The amount of influenza ravaging the U.S. this year rivals levels normally seen when an altogether new virus emerges, decimating a vulnerable population that hasn't had a chance to develop any defenses.
It's an unexpected phenomenon that public health experts are still trying to decode.
The levels of influenza-like illnesses being reported now are as high as the peak of the swine flu epidemic in 2009, and exceed the last severe seasonal flu outbreak in 2003 when a new strain started circulating, said Anne Schuchat, the U.S. Centers for Disease Control and Prevention's acting director. Swine flu, which swept the globe in 2009 and 2010, sickened 60.8 million Americans, hospitalized 274,304 and killed 12,469, according to CDC data.
"This is a difficult season, and we can't predict how much longer the severe season will last," she said. "I wish there was better news, but everything we are looking at is bad news."
The primary type of influenza this year hasn't changed enough from previous seasons to be considered a novel strain, Schuchat said. The agency's virologists are studying it to determine if there are any other explanations for why it's been so hard-hitting.
"We have a lot to learn still about influenza," she said. "It's a wake-up call about how severe influenza can be, and why we can never let down our guard."
