A 14th commercial turkey farm in Minnesota has been tainted with the deadly avian flu, following on from four farms that were announced Friday.

The Associated Press reports that the latest farm dealing with the virus is in Kandiyohi county, with 38,000 birds in the affected flock.

The U.S. Department of Agriculture confirmed Friday confirmed that turkeys at four farms in Cottonwood, Lyon, Stearns and Watonwan counties – totaling 189,000 birds between them – had been infected with bird flu.

The USDA says turkeys from these flocks will not enter the food system, and note that the risk to humans is low. No infections in people have been detected.

Since the first bird flu infection was confirmed in Minnesota just one month ago (prompting 40 countries to ban poultry imports), more and more cases have quickly sprung up. The number of affected farms has jumped from four just a week ago, to now 14 in all.

It's popped up in 10 states since the start of the year.

So what's causing it, and what will the impact be?

What's the cause?

While trying to pinpoint what caused the virus to infiltrate the commercial turkey farms' barns, experts are looking up.

Ducks and other migratory waterfowl can carry the virus without showing any symptoms, the World Health Organization says.

Beth Thompson, an official with Minnesota's Board of Animal Health, told Bloomberg they believe that's how the virus is getting around.

The New York Times says the virus likely came in from Canada initially, with the waterfowl flying south. Avian flu was recorded in British Columbia in December.

What's the impact?

The total number of birds killed in Minnesota (the nation's leading turkey producer) is high – about 683,000 before Friday's news, the AP reported, with about one-third dying due to the virus and the rest being euthanized.

But the New York Times says, even with the large swath of infected flocks in Minnesota, the impact on the country's total turkey production has been small – a few hundred thousand out of the 240 million-plus produced each year.

Thompson told Bloomberg she expects warm, dry weather to slow the virus' spread; it generally does better in cooler, wet weather and dies out faster if it gets hot.

Some experts however believe it won't ever really go away.

MPR spoke with David Halvorson, a former University of Minnesota veterinary medicine professor who is now retired. He told MPR that containing the virus – if it's being spread by flying water fowl like is believed – will be nearly impossible.

The only solution then, MPR says, is to figure out how to stop it from getting into commercial barns.