Role of fomite contamination during an outbreak of norovirus on houseboats

An outbreak of suspected norovirus gastroenteritis among three consecutive groups of houseboaters on a large recreational lake in Arizona was investigated to assess the role of fomite contamination, and to provide recommendations for prevention of future outbreaks. Interior boat surfaces were sampled for norovirus using transport swabs. Onboard toilet reservoirs were swabbed as a surrogate for stool samples from ill participants, since none were available, and onboard potable water supplies were sampled for norovirus. All samples were analyzed using RT-PCR with primers specific for human norovirus. Widespread fomite contamination was documented in the houseboats; 83% (5/6) of bathroom surface samples, 40% (2/5) of kitchen surface samples, and 100% (3/3) of doorknob samples were positive for the presence of norovirus. Samples of onboard potable water supplies were all negative. One of the participants on the first boating trip arrived already displaying symptoms of gastrointestinal illness prior to boarding the boat. This investigation demonstrates the potential role of widespread fomite contamination in outbreaks in confined spaces. To prevent or minimize future outbreaks in confined spaces, the adoption of practices such as surface disinfection and the utilization of methods to identify and exclude those with gastroenteritis from trips or activities in confined spaces, where others may become infected, are recommended.     

Waterborne outbreak of gastroenteritis in a religious summer camp in Norway, 2002

In July 2002 an outbreak of acute gastroenteritis occurred in a camp facility in western Norway during a 10-day seminar, with around 300 guests staying overnight and several day-time visitors. Environmental and epidemiological investigations were conducted to identify and eliminate the source of the outbreak, prevent further transmission and describe the impact of the outbreak. Of 205 respondents, 134 reported illness (attack rate, 65%). Multivariate analysis showed drinking water and taking showers at the camp-site to be significant risk factors. Secondary person-to-person spread among visitors or outside of the camp was found. Norovirus was identified in 8 out of the 10 stool samples analysed. Indicators of faecal contamination were found in samples from the private untreated water supply, but norovirus could not be identified. This outbreak investigation illustrates the importance of norovirus as a cause of waterborne illness and the additional exacerbation through person-to-person transmission in closed settings. Since aerosol transmission through showering contributed to the spread, intensified hygienic procedures such as isolation of cases and boiling of water may not be sufficient to terminate outbreaks with norovirus.     

1起疑似食源性诺如病毒感染暴发疫情的流行病学调查

摘要:目的 调查1起小学内出现多名急性胃肠炎病例的感染事件,提出预防控制措施。方法 按照病例定义开展病例搜索,采用描述性流行病学方法和病例对照研究方法进行分析;样本采用RT-PCR方法进行肠道病毒核酸检测。结果 武进区某小学2015年3月2日-11日,出现149例以呕吐症状为主的学生,罹患率为9.0%,3月2日出现发病高峰,病例发病急、班级分布广。现场采集患者肛拭子或呕吐物、对照及食堂工作人员肛拭子、食物和环境样本等共42份,其中2名患者肛拭子、2名患者呕吐物及1名食堂工作人员肛拭子检测出诺如病毒GII型。结论 这是1起由诺如病毒GII型引起的急性胃肠炎暴发疫情,暴发原因可能是由带毒食堂工作人员污染部分食物所致,以食源性传播为主。     

Infection of staff during an outbreak of viral gastroenteritis in an elderly persons' home

An outbreak of viral gastroenteritis in an elderly persons' residence is reported. Seventeen of 37 (47%) residents and 22 of 50 (44%) staff developed illness. Adenovirus was seen by direct electron microscopy in two vomitus and two faeces specimens. It is suggested that the most likely mode of transmission was environmental contamination by vomitus.     

