Environmental Swabs as a Tool in Norovirus Outbreak Investigation, Including Outbreaks on Cruise Ships

Abstract

In this study, we investigated whether environmental swabs can be used to demonstrate the presence of norovirus in outbreak settings. First, a procedure was set up based on viral RNA extraction using guanidium isothiocyanate buffer and binding of nucleic acids to silica. Subsequently, environmental swabs were taken at 23 Dutch restaurants and four cruise ships involved in outbreaks of gastroenteritis. Outbreaks were selected based on clinical symptoms consistent with viral gastroenteritis and time between consumption of suspected food and onset of clinical symptoms (>12 h). Norovirus RNA was demonstrated by real-time reverse transcriptase PCR in 51 of 86 (59%) clinical specimens from 12 of 14 outbreaks (86%), in 13 of 90 (14%) food specimens from 4 of 18 outbreaks (22%), and in 48 of 119 (40%) swab specimens taken from 14 of 27 outbreaks (52%). Positive swab samples agreed with positive clinical samples in seven outbreaks, showing identical sequences. Furthermore, norovirus was detected on swabs taken from kitchen and bathroom surfaces in five outbreaks in which no clinical samples were collected and two outbreaks with negative fecal samples. The detection rate was highest for outbreaks associated with catered meals and lowest for restaurant-associated outbreaks. The use of environmental swabs may be a useful tool in addition to testing of food and clinical specimens, particularlywhen viral RNA is detected on surfaces used for food preparation.

Norovirus outbreaks on commercial cruise ships: a systematic review and new targets for the public health agenda

“…Food testing was reported in five studies (Morillo et al 2012;Verhoef et al 2008a, b;Boxman et al 2009;Koo et al 1996) for a total of 11 outbreaks (data not shown). Environmental swabs were collected only in the outbreaks described by Boxman et al 2009;Koopmans et al 2006;Takkinen 2006;Verhoef et al 2008a, b (data not shown). Real time-polymerase chain reactions (RT-PCRs) were performed in 56 out of 70 vessels involved, and in 50 of them, the genotype of the NoV was detected.…”

“…Thirteen of these were subsequently excluded because they did not meet the inclusion criteria: five because they were reports of outbreaks on military ships, and eight because data about the location and the characteristics of the outbreak were not available. Twenty-two articles (Morillo et al 2012;Wikswo et al 2011;Vivancos et al 2010;Xerry et al 2009;Boxman et al 2009;Xerry et al 2008;Chimonas et al 2008;Verhoef et al 2008a, b;Takkinen 2006;Koopmans et al 2006;Ferson and Ressler 2005;Isakbaeva et al 2005;Widdowson et al 2004;Gallimore et al 2003;CDC 2002;Minooee and Rickman 1999;McEvoy et al 1996;Koo et al 1996;Herwaldt et al 1994;Khan et al 1994) met the inclusion criteria and were thus included in our review.…”

“…Stool samples and/or serum specimens from ill passengers were collected by medical personnel aboard cruise ships and tested for laboratory confirmation in all studies, with the only exception of the study by Morillo et al in which only the food was tested (Morillo et al 2012). Food testing was reported in five studies (Morillo et al 2012;Verhoef et al 2008a, b;Boxman et al 2009;Koo et al 1996) for a total of 11 outbreaks (data not shown). Environmental swabs were collected only in the outbreaks described by Boxman et al 2009;Koopmans et al 2006;Takkinen 2006;Verhoef et al 2008a, b (data not shown).…”

“…Food testing, however, was carried out in few studies, while the acquisition of environmental swabs was described only in a group of outbreaks that occurred in Europe in 2006. This is understandable given that the environmental swab is considered a complementary tool to fecal and food testing (Boxman et al 2009), and that food samples are usually difficult to obtain because of a delay in the execution of these procedures. This delay is one of the main reasons why the primary source of an outbreak often goes undetected.…”

Norovirus GII.4 Detection in Environmental Samples from Patient Rooms during Nosocomial Outbreaks

“…The significance of such contamination is strongly indicated in reports in which NoV RNA was detected in environmental samples from hospitals (13), cruise ships (14,15), restaurants (16), and houseboats (17) during recurring or ongoing outbreaks. The high viral load in vomitus and feces (7), low infectious dose (18), and short-term immunity (19) that typify NoV gastroenteritis increase the risk of prolonged outbreaks and environmental spread in semiclosed units, in which strains of NoV genotype II.4 (GII.4) or GII.3 tend to dominate (20).…”