New norovirus bug sweeps nation

Elizabeth Weise, USA TODAY | USATODAY

As if this year's robust flu season weren't enough, the Centers for Disease Control and Prevention reports today that a new strain of the vomiting disease norovirus has reached the USA from Australia. Last month, the bug, which causes nausea, forceful vomiting, diarrhea and abdominal pain, accounted for 58% of outbreaks of norovirus nationally.

It's not clear whether this strain is more likely to infect people or make them more ill than previous strains, but according to Aron Hall, an epidemiologist with the CDC's division of viral diseases, 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."

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

"This year, that unfortunately coincides with an early increase in flu season," Hall said. Some people mistakenly call norovirus "stomach flu," but aside from timing, "there's no connection between them at all," he said.

Norovirus typically begins very suddenly and lasts one to three days. Most people recover without treatment, but some require rehydration with liquids or intravenous fluids. The disease is most severe in the elderly and can also hit young children hard. Every year, more than 21 million Americans become infected with acute stomach bugs, called gastroenteritis by doctors, and approximately 800 die, according to the CDC. Much of that is probably from norovirus, Hall said.

The new strain was first detected in Australia last March and has caused outbreaks in several other countries. From September through December, it was the leading cause of norovirus outbreaks in the USA, according to this week's Morbidity and Mortality Weekly Report from the CDC. Norovirus mutates rapidly, and new strains are common, typically showing up every two or three years, said Jan Vinjé, director of CaliciNet, an outbreak surveillance network for noroviruses in the USA.

Norovirus is extremely contagious. The best protection is vigilant hand washing with soap and water. If surfaces may have been contaminated, the CDC recommends disinfecting them with a diluted bleach solution made of five to 25 tablespoons of household bleach to a gallon of water.

Researchers are working to create a vaccine for norovirus, but nothing is ready for the market, Vinjé said. "I think in the next five to 10 years, probably closer to 10," he said.