A gastroenteritis outbreak due to norovirus associated with a Colorado hotel

Describing the system components of norovirus outbreaks is important in understanding how to prevent future outbreaks. Investigation of these components includes environmental, epidemiologic, and laboratory perspectives. This study describes how an investigation from these three perspectives was conducted and the significance of each component in understanding norovirus outbreaks. On May 23, 2000, members of a professional group attending two meetings at a local hotel in Englewood, Colorado, began to complain of gastrointestinal illness. Sixty-nine illnesses were reported among 133 attendees. Eight hotel employees also complained of illness. Staff from the Tri-County Health Department and the Centers for Disease Control and Prevention investigated the outbreak. Three stool specimens collected from ill attendees contained norovirus. While the epidemiologic component did not identify a specific vehicle of transmission, the environmental investigation revealed food-handling practices, food handler perceptions, and hotel policies that may have contributed to disease transmission.     

苏州市14起诺如病毒胃肠炎暴发疫情流行特征分析

目的了解苏州市诺如病毒胃肠炎暴发疫情的流行病学特征。方法对2010-2014年发生的14起诺如病毒胃肠炎暴发疫情进行描述性流行病学分析,采用聚合酶链反应对病例肛拭子、粪便、呕吐物、水、环境涂抹标本进行核酸检测。结果 2011-2014年,苏州市共报告14起诺如病毒胃肠炎暴发疫情,罹患率波动范围为0.89%~21.18%。14起疫情中12起(85.71%)发生于托幼机构和中小学校,医院、农村各1起。全年均有发生,但以寒冷季节发生较多。仅1起查明与二次供水受到污染有关,13起未证实暴发原因。核酸检测结果12起由诺如病毒GII基因组引起,2起由GI基因组引起。结论诺如病毒已成为苏州市急性胃肠炎暴发疫情的重要病原,托幼机构和学校是高发场所,GII基因组是主要基因组。在暴发疫情处理中,应加强传染源和传播途径的调查。     

Multiple norovirus outbreaks among workplace canteen users in Finland, July 2006

Multiple gastroenteritis outbreaks occurred between 25 and 31 July 2006 in 10 workplace canteens in south-western Finland. One vegetable processing plant provided raw vegetables to all the canteens. We conducted cohort studies in the three most visited canteens and environmental investigations in the kitchens and the plant. Patients' stools, food, water and environmental samples were tested for enteric bacteria and viruses. Of the three canteens, 150/273 respondents (response rate 82%) had gastroenteritis. Consumption of mixed raw vegetables was significantly associated with the illness but no single vegetable explains the outbreak. An identical norovirus GII.1 genotype was detected from all genotyped patient samples. Water, food, and environmental samples were negative for norovirus. The facilities had appropriate hygienic conditions and no staff member had gastroenteritis prior to the outbreak. Tracing back the vegetables to the farm level proved unsuccessful. This was the largest foodborne norovirus outbreak in Finland.     

A norovirus outbreak associated with consumption of NSW oysters: implications for quality assurance systems

Norovirus is a common cause of gastroenteritis outbreaks associated with raw shellfish consumption. In Australia there have been several reports of norovirus outbreaks associated with oysters despite the application of regulatory measures recommended by Food Standards Australia New Zealand. This study describes an outbreak of norovirus gastroenteritis following the consumption of New South Wales oysters. In September 2007, OzFoodNet conducted a cohort study of a gastroenteritis outbreak amongst people that had dined at a Port Macquarie restaurant. Illness was strongly associated with oyster consumption, with all cases having eaten oysters from the same lease (RR undefined, p < 0.0001). Norovirus was detected in a faecal specimen. Although no pathogen was identified during the environmental investigation, the source oyster lease had been closed just prior to harvesting due to sewage contamination. Australian quality assurance programs do not routinely test oysters for viral contamination that pose a risk to human health. It is recommended that the feasibility of testing oysters for norovirus, particularly after known faecal contamination of oyster leases, be assessed.     

A large-scale gastroenteritis outbreak associated with Norovirus in nursing homes

An increase in gastroenteritis outbreaks due to Norovirus has been reported worldwide. We investigated a large-scale outbreak affecting 246 residents and 33 staff members in six nursing homes in the Tel-Aviv district, Israel, during 3 weeks in 2002. Person-to-person spread was noticed in all nursing homes. The spread of disease could not be attributed to social interactions. Among the elderly residents, the hospitalization rate was 10.2% and the case-fatality rate was 2.0%. Bacteriological cultures were negative. Overall, 7 out of 15 stool specimens were positive for Norovirus by RT-PCR. All were sequenced and found to be 90% identical. The characteristics of this outbreak and the RT-PCR results suggest that illness was caused by Norovirus. Due to the high case-fatality rate of Norovirus gastroenteritis, there should be a high index of suspicion when encountering a gastroenteritis outbreak among the elderly. This will enable prompt action to stop the spread of illness.     

