Last year at this time we told you about a new strain of norovirus, called GII.4 Sydney that the CDC was tracking. Last week, the North Carolina Department of Health and Human Services issued a warning about an outbreak in that state.
The CDC has been studying this new strain. They now have information and statistics on the strain, and have analyzed data from outbreaks in five states.
Since norovirus is the most common cause of gastroenteritis worldwide, and is often transmitted through contaminated food and drink, the discovery of this new strain is important. Norovirus causes 20 million illnesses every year in the U.S., causing 70,000 hospitalizations and 800 deaths. Very few Americans have resistance to this strain. This new emerging strain has caused acute gastroenteritis outbreaks in New Zealand, Japan, Western Europe, and Canada.
A total of 637 norovirus outbreaks were reported in Minnesota, Ohio, Oregon, Tennessee, and Wisconsin from August 1, 2012 to April 16, 2013. Sequence data were available for 358 of those outbreaks. Those outbreaks were more likely to have the transmission mode as foodborne; most occur at restaurants. The proportion of outbreaks attributed to GIII.4 Sydney strain increased from 8% in September 2012 to 82% in March 2013. In December 2012, GII.4 Sydney became the predominant strain.
Public health officials are concerned about an increase in incidence and severity of norovirus outbreaks. This has not happened yet. More outbreaks attributed to the GII.4 Sydney strain occurred in healthcare-related settings. The virus disproportionally affects older persons. Most patients have diarrheal illness and are less likely to have vomiting, fever, and abdominal cramps.
To prevent the spread of norovirus, clean up vomit and diarrhea immediately and sanitize the area with a diluted bleach solution, since most disinfectants are not effective against the virus. Do not prepare or serve food for others while you are sick and for at least 48 hours after you are better. Wash your hands well after using the bathroom and changing diapers and before you prepare and eat food.
