Sapovirus is a growing concern in long-term care facilities

Sapovirus is a growing concern in long-term care facilities 

In a collaborative study between the Oregon Public Health Division, the Minnesota Department of Health, and the US Centers for Disease Control and Prevention (CDC), Lore E Lee, MPH, from the Oregon Public Health Division in Portland, and colleagues found that gastroenteritis in long-term care facilities (LTCFs) may be caused by sapovirus, an organism not routinely tested. The findings, published online 11 Apr 2012 in Emerging Infectious Diseases [Lee LE et al: Sapovirus outbreaks in long-term care facilities, Oregon and Minnesota, USA, 2002-2009. Emerg Infect Dis. 2012; 18(5); available at ] underscore the need for multiorganism testing during gastroenteritis outbreaks, as the exact etiology of the outbreak can be difficult to discern on the basis of clinical profile alone. 

Using data from the Oregon and Minnesota public health departments, the researchers investigated 2161 gastroenteritis outbreaks between 2002 through 2009. Of these, 142 outbreaks (7 percent) were found to be norovirus-negative, and 93 of these were further tested for other gastrointestinal viruses including sapovirus, astrovirus, adenovirus, and rotavirus. Sapovirus was identified in 21 outbreaks (23 percent), with 66 percent of these occurring in LTCFs. Close to half of these cases occurred in 2007 alone. Using data from 14 of the 21 outbreaks, for which clinical data on 141 to 269 patients were available, symptoms appeared to last from 24 to 105 hours (median duration, 48 hours), and the clinical profile included vomiting (49 percent), diarrhea (88 percent), and fever (23 percent). "4 (19 percent) of 21 sapovirus outbreaks were caused by sapovirus [genogroup I (GI)], 1 (5 percent) by sapovirus GII, 15 (71 percent) by sapovirus GIV, and 1 (5 percent) by sapovirus GV," the authors report. The clinical symptoms and outbreak settings were not statistically different among genogroups. 

The researchers note that the clinical findings are similar to the criteria used to evaluate norovirus outbreaks in settings where laboratory resources are limited. "We found, however, that sapovirus and norovirus outbreaks are clinically and epidemiologically similar enough to be indistinguishable without laboratory testing," write the authors.  The high proportion of sapovirus outbreaks among LTCFs may not represent a true distribution of sapovirus outbreaks in Oregon and Minnesota, discuss the authors. Rather, these findings may be artifactual as a result of legally mandated outbreak reporting by healthcare facilities. The authors note that the spike in sapovirus gastroenteritis cases in 2007 may have been part of a worldwide surge in gastroenteritis outbreaks that year; however, sapovirus infections among patients aged 65 years or older do appear to have been trending upward since 2002. The researchers acknowledge study limitations such as selection bias, possible underreporting from institutions where outbreak reporting is not legally mandated, and the fact that norovirus-positive samples were not tested for sapovirus, which may have led to sapovirus outbreaks being underestimated. "In keeping with recent recommendations, at minimum, adding sapovirus to routine diagnostics of infections that occur in any setting and by any mode of transmission will establish etiologies of some norovirus-negative outbreaks and help define the disease impact and clinical characteristics of sapovirus infections," conclude the authors. "These data can in turn be used to develop and evaluate sapovirus disease management guidelines and sapovirus outbreak prevention and control measures." 

 [Byline: Jennifer Garcia] -- Communicated by: ProMED-mail 

[The family _Caliciviridae_ contains 4 genera _Sapovirus_, _Norovirus_, _Lagovirus_, and _Vesivirus_, which include Sapo virus (SaV), Norwalk virus (NoV), Rabbit hemorrhagic disease virus (RHDV), and Feline calicivirus (FCV), respectively. SaV is a causative agent of gastroenteritis in children and adults. SaV can be divided into 5 genogroups (GI-GV), among which GI, GII, GIV, and GV are known to infect humans, whereas SaV GIII infects porcine species. Sapovirus was first detected in 1977 as the cause of a gastroenteritis outbreak in a home for infants in Sapporo, Japan, and was thereafter reported primarily among young children with acute gastroenteritis. After sapovirus diagnostic RT-PCR was developed, sapovirus outbreaks were discovered in LTCFs and other settings populated by adults. In their conclusions the authors note that: "In this study, the high (66 percent) proportion of sapovirus outbreaks in LTCFs among 21 outbreaks of previously unknown etiologies is likely to be an artifact of legally mandated outbreak reporting by health care facilities rather than the true distribution of sapovirus outbreaks in Oregon and Minnesota. Still, elderly residents of LTCFs are especially vulnerable to rapid transmission of viral enteric pathogens and serious complications from infection with these agents, and therefore merit the attention of public health." "Our data, together with a recent study in Canada, demonstrate that sapovirus has been circulating among the institutionalized elderly since at least 2002 and that sapovirus outbreaks increased in 2007 as part of a worldwide surge in gastroenteritis outbreaks. Before these retrospective studies, sapovirus infections among adults 65 years old and older had been reported as single cases at a low (3 percent) rate in 2002 and as nosocomial outbreaks in 2010 and 2005. Sapovirus outbreaks occurred in the same settings and had the same seasonal distribution as norovirus outbreaks. This study adds clinical details to information provided by studies in Canada and Europe. The clinical profile of sapovirus outbreaks in this study (49 percent vomiting, 88 percent diarrhea, and 23 percent fever, plus a median duration of 48 hours) approximates the criteria which are still used to evaluate norovirus outbreaks when laboratory resources are limited. However sapovirus and norovirus outbreaks are clinically and epidemiologically similar enough to be indistinguishable without laboratory testing." - Mod.CP