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This past December, the first case of avian flu was reported in Oregon. The second, in Washington state, was documented in early January. The third was ­detected six days later. And the fourth, fifth, sixth and seventh all surfaced before month’s end.

At the time, there was little sense of how serious the problem would be. Avian flu, though it had proved lethal elsewhere in the world, was unfamiliar to farmers in the United States. And February, which brought only three additional cases, eased anxiety a bit.

But today, farmers from Iowa to California have learned that there is nothing forgiving about H5N2 — this particular strain of bird flu — which has spread like wildfire, paralyzing chicken farmers throughout the Midwest and casting a gloomy shadow over the U.S. egg industry.

“I can’t tell you how many farmers this is affecting,” said Oscar Garrison, director of food safety for United Egg Producers, which represents farmers responsible for almost every egg-laying hen in the country. “It’s been absolutely devastating. Just abysmal.”

The numbers are, indeed, hard to fathom. As of this week, the flu has affected almost 40 million turkeys and chickens, well over 80 percent of which are egg-laying hens, according to the Department of Agriculture. Some 25 million birds in Iowa alone are believed to have been exposed. In all, more than 10 percent of the entire U.S. egg supply is likely to have been affected by the outbreak.

"It's hard to find a farmer that isn't deeply concerned at the moment," said Garrison.

But the consequences extend well beyond the immediate ones felt by egg farmers, who have been forced to slaughter their hens by the millions. Fewer egg-laying hens means fewer eggs, fewer eggs means the potential for a shortage in supply, and a shortage in supply means the eggs that are available will be available only for an added cost.

Price spikes have, in fact, already happened. The wholesale price of eggs sold in liquid form (a.k.a egg beaters, the kind used by large food manufacturers) has more than doubled — from $0.63 per dozen to more than $1.50 since late April. Although it has yet to force all major food companies to charge more for their egg-laden foods, many, including McDonald's and General Mills, are already feeling the heat.

The reality is that any company that sells anything made with eggs (bread, pasta, dessert) will probably be affected — if not already, then soon.

The price of eggs sold in their shells at the supermarket has yet to budge because the vast majority of eggs removed from production were for egg beaters sold to companies. But it’s probably only a matter of time before the ­grocery-store dozens are also are affected by the outbreak.

“Look, there is pretty much no doubt that this will have an effect on the supply of all eggs,” Garrison said. “That will come with its price consequences.”

What sort of price consequences? That part is unclear.

A report this month by the Egg Industry Center, which closely follows the egg market, explained that the scale is simply too large for its price model to predict.

"A large fluctuation such as the loss of millions of laying hens was never considered in the design of the model that is currently in use," the report says.

The most troubling aspect of the recent outbreak, however, might be how fruitless efforts to contain the flu have been. The USDA suspects that the virus entered the country by way of a migratory bird, but it’s unclear how it has since spread. Some, including Agriculture Secretary Tom Vilsack, think it could just as easily be spreading because of human error.

"We've had circumstances recently where folks have been using pond water, for example, to feed and to water their birds," Vilsack told NPR on Thursday. Well, that's a problem because the pond water could be contaminated."

Part of the failure to pinpoint what has allowed the virus to proliferate is that there is only a moderate understanding of how the virus works. (Scientists say they are confident, however, that the flu doesn’t jump to humans.)

“How can you figure out how it’s spreading from farm to farm, and state to state, when you don’t even know the mechanism by which it’s spreading?” said Garrison. “How can you build a fence when you don’t know how big it needs to be, or what it needs to be made of?”

There is hope that as temperatures rise this summer, the virus will weaken, and eventually die out. If it doesn’t, the damage will continue to mount, for egg farmers and egg lovers alike.