A majority of traveler's diarrhea cases among U.S.
travelers to Mexico and Guatemala were attributed to
norovirus, a common cause of nonbacterial gastroenteritis
outbreaks usually associated with developed countries,
according to a study by researchers at the Bloomberg School
of Public Health and other institutions. The researchers
also found that the longer travelers stayed at their
destination, the more likely they were to contract
norovirus infections. The study was published in the
Journal of Clinical Microbiology.
"Noroviruses are known to be a major cause of food and
waterborne gastroenteritis outbreaks in domestic and unique
settings, such as cruise ships, and also have been
documented among military groups during deployment
overseas. However, few studies have investigated the
prevalence of norovirus infection among civilians traveling
from industrialized to developing countries," said Kellogg
J. Schwab, corresponding author of the study and an
assistant professor in the
Department of Environmental Health Sciences.
Noroviruses often are not considered in studies of
traveler's diarrhea, he said, because until recently
molecular detection methods for these viruses have not been
readily available.
The researchers examined stool samples from 34
individuals who experienced traveler's diarrhea during
trips to Antigua, Guatemala or Cuernavaca, Mexico, for
noroviruses, as well as for bacterial and protozoan
pathogens. Sixty-five percent of the individuals in the
study had at least one stool sample positive for
norovirus.
Although norovirus previously has been implicated as a
cause of traveler's diarrhea among visitors to Mexico, this
is the first study to indicate that norovirus contributes
to traveler's diarrhea in visitors to Guatemala.
Amy R. Chapin, first author of the study and a
doctoral candidate in the Department of Environmental
Health Sciences at the Bloomberg School, noted that 11
norovirus-positive stool samples also were positive for E.
coli, a leading bacterial cause of traveler's diarrhea,
thus indicating that dual infections among individuals
experiencing traveler's diarrhea may be more common than
previously thought.
The authors said that further research into the role
of noroviruses in traveler's diarrhea is warranted. The
simple, inexpensive molecular diagnostic techniques used in
this study to identify norovirus-positive stool samples
could serve to facilitate future norovirus-related research
in developing countries.
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