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Sapovirus: An Important Cause of Gastroenteritis Outbreaks

By Amesh A. Adalja, MD, FACP, April 27, 2012

Among the myriad causes of viral gastroenteritis, the highly contagious noroviruses are of chief concern, as they are responsible for outbreaks in institutional settings, on cruise ships, and in schools. However, in a subset of viral gastroenteritis outbreaks in which norovirus is not detected, the culprits may be astrovirus, adenovirus, and the vaccine-preventable rotavirus. Sapovirus, a pathogen discovered in 1977 from the same family as norovirus (Caliciviridae), is an underappreciated but important cause of norovirus-negative outbreaks. A recent paper in Emerging Infectious Diseases offers evidence of this with results of a study of gastroenteritis outbreaks over 7 years.

Outbreaks in Minnesota and Oregon

Between 2002 and 2009, public health officials in Oregon and Minnesota investigated more than 2,000 gastroenteritis outbreaks at various locations, including long-term care facilities, schools, prisons, and lodging facilities. Most were caused by norovirus (52%) and bacteria/parasites/other agents (22%).

Of the 7% of outbreaks that were negative for both norovirus and bacteria, 66% (93) were investigated more fully. PCR diagnostics indicated that 23% were caused by sapovirus. Further characterization of the sapovirus outbreaks revealed that 66% occurred in long-term care facilities and 10% in schools; 67% occurred in colder months; and 86% of infections involved person-to-person transmission.

Clinical symptoms included diarrhea (88%), vomiting (49%), and fever (23%), with median duration of 48 hours.

Expanded Diagnostic Testing Needed

Although not known to many clinicians, sapovirus appears to be responsible for a considerable proportion of viral gastroenteritis outbreaks in the U.S. This suggests a need for more routine diagnostic testing, which is now reserved primarily for gastroenteritis cases in which infection with Clostridium difficile or travel-related pathogens is suspected. Testing is not performed regularly, even though rotavirus and norovirus diagnostics are available.

Detailed information on the pathogens causing gastroenteritis could facilitate rapid outbreak detection, decrease antibiotic use for viral etiologies, and improve institutional infection control. Diagnostics also would elucidate gastroenteritis epidemiology and provide information that is vital in designing high-impact vaccines and antiviral agents.

Reference: Lee LE, Cebelinski EA, Fuller C, et al. Sapovirus outbreaks in long-term care facilities, Oregon and Minnesota, 2002-2009. Emerg Infect Dis 2012; 18:873-876.