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From NPR News, this is ALL THINGS CONSIDERED. I'm Melissa Block.
ROBERT SIEGEL, HOST:
And I'm Robert Siegel. This winter, a nasty infection has been sweeping the land. It's a stomach bug called norovirus. And now the Centers for Disease Control and Prevention says this year's strain is entirely new and has overtaken one that emerged three years ago, which may explain why this seems to be a particularly bad year for intestinal illness, as NPR's Richard Knox reports.
RICHARD KNOX, BYLINE: You can't mistake norovirus. It causes two or three days of severe vomiting and diarrhea, and although a lot of people call it stomach flu, it has nothing to do with influenza. That's a respiratory virus. Norovirus attacks the small intestine.
Every year, it infects 21 million Americans, making it by far the most common intestinal illness. Jan Vinje of the CDC says this year's model is one that's never been seen before.
JAN VINJE: It popped up in Australia, and it was characterized in a laboratory in Sydney in March of 2012. It was exactly the time that we anticipated a new strain to emerge.
KNOX: That's because a new norovirus strain comes around every few years. And right now, the Australian strain is scoring a decisive victory in this survival of the fittest contest.
VINJE: This virus spreads very rapidly and emerges as the winner of the battle. It really is, it's a battle between the most fit strain and most virulent that wins the game here.
KNOX: Vinje says you can get a raging norovirus infection if you're exposed to as few as 17 virus particles.
VINJE: So a few droplets, invisible droplets on a surface or on a doorknob can get you sick.
KNOX: And unlike many, this virus can survive outside the human body for long periods.
VINJE: So on surfaces, it can survive for sometimes for a couple of weeks.
KNOX: Really? So one of the most contagious viruses out there.
KNOX: You can avoid it, but the best way is not by squirting a lot of those sanitizing gels on your hands.
VINJE: We don't recommend to use only hand sanitizers. We think that the physical removal is the most efficient.
KNOX: That means scrubbing vigorously and often with soap and water for longer than you ordinarily do. Twenty seconds is good. That's about how long it takes to hum "Happy Birthday" to yourself twice. And if you get the stomach bug anyway, try to drink as many fluids as you can manage to keep down. The big problem with these infections is dehydration, which can sneak up on you. That's why norovirus puts nearly 70,000 Americans in the hospital every year and kills about 800, most of them people over 65. Richard Knox, NPR News. Transcript provided by NPR, Copyright NPR.