No difference found between hosts, pathogens and environmental settings
Norovirus infections—sometimes known as the stomach flu—typically last for the same amount of time, independent of age or the type of norovirus a person is infected with, according to a recent study by the University of Georgia College of Public Health, Emory University and the Centers for Disease Control and Prevention in the journal Epidemiology and Infection.
Symptoms from a norovirus infection last about two days, a finding that is constant between infected individuals, as well as environmental settings. The incubation period—or time until symptoms start—is also a consistent 1.5 days from time of infection. These findings differ from the authors’ expectations.
“I would have expected there to be a difference in something like a hospital setting or a difference depending on age groups,” said Andreas Handel, an assistant professor of epidemiology. “But when we analyzed the data, we didn’t see much of a difference.”
Norovirus infections lead to unpleasant and often severe gastrointestinal problems. The symptoms of a norovirus infection often include vomiting, nausea, diarrhea, and at times, dehydration, said Theresa Devasia, a third-year statistics major at UGA.
While infections tend to be most severe in the young and the old, it was not well known how the time between the infection and the onset of symptoms, as well as the duration of symptoms might depend on age and other characteristics.
Working on this study, Devasia and Handel studied a large set of outbreaks of norovirus infections. They went through past research in order to collect their data, searching for norovirus outbreaks and obtaining details about the patients, the setting, means of transmission and other relevant values.
“For instance, we looked at health care settings and food service settings to see if they might show differences,” Handel said.
They found that, on average, “if you get norovirus, 32 hours is on average how long it takes from being exposed to having symptoms and 44 hours is on average how long you have the symptoms—pretty much no matter what,” Handel said.
They also found that none of the characteristics they investigated showed a meaningful association with the duration of the time until symptoms show up and the duration of symptoms.
One caveat noted by the authors is that the data they analyzed was reported on the level of individual outbreaks, not individual patients. Future studies looking at individual patients are required to further test the findings.
Understanding the time it takes before symptoms start and the duration of symptoms is important for infection control methods, as well as for future computer modeling studies that are oftentimes used to evaluate the impact of a potential norovirus vaccine, which is currently in development.
Additional study co-authors are Ben Lopman of the CDC and Juan Leon of Emory University.
The journal article on “Association of host, agent and environment characteristics and the duration of incubation and symptomatic periods of norovirus gastroenteritis” is available at http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9456829.
– Sydney Devine
Posted March 9, 2015.