Norovirus identification important as vaccination reduces rotavirus disease burden

Norovirus was the second most common agent implicated in acute sporadic episodes of gastroenteritis in children aged younger than 5 who required hospitalization for their illness, data collected between January 2005 and January 2008 at the Universitary Hospital in Albacete, Spain indicated.

“Clinical and epidemiological characteristics of norovirus severe infection in children are not so well established and identifying the clinical profile of this infection would be useful because of the absence of rapid and widely-available detection methods in clinical laboratories,” Junquera et al wrote.

The researchers detected norovirus in 17.3% of the 221 study participants with viral gastroenteritis using reverse transcription polymerase chain reaction assays. They noted the following characteristics:

• Rotavirus remained the most frequent gastroenteritis pathogen at 45.7%.
• Norovirus was present in 52.5% of 32 patients with mixed infections and was identified as a single etiological pathogen in 8.2% of patients.
• Norovirus was frequently associated with a nosocomial source, accounting for 17.2% children who had norovirus gastroenteritis (n=29) and 17.6% of patients who had norovirus-rotavirus coinfection (n=17).
• Norovirus gastroenteritis was less severe than illness caused by rotavirus in terms of median severity score, proportion of severe episodes and percentage of infants that required IV rehydration.
• The most common clinical symptoms were vomiting (69%, n=20) and fever (48.3%, n=14).
• Duration of hospitalization was similar at around 3.5 days for patients with gastroenteritis caused by either norovirus or rotavirus.
• Norovirus affected mostly children aged younger than 2 years (75.8%, n=22).

Although norovirus infection peaked in November through February, the researchers cautioned that this may be due to the high prevalence of rotavirus-norovirus coinfection. Data indicated that norovirus was present during every month of the year with the exceptions of March and July.

“Rotaviruses are the major etiologic pathogens causing severe gastroenteritis in children, but in recent years noroviruses have been increasingly identified as relevant etiologic agents among hospitalized children in Europe, Asia and America and the relative importance of them may increase with rotavirus vaccination,” the researchers wrote. – by Nicole Blazek

Junquera CG et al. Pediatr Infect Dis J. 2009;28:604-607.

Noroviruses are the principal definable causes of foodborne and waterborne disease in most regions where they have been sought. There are only a few studies looking at the importance of noroviruses in children with endemic diarrhea. This study suggests that this group of viruses commonly cause pediatric diarrhea in this region of Spain. The role of noroviruses in mixed infections is uncertain and needs additional study.

– Herbert L. DuPont, MD

St. Luke’s Episcopal Hospital, Houston

Norovirus is an increasingly recognized pathogen, and what we see in Spain is a reflection of other countries including ours.

– Paul Offit, MD

Infectious Diseases in Children Editorial Board