Norovirusinfektionen in Deutschland

Noroviruses are responsible for the majority of acute viral gastroenteritis infections worldwide. Transmission may be faecal-oral or through contaminated food and water or airborne by virus-containing aerosols. Characteristics of noroviruses that facilitate their spread are their high concentration in stool and vomitus, their extreme environmental stability, their low infectious dose as well as the lack of long-lasting immunity. The majority of norovirus infections occur in large outbreaks among persons living in institutional settings, such as hospitals and nursing homes, although sporadic cases also occur. Children and elderly persons are most often affected. Illness is characterized by acute onset of projectile vomiting. For prevention and control of norovirus outbreaks strict control management is necessary. Based on the high genomic variability new variant noroviruses with different pathogenic factors can arise. Depending on the circulating variant the extent of the usual winter peak can vary enormously. Available diagnostic methods include RT-PCR assays for detection of viral RNA, electron microscopy and enzyme immunoassays (EIA) for detection of viral antigens. The implicated virus can be subtyped through nucleotide sequencing and linked to a specific outbreak. With the enactment of the Protection against Infection Act in January 2001 a mandatory reporting system of norovirus infections was established. Analysis of surveillance data from this system permits a detailed overview of the nationwide epidemiology of this disease in Germany.     

Foodborne Snow Mountain agent gastroenteritis with secondary person-to-person spread in a retirement community

A variety of small round-structured viruses are being recognized with increasing frequency as a cause of gastroenteritis in the community, but have rarely been reported to cause outbreaks in hospitals or extended-care facilities. From March 20 through April 15, 1988, an outbreak of gastroenteritis occurred in a retirement facility in the San Francisco Bay area. Illness was characterized by diarrhea, nausea, and vomiting; two residents died. Attack rates were 46% (155 of 336) in residents and 37% (28 of 75) in employees. During the initial outbreak period, illness among residents was associated with two shrimp meals served in the facility dining hall (odds ratio = 6.7). Person-to-person transmission probably occurred: The risk of becoming ill one or two days after a roommate became ill was significantly greater than that of becoming ill at other times during the outbreak (risk ratio = 6.5). Microbiologic examinations for bacterial and parasitic enteric pathogens were negative; however, 27-nm viral particles were detected by immune electron microscopy and by blocking enzyme immunoassay to Snow Mountain agent in stools obtained at the onset of illness from one of six ill residents. Seroconversion (greater than fourfold antibody rise) to Snow Mountain agent was detected in acute- and convalescent-phase serum specimens from five of six ill residents as measured by enzyme immunoassay, but not for Norwalk agent as measured by radioimmunoassay. This report of an outbreak of Snow Mountain agent gastroenteritis in an extended-care facility documents that these difficult-to-identify 27-nm viruses can cause outbreaks in inpatient settings.     

A large hotel outbreak of Norwalk-like virus gastroenteritis among three groups of guests and hotel employees in Virginia

A large outbreak of acute gastroenteritis occurred among three different groups of guests and the employees of a Virginia hotel within a 2-week period in November 2000. At least 76 of the hotel's guests and 40 hotel employees had acute gastroenteritis during this period. All tested ill persons were infected with the same strain of Norwalk-like virus, as shown by cloning and sequencing of virus detected in stool specimens from the three guest groups and the employees. Epidemiologic investigation suggested food as the probable source for the guests. Most of the employees, including those sick, did not eat in the hotel, suggesting that environmental contamination and person-to-person transmission could have contributed to the outbreak. The disease continued to spread in the hotel, passing from one guest group to another, by food, environmental contamination, and/or by person-to-person transmission through infected employees and guests. The study describes procedures implemented to control the outbreak and makes recommendations for future outbreak control.     

