U.S. Flu Epidemic Fizzling Out

Jan. 29, 2004 -- It was bad, it was scary -- and now the U.S. 2003-2004 flu epidemic is just about over.

"We think it's over," CDC flu chief Nancy Cox, PhD, tells WebMD. "There's no sign of an upswing anywhere in the country. We don't think there will be a second wave."

As of Jan. 24, only one state -- Delaware -- reported widespread flu. Americans aren't seeing their doctors for flu-like illnesses any more than they usually do. And while the death rate from pneumonia and influenza is still above a statistical measure called the "epidemic threshold," it, too, has peaked and is going down.

It's only been a few weeks since flu was widespread in 45 states. Scott Harper, MD, MPH, acting deputy section chief at the flu branch of the CDC's National Center for Infectious Diseases, presented an overview of the flu season at this week's meeting on pandemic influenza, sponsored by the Southeastern Center for Emerging Biologic Threats and Emory University in Atlanta. His U.S. map uses red to designate states with widespread flu.

"The red color across the map of the country looked like something from The Andromeda Strain," Harper said. "It was an early flu season with flu-like illnesses occurring weeks earlier than in the last bad flu season we had."

In a normal year, the CDC usually continues to recommend flu vaccination for high-risk people until the flu season officially ends in spring. This year the question is moot. There's no more vaccine to be had. Once in a great while, late in the flu season, there's a second wave of flu as a different virus gathers steam. But if that were going to happen, Cox says, there would be some sign of it by now.

A Bad Year for Flu

This year, flu hit early. And it hit hard. Why? The main reason is that this year's Fujian flu is a kind of flu known as H3N2. It's a particularly nasty type of flu bug. And the Fujian flu that broke out this year is a new subtype. This year's flu vaccine had a "Panama" H3N2 component -- which seems not to have been very effective.

Just how well did the flu vaccine work? Some experts say not at all, others say it may have prevented severe disease at least some of the time. A first down-and-dirty look at the issue -- in a Denver hospital -- shows that people who got vaccinated were just as likely to get flu-like symptoms as those who didn't get the vaccine. But that study didn't actually test for flu. And it didn't look at whether flu symptoms may have been worse in unvaccinated people. The CDC is studying the issue in more detail.

At least one in four flu cases were due to the older Panama flu. This suggests that people who rolled the dice and didn't get their flu shots lost their bets.