The 2012-2013 flu season is off to an early start, and U.S. health officials warn that it could be a bad one.
The predominant strain so far is called influenza A N3H2. Although not new, it is particularly virulent, which is why this flu season might be severe, according to the U.S. Centers for Disease Control and Prevention.
"This is the earliest regular flu season we've had in nearly a decade, since the 2003-2004 flu season," CDC Director Dr. Thomas Frieden said during a press conference Monday. "That was an early and severe flu year. While flu is always unpredictable, the early nature of the cases plus the strain we are seeing suggests it could be a bad flu year."
"It's time to get vaccinated," he added.
In some areas of the country, flu-like symptoms account for 2.2 percent of doctor visits. At that level, the CDC considers the flu season under way, Frieden said.
Five states are hardest hit right now: Alabama, Louisiana, Mississippi, Tennessee and Texas. Georgia and Missouri are also seeing moderately high levels of flu, Frieden said.
The flu season usually runs from fall through spring, peaking in February.
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