New Strain of Norovirus Sweeping the U.S., after Influenza

Piggybacking off this year’s influenza epidemic, a new strain of the highly contagious norovirus has reached the U.S. from Australia. Just when it seemed like this year’s flu epidemic was finally under control, along comes the CDC with a new plague that’s sweeping the nation: the norovirus.

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 U.S. Centers for Disease Control and Prevention (CDC) stated in the Morbidity and Mortality Weekly Report that the new norovirus strain (called GII.4 Sydney) is currently the leading cause of norovirus outbreaks in the U.S. and recorded 58% of cases of the infection in December.

Norovirus is often confused with the stomach flu because of its coexisting circulation with influenza during winter months.

Norovirus

On an average Norovirus causes

• 21 million cases of illness, involving severe vomiting and diarrhea,
• 70,000 hospitalizations every year in the U.S., and
• 800 deaths.

Where influenza is a respiratory illness, norovirus comes in five forms,

• favors the stomach and intestinal tract,
• causing inflammation of tissues that leads to pain,
• nausea,
• diarrhea and
• vomiting.

According to the CDC, approximately

• 51% of the cases in the U.S. were caused by person-to-person transmission, and
• 20% resulted from contaminated food.

Most infections occur in public places, such as

• schools, nursing homes and
• cruise ships, where the virus can pass easily from host to host.

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.”

Firstly, the new strain of norovirus was identified in March 2012 in Australia and has made people sick on several continents.

Historically, the GII strains have caused more severe illness than other versions of the virus, but officials at the CDC says it is too early in the season to determine if GII.4 Sydney is infecting people at higher rates than in previous years.

The norovirus season runs from November through March and cases typically peak in January.

Dr. John Treanor, chief of the Infectious Diseases Division at the University of Rochester Medical Center, said :

“Although most of the time you recover after 24 or 48 hours, [norovirus] is a reason for people to come to the emergency room, and is even responsible for a small number of death each year. It’s not a completely innocuous virus and can certainly ruin a vacation,”

Norovirus

There are no treatments for norovirus, other than riding out the infection, but Treanor and a group of scientists are currently testing a vaccine developed by LigoCyte Pharmaceuticals. The vaccine shot contains a part of the norovirus’ outer layer, which they hope will generate a strong immune response in those who get immunized.

A vaccine would be critical for preventing the disease from escalating in populations; because it spreads so quickly, norovirus infections are difficult to control.

Dr. Treanor also said:

“You really only have to be exposed to a couple of viral particles to get sick. This makes it very contagious because when you have norovirus, you are dispersing literally millions of particles. When it only takes one or two to make the next person sick, it translates into very high contagiousness.”

Fortunately, the same things you do to protect yourself from flu also helps in holding off infection with norovirus. The CDC recommends the following:

• Wash your hands carefully with soap and water, especially after using the bathroom or changing diapers and before handling food.
• Carefully wash produce and seafood before cooking and consuming them.
• If you are sick, wait 2-3 days after recovering before preparing food for anyone.
• Immediately clean any infected or contaminated surfaces and wash laundry thoroughly.
• rinse fruits and vegetables.

• 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.”

 

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