The humble egg, one of nature’s perfect foods, a self-packaged, relatively inexpensive source of protein that can serve as a lowly hangover remedy or help a souffle rise to heavenly heights, is also a great teacher. It’s helping Americans understand how a free-market economy works: When demand is high and supply is low, prices rise.

If you’ve been to the store recently and feel like you’re spending more money on eggs than in the past, you are not alone. A recent outbreak of avian influenza, or bird flu, has disrupted egg production in the United States.

A new bird flu strain was detected on a California duck farm. But what's the difference between H5N9 and H5N1, and is it safe to eat poultry? A doctor explains.