CDC Report Finds Norovirus Outbreak In US Has Taken A Stronghold, Cases Rising
January 25, 2013

CDC Report Finds Norovirus Outbreak In US Has Taken A Stronghold, Cases Rising

[Watch Video: Scientists Create Simulated Vomiting Norovirus System]

Lawrence LeBlond for - Your Universe Online

The US Centers for Disease Control and Prevention (CDC) found that more than 260 cases of the stomach flu seen in the US between September and December 2012 are actually attributed to a new strain of norovirus known as GII.4 Sydney. Health experts do not think it is a particularly dangerous strain, but admit it is different, and might be more difficult for some to fight off than others.

The outbreaks from the new strain have been steadily growing throughout the world and in the US, and experts believe it now accounts for nearly 60 percent of flu cases reported.

The CDC´s Morbidity & Mortality Weekly Report, released on Thursday, shows that the new strain originated last year in Australia and has quickly been taking a stronghold worldwide.

The bug, which causes gut-wrenching pain, nausea, forceful vomiting, and diarrhea, begins very suddenly and lasts for up to three days. Most people recover without treatment, yet some require intravenous fluids to rehydrate the body. It is most dangerous in the elderly and is especially problematic in children. Stomach bugs like norovirus typically strike more than 21 million Americans every year and, according to CDC estimates, about 800 people die from the infections.

Norovirus–originally known as Norwalk virus–is usually spread to others by direct contact. However, it can also be spread through water, food, and contaminated surfaces. Norovirus is typically most associated with winter, and is often dubbed the “Winter Virus.” It usually maintains its grasp from November to April, with activity picking up in January.

While often considered a form of stomach flu, norovirus is not the flu. However, it is highly contagious and often spreads rapidly through schools, nursing homes, and cruise ships. Last month, 220 people aboard the Queen Mary II were stricken with norovirus during a Caribbean cruise.

A new strain typically appears every two or three years, the last being in 2009. The new strain´s appearance has coincided with a rise in influenza, possibly raising the perception that this year´s flu season is particularly worse than it may actually be.

Using the CaliciNet database, experts with the CDC gathered and examined norovirus strain data linked to outbreaks in 2012 in the US. Their results showed that GII.4 Sydney was the cause of 266 norovirus outbreaks reported in the three-month period.

"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," said Dr. Aron Hall, an epidemiologist with the CDC´s Division of Viral Diseases (DVD).

This makes up only a very small number of the 21 million Americans who contract norovirus-like bugs every year, but is still alarming. And it is not yet clear whether this strain is more likely to infect more people, or make the ones who do catch it more ill than in previous strains. But according to Hall, any time a new strain emerges, it has the potential to increase disease “because people haven't been exposed to it before, so they're more susceptible.”

“New norovirus strains often lead to more outbreaks but not always," revealed Dr. Jan Vinjé, director of CaliciNet. "We found that the new GII.4 Sydney strain replaced the previously predominant GII.4 strain."

Better surveillance techniques have led to earlier detection of norovirus strains in the US and other countries. Health experts and the general public are able to prevent infections and control outbreaks much more efficiently when new strains are identified early on.

Ian Goodfellow, a researcher at University of Cambridge in England, said norovirus is the “Ferrari of viruses” because of the speed at which it passes through large groups of people.

"It can sweep through an environment very, very quickly. You can be feeling quite fine one minute and within several hours suffer continuous vomiting and diarrhea," he told Mike Stobbe with ABC News.

With better detection methods, experts have been able to determine how the bug spreads so rapidly. They now know that norovirus is also the most common cause of food poisoning in the US. The virus is spread by infected food handlers who either have poor hygiene or none at all when it comes to washing their hands after using the bathroom.

There is neither a cure nor vaccine for norovirus. Those who become infected just have to ride it out for the few days that it lasts, and guard themselves against dehydration.

Researchers are working to create a vaccine for norovirus, but there is nothing out there yet. "I think in the next five to 10 years, probably closer to 10," Vinjé told USA Today.

"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," said Hall.