Every year, millions of people are infected with noroviruses - commonly called "stomach flu" - often resulting in up to 72 hours of vomiting and diarrhea.
While most people recover in a few days, the symptoms can lead to dehydration and - in rare cases, especially among the elderly and infants - death.
Now, researchers at the University of North Carolina School of Public Health have discovered that the virus mutates genetically, similar to the virus that causes influenza. And, like flu, a vaccine could be possible.
“One of the mysteries of medicine has been why do they keep infecting people when you'd think we'd be developing immunity,” said Lisa Lindesmith, one of the lead authors of the study, “Mechanisms of GII.4 Norovirus Persistence in Human Populations,” published today in the online medical journal PLoS Medicine. “What we've found is that the GII.4 arm [of the noroviruses] keeps changing. Whenever we're seeing big outbreaks of norovirus, we're also seeing genetic changes in the virus.”
Noroviruses are the leading cause of viral acute gastroenteritis. They are highly contagious, often causing epidemic outbreaks in families and communities, on cruise ships, in hospitals and in assisted living facilities. The viruses are especially hard on the elderly – in 2006, 19 deaths were associated with norovirus acute gastroenteritis in long-term care facilities in the United States. Often, infection can mean many miserable hours, with time lost from work, school and other activities. There is no treatment to stop the infection.
The virus, first isolated from an outbreak in an elementary school in Norwalk, Ohio, in 1968, is common worldwide. The researchers analyzed the relationship among the sequences of certain genes encoding the GII.4 norovirus strains that have been isolated over the past 20 years. They found that the virus evolved irregularly, and when new strains emerged, they often cause epidemic outbreaks.