WASHINGTON, Jan. 25 (Xinhua) -- A new strain of norovirus called GII.4 Sydney was the leading cause of norovirus outbreaks in the United States from September to December 2012, the U.S. Centers for Disease Control and Prevention (CDC) said Friday in its Morbidity and Mortality Weekly Report.
The new strain was detected in Australia in March 2012, and caused outbreaks in that country and several other countries.
CDC researchers analyzed 2012 data collected through CaliciNet on norovirus strains associated with outbreaks in the U.S. They found that of the 266 norovirus outbreaks reported during the last four months of 2012, 141 were caused by the GII.4 Sydney strain.
"The new strain spread rapidly across the United States from September to December 2012," said Aron Hall, epidemiologist, CDC's Division of Viral Diseases. "The proportion of reported outbreaks caused by this strain increased dramatically from 19 percent in September to 58 percent in December."
Norovirus is very contagious. In the U.S., norovirus is the number one cause of acute gastroenteritis, which leads to diarrhea and vomiting. Each year, more than 21 million people in the United States get infected and develop acute gastroenteritis; approximately 800 die. Young children and elderly adults have the highest risk for severe illness.
Norovirus spreads primarily from infected people to others through direct contact. It also spreads through contaminated food, water, and surfaces.