A new norovirus strain, known as GII.4 Sydney, has been identified as the main cause of norovirus outbreaks in the U.S. from September to December 2012.

The finding came from the Morbidity and Mortality Weekly Report released this week by the CDC (Centers for Disease Control and Prevention).

The new strain was first detected in Australia in march of last year, resulting in several outbreaks in that county, as well as many other nations.

A team of CDC experts gathered and examined data through CaliciNet on norovirus strains linked to outbreaks in 2012 in the U.S. Results showed that the GII.4 Sydney strain was the cause of 266 norovirus outbreaks reported from September to December in 2012.

Dr. Aron Hall, epidemiologist, CDC’s Division of Viral Diseases (DVD), said:

“The new strain spread rapidly across the United States from September to December 2012. The proportion of reported outbreaks caused by this strain increased dramatically from 19 percent in September to 58 percent in December.”

Norovirus is highly infectious. Researchers created a vomiting robot earlier this month to find out how far the very contagious norovirus germs travel.

The leading cause of acute gastroenteritis, which results in vomiting and diarrhea, is norovirus. Over 21 million Americans are affected by the norovirus every year and end up with acute gastroenteritis.

An estimated 800 people die from the virus annually – young kids and seniors are at increased risk for serious illness.

Infected patients typically spread it to others through direct contact. However, it can also spread through water, food, or surfaces that have been contaminated.

This time of the year (winter), people frequently become infected with norovirus. November to April are the most common months, but activity tends to increase in January.

“New norovirus strains often lead to more outbreaks but not always,” revealed Dr. Jan Vinjé, director of CaliciNet. Over the past decade, new strains of GII.4 have emerged about every 2 to 3 years. “We found that the new GII.4 Sydney strain replaced the previously predominant GII.4 strain.”

Novel norovirus strains have been able to be detected earlier due to better surveillance in the U.S. and in other countries. Health professionals as well as the public are able to prevent infections and control outbreaks more efficiently when new strains are identified earlier.

Health experts should be on the lookout for a possible rise in norovirus infections this season as a result of GII.4 Sydney. The CDC advises them to follow the customary prevention and control actions for norovirus.

According to CDC specialists, the best ways to prevent norovirus infection include:

  • wash your hands with soap and water
  • rinse fruits and veggies
  • disinfect surfaces
  • don’t prepare food or care for others while sick
  • cook shellfish thoroughly

Dr. Hall concluded:

“Right now, it’s too soon to tell whether the new strain of norovirus will lead to more outbreaks than in previous years. However, CDC continues to work with state partners to watch this closely and see if the strain is associated with more severe illness.”

Written by Sarah Glynn