Some financial commentators are worried that inflation is headed higher, especially after U.S. producer and consumer price increases accelerated in April.

Consumer prices rose 0.3 percent during the month, the most since last June.

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But deflation is the real worry, says CNBC contributor Ron Insana. Sure, prices are increasing for food and energy, he writes on CNBC.com.

But that has "nothing to do with monetary policy," Insana says. "Indeed, if the Fed were to raise interest rates to quell this type of inflation, consumers would fare even worse as the cost of money would join the rising cost of supply-disrupted goods."

The yield curve is flattening around the world, he writes. And, "as history has frequently shown, flattening yield curves imply weakening economic growth and/or falling inflation."

And what about the stock market? "Stocks are getting nervous that the relentless drop in current global interest rates, interest rate forwards, and yield curves everywhere, are reigniting fears of deflation, not inflation," Insana says.

The European Central Bank looks ready to respond to this situation with more easing next month. And more central banks, including the Fed, may have to do the same, he writes.

Some analysts view the rise in U.S. April prices as a positive signal for the economy.

"Growth momentum in the second quarter looks reasonably solid," Michael Feroli, chief U.S. economist at JPMorgan Chase, told Bloomberg News. "There is a little more inflation there than people are giving credit for."

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