Norovirus found in 4% of gastroenteritis patients at VA hospitals

PHILADELPHIA — Noroviruses were detected in 4% of the stool specimens collected within 7 days of symptom onset among patients with acute gastroenteritis presenting at four Veterans Affairs medical centers, according to data presented at IDWeek 2014.

The incidence of outpatient norovirus-associated gastroenteritis was 188 per 100,000 patients. The incidence of community-acquired norovirus among inpatients was 11 per 100,000 patients, and the incidence of hospital-acquired norovirus among inpatients was 54 per 100,000 patients.

“Noroviruses are increasingly recognized as a frequent cause of sporadic acute gastroenteritis disease and outbreaks,” Scott Grytdal, MPH, of the CDC, said during his presentation. “Norovirus-positive specimens followed a winter seasonal distribution, and strains were consistent with strains found in earlier studies conducted in this period and with novel strains associated with outbreaks reported during 2011-2012. Many outbreaks attributed to norovirus occur in health care settings, but this burden has not been well-documented.”

Grytdal and colleagues evaluated the incidence of norovirus acute gastroenteritis at four VA medical centers in Atlanta, Houston, Los Angeles and New York from November 2011 to October 2012, using stored stool specimens collected for diagnostic testing. They calculated the incidence of norovirus-associated acute gastroenteritis using administrative and patient population data for each center. The analysis included 1,160 specimens.

There were 375 community-acquired inpatient specimens, 582 hospital-acquired inpatient specimens and 203 outpatient specimens. Fifty of the specimens were positive for norovirus. There were seven norovirus genotypes detected, and the majority (84%) were genogroup II variants. The virus followed a seasonal pattern, with most cases (66%) being detected from November 2011 to March 2012.

“The estimated outpatient incidence was lower than other outpatient incidence estimates across the US and Europe,” Grytdal said. “Estimated community-acquired inpatient incidence is similar to earlier reports from the US and Europe. Hospital-acquired norovirus incidence is likely very sensitive to outbreaks of norovirus and additional data and research is needed to more completely ascertain incidence in health care facilities. Enhanced active surveillance using clear case definitions and specimen sampling schemes are needed to better define the disease burden in the VA population.” — by Emily Shafer

For more information:

Grytdal S. Abstract 1292. Presented at: IDWeek 2014; Oct. 8-12; Philadelphia.

Disclosure: The researchers report no relevant disclosures.