally understood the reason for the ban. They certainly did not want their birds to get the flu, and didn't want their birds to be a reason why it spread."

Winter is Coming

Agriculture officials say cooler temperatures and southbound birds will likely bring fresh outbreaks.

USDA Secretary Tom Vilsack told Congress this week that a bird flu vaccine tested 100 percent effective for chickens in tests, and is now being tried on turkeys.

However, some officials have raised concerns that use of the vaccine could trigger bans on U.S. poultry. Vilsack is due to speak at a conference in Iowa with poultry industry groups, including the Egg Association, National Chicken Council, the National Turkey Federation, the United Egg Producers, and the USA Poultry and Egg Export Council.

No outbreaks have struck the east coast, but states along the so-called Atlantic flyway are still preparing for the worst.

In Georgia, agriculture officials ran drills on how to quickly kill chickens with foam in case of an outbreak. Ducks and geese have been banned at the Delaware State Fair. Meanwhile, Canada has lifted some quarantines on poultry farms, with plans to release all restrictions by the end of the month.

Read More:

• Eastern Poultry Producers Brace For Avian Flu This Fall As Waterfowl Migrate (Penn State)
• USDA Ready In Case Of Fall Avian Flu Outbreak (Farm Futures)
• Update on Avian Influenza Findings (USDA)
• Avian Flu Worries In The Mix At Delaware State Fair (Delaware News Journal)