Along with avoiding the regular flu this year, Americans might have to take extra precautions to avoid catching a new strain of norovirus, otherwise known as the stomach flu.
This new strain is said to be responsible for the majority of stomach flu outbreaks between September and December, according to the Centers for Disease Control and Prevention.
A little over half of the norovirus outbreaks last fall were caused by the new strain, called GII.4 Sydney.
January is the "peak" in norovirus outbreak season, which usually occurs from November to April. But it is too soon to tell whether the new norovirus will cause more outbreaks.
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The norovirus changes every two to three years, and the current strand was discovered in Australia last March.
Dr. Jan Vinje, director of CaliciNet, the CDC's surveillance system for the flu, said new strands often lead to more outbreaks "but not always."
Norovirus is one of the most contagious, infecting about 21 million people in the U.S. each year, and killing about 800. Younger children and older adults are at a higher risk for severe illness.
About half of all outbreaks caused by the new strain were spread from person to person, 20 percent were from foodborne illness, 1 percent from waterborne illness, and 28 percent were of unknown origins.
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The CDC plans to continually watch the new strain, which will enable it to determine its public health implications.
As with any flu prevention, the best way to prevent the new norovirus strand is by hand washing with soap and water, along with disinfecting surfaces, rinsing fruits and vegetables, cooking shellfish thoroughly, and not preparing food or caring for others while sick.
Experts say the recent outbreaks of the flu and whooping cough are unrelated to the norovirus strain.