A large outbreak of campylobacteriosis associated with a municipal water supply in Finland

In August 1998, an outbreak of campylobacteriosis occurred in one municipality in northern Finland. A 10% random sample of residents (population 15 000) was selected through the National Population Registry for a survey conducted by using postal questionnaires. Cases were defined as residents of the municipality with onset of acute gastroenteritis from 1 to 20 August 1998. Of 1167 respondents (response rate 78%), 218 (18.7%) met the case definition. Drinking non-chlorinated municipal tap water was strongly associated with illness (OR 34.4). The estimated total number of ill persons was 2700. Campylobacter jejuni was isolated from stool samples of 45 (61%) out of 74 patients tested. All five isolates tested had indistinguishable PFGE patterns. Water samples were negative for campylobacter and coliforms. Epidemiological and environmental evidence suggested mains repair as the source of contamination. Non-chlorinated ground-water systems may be susceptible to contamination and can cause large outbreaks.     

Outbreaks of noroviral gastroenteritis in Florida, 2006-2007

Noroviruses are an important cause of sporadic cases and outbreaks of acute gastroenteritis. During 2006-2007, widespread increases in acute gastroenteritis outbreaks consistent with norovirus were observed in the United States. We conducted a statewide survey to characterize norovirus outbreak activity in Florida during a 1-year period. From July 2006 to June 2007, 257 outbreaks of norovirus gastroenteritis were identified in 39 of Florida's 67 counties. About 44% of outbreaks were laboratory confirmed as norovirus and 93% of these were due to genogroup GII. About 63% of outbreaks occurred in long-term care facilities and 10% of outbreaks were classified as foodborne. The median number of ill persons per outbreak was 24, with an estimated total of 7880 ill persons. During the study period, norovirus outbreak activity in Florida was widespread, persistent, and consistent with increased activity observed in other parts of the country.     

Notes from the field: outbreaks of rotavirus gastroenteritis among elderly adults in two retirement communities--Illinois, 2011

In February 2011, three residents of a retirement community in Illinois were hospitalized for acute gastroenteritis. The admitting physicians ordered testing of stool specimens for several pathogens, including rotavirus. The hospital laboratory detected rotavirus antigen in specimens from each patient, and the hospital infection control practitioner reported that information to the Cook County Department of Public Health. Two additional residents were hospitalized for rotavirus gastroenteritis shortly thereafter. The health department sent stool specimens from the five patients to CDC for testing for rotavirus and norovirus. Rotavirus was detected in each specimen; norovirus was not detected. During a subsequent investigation, all available residents were queried regarding recent diarrheal symptoms. Preliminary data indicated that 22% of residents had confirmed or probable rotavirus disease and 10 residents were hospitalized. In May 2011, another outbreak of rotavirus gastroenteritis was detected at a second retirement community in the county. On preliminary analysis, the overall attack rate in the second retirement community was 11%, and 20 residents were hospitalized. No deaths were identified in either outbreak. Based on preliminary results of the investigations and general knowledge of rotavirus transmission, within each community, rotavirus likely was transmitted from person to person via contaminated hands or fomites (e.g., environmental surfaces). The outbreaks lasted ≥4 weeks.     

An outbreak of acute infectious nonbacterial gastroenteritis in a high school in Maryland

An outbreak of acute infectious nonbacterial gastroenteritis (AING) occurred in a high school in Maryland in 1984. Thirty-six percent of students surveyed met the case definition of gastroenteritis, as did 24 percent of school employees. Eating lunch in the cafeteria on January 30 was significantly associated with illness. After controlling for other food items consumed during the January 30 lunch, only the sandwiches were significantly associated with illness, but the source of the contamination was not identified. Four of 17 serum pairs from sick students and none of the 8 serum pairs from exposed controls (a nonsignificant difference) showed at least a 4-fold rise in antibody titre to Norwalk virus between acute- and convalescent-phase specimens. This outbreak of AING is believed to be the first to implicate epidemiologically sandwiches as vehicles of transmission. The outbreak highlights the need for investigators to look for a viral etiology in gastroenteritis outbreaks.