Norovirus Is Now the Main Cause of Acute GI Problems in Kids

Yael Waknine

March 26, 2013

Norovirus has surpassed rotavirus as the leading cause of acute gastroenteritis among children younger than 5 years, according to new study results published in the New England Journal of Medicine.

Analyzing surveillance data for 3 US counties, Daniel Payne, PhD, MSPH, from the Centers for Disease Control and Prevention's (CDC's) National Center for Immunization and Respiratory Diseases in Atlanta, Georgia, and colleagues found that norovirus was responsible for 21% of acute gastroenteritis cases in 2009 and 2010; only 12% were attributed to rotavirus.

"This year has been an awful year for viruses in general, but now there's also a new norovirus — and as we saw with things like the H1N1 virus, I think we're feeling a big clinical impact; about 15% to 20% of what I'm seeing in the office every day is now stomach virus," Robert Dudley, MD, a pediatrician at Community Health Center, Inc, in Middletown, Connecticut, told Medscape Medical News in an interview. Although he does not test for particular viruses, the clinical picture matches that of the "new viral player in the mix, " said Dr. Dudley, who was not involved in the study.

On the basis of their new analysis, Dr. Payne and colleagues estimate the average annual numbers of US hospitalizations, emergency department visits, and outpatient visits due to norovirus infection for kids under 5 exceeded 14,000, 281,000, and 627,000, respectively, in 2009 and 2010. The estimated cost for care was more than $273 million in treatment costs each year.

The investigators collected data for 1295 children younger than 5 years who had been treated for acute gastroenteritis and whose samples had been laboratory tested at 1 of 3 centers that form the New Vaccine Surveillance Network: the University of Rochester Medical Center in Monroe County, New York; Vanderbilt University Medical Center in Davidson County, Tennessee; or Cincinnati Children's Hospital Medical Center in Hamilton County, Ohio. They also included data from 493 healthy control individuals seen for well-child visits.

Overall, 21% of children with acute gastroenteritis — 22% in 2009 and 20% in 2010 — tested positive for norovirus, compared with 4% of control individuals, indicating a low rate of asymptomatic infection.

Nearly half (47%) of infections occurred in children aged 6 to 18 months (mean age, 17.0 months; median, 14 months); the peak period for symptom onset was January for both years.

Of 147 samples available for genotyping in 2009, 142 (97%) showed infection with genogroup GII, and 5 (3%) with GI. Although the majority of illnesses were caused by GII.4 variants in both years, the predominant strain shifted from GII.4 Minerva (2006b) in 2009 (71%) to GII.4 New Orleans (35%) in 2010, as determined on the basis of 100 samples available for genotyping that year.

Despite this transition, the annual norovirus disease burden remained consistent (per 10,000 children in 2009 and 2010: hospitalizations, 8.6 and 5.8; emergency department visits, 146.7 and 134.3; outpatient visits, 367.7 and 260.1). The authors note that the GII.4 strain has been implicated as the leading cause of outbreaks worldwide.

"As compared with other genotypes of norovirus, GII.4 norovirus is shed in larger numbers during infection, causes more severe symptoms with greater likelihoods of transmission and poor outcomes, and may bind to multiple distinct histo–blood group antigens, which serve as norovirus-binding ligands on mucosal surfaces," the authors write. They add that developing an efficacious vaccine may be complicated by the anticipated emergence of new variants on a "regular basis."

The study was supported by a cooperative agreement with the CDC. Dr. Payne and Dr. Dudley have reported no relevant financial relationships. Study coauthors have disclosed relationships with GlaxoSmithKline, Merck, and Luminex Molecular Diagnostics.

N Engl J Med. 2013;368:1121-1130. Abstract

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