A community waterborne gastroenteritis outbreak: evidence for rotavirus as the agent.

A community waterborne nonbacterial gastroenteritis outbreak occurred in Eagle-Vail, Colorado in March 1981. Illness (defined as vomiting and/or diarrhea) was statistically associated with water consumption (chi 2 for linear trend = 7.07, p less than .005). Five of seven persons associated with the outbreak were infected with rotavirus as shown by virus detection or serological methods. Bacterial pathogens, Giardia lamblia, and Norwalk virus were excluded as responsible agents. Rotavirus should be looked for as a cause of waterborne outbreaks.     

Role of Norwalk virus in two foodborne outbreaks of gastroenteritis: definitive virus association

Two separate food-associated outbreaks of gastroenteritis occurred among Erie County, New York residents in June 1986. In one outbreak, cases of illness were estimated to have occurred in 50% of the approximately 700 persons in 13 groups who ate at an out-of-county restaurant during a seven-day period, and, in the second outbreak, illness occurred in 26 (30%) of 87 persons who attended a graduation party held in a private home. Laboratory investigation included serology (blocking radioimmunoassay) to determine seroconversion to Norwalk virus and an enzyme immunoassay for detection of Norwalk virus antigen in stools, which the investigators have found to be more specific for Norwalk virus than serology. Seroconversion to Norwalk virus occurred in 11 (79%) of 14 restaurant-related cases and seven (100%) of seven graduation party cases. Seroconversion to Norwalk virus antigen was also found in four (40%) of 10 food handlers at the restaurant and in two (100%) of two food handlers at the graduation party. Antigen was detected in the stools of three (20%) of 15 restaurant-related cases and four (67%) of six graduation party cases. No stools for viral analyses were available for testing from food handlers. All seven of the patients with Norwalk virus-positive stools were also positive by seroconversion. Widespread availability of reagents for stool antigen detection would result in confirmation of more outbreaks due to Norwalk virus and in a more timely manner.     

实时荧光PCR检测诺瓦克病毒的应用研究

目的应用实时荧光PCR方法对诺瓦克病毒性急性胃肠炎进行快速检测，为疾病预防控制提供准确可靠的实验诊断依据。方法采集一起急性胃肠炎暴发流行患者的1份粪便、5份肛拭和1份呕吐物，进行实时荧光PCR检测。结果实时荧光PCR检测有1份病人粪便和1份病人肛拭样本中诺瓦克病毒核酸呈阳性。结论这是一起由诺瓦克病毒感染引起的急性胃肠炎暴发流行。     

A large outbreak of gastroenteritis associated with a small round structured virus among schoolchildren and teachers in Japan

In March 1989 a large outbreak of acute gastroenteritis occurred simultaneously among schoolchildren and teachers at nine elementary schools in Toyota City, Japan. Illness was observed in 3236 (41.5%) of 7801 schoolchildren and 117 (39.4%) of 297 teachers. The main clinical symptoms were diarrhoea, vomiting, nausea and abdominal pain. Gastroenteritis was significantly associated with the consumption of school lunch served by one particular lunch preparation centre. One food handler at the centre suffered from gastroenteritis during the outbreak. Small round structured virus (SRSV) was detected in 4 of 8 stool specimens from sick persons. The school lunch contaminated by the infected food handler is the most probable source of this outbreak due to SRSV.     

Norwalk-like gastroenteritis epidemic in a Toronto hospital.

An epidemic of gastroenteritis in a teaching hospital affected 57 patients and 69 staff over a 26-day period. The index case was a patient admitted with acute abdominal pain and diarrhea two days prior to the outbreak. The epidemic curve indicated person-to-person transmission. The incubation period, duration and types of symptoms were typical of Norwalk gastroenteritis, and Norwalk-like virus particles, serologically different from the prototype Norwalk virus strain, were observed in 17 of 20 fecal specimens examined by immune-electron microscopy.     

Risk factors for secondary transmission in households after a common-source outbreak of Norwalk gastroenteritis

In November 1984, a foodborne outbreak of Norwalk gastroenteritis occurred in a K-12 public school in northern Vermont. The outbreak offered an opportunity to systematically study in detail secondary transmission rates in households. Eating salad at Tuesday's school-sponsored Thanksgiving Banquet was associated with illness among students and staff members (p less than 0.025). Seven of 11 serum pairs from ill persons showed a fourfold or greater rise in antibody titer to Norwalk virus compared with one of nine controls (p = 0.028). The study of secondary household transmission revealed that households with persons with primary illness were 5.5 times more likely to experience secondary illness than households with well school children or adults. As the number of individuals with primary illness in the household increased, the secondary illness rates increased. Pre-school children were twice as likely as adults to develop secondary illness.     

25- to 30-nm virus particle associated with a hospital outbreak of acute gastroenteritis with evidence for airborne transmission

Between November 1 and 22, 1985, an outbreak of acute, nonbacterial gastroenteritis occurred in a 600-bed hospital in Toronto, Ontario, Canada. Illness in 635 of 2,379 (27%) staff was characterized by fatigue, nausea, diarrhea, and vomiting and had a median duration of 24-48 hours. The finding of virus-like particles measuring 25-30 nm in six stool specimens and low rates of seroresponse to Norwalk virus (3/39) and Snow Mountain agent (1/6) suggest that a Norwalk-like virus was responsible for the outbreak. The outbreak was of abrupt onset and high incidence, affecting 79 people in a single day. No common food or water exposure could be identified. The attack rate was greatest (69%) for staff who had worked in the Emergency Room. Of 100 patients and their companions who visited the Emergency Room on November 11-12 for unrelated problems, 33 (33%) developed gastroenteritis 24-48 hours after their visit, versus 0 of 18 who visited the Emergency Room on November 8 (p less than 0.001). An analysis of housekeepers who worked at least once during the period from November 9-13, which included those who became ill during the period of November 9-14, showed that the risk of becoming ill was four times greater for those who visited or walked through the Emergency Room than for those who did not (p = 0.028). These data are consistent with the possibility of the airborne spread of a virus.     

某市首起水源污染引起的诺瓦克病毒胃肠炎暴发的调查

目的调查分析某市429人出现以呕吐为主的群发性急性胃肠炎的原因,探讨区县生活饮用水卫生监督对策。方法现场流行病学调查与现场卫生学进行调查,应用ELISA、RT-PCR法对病例及水样标本进行实验室检测。结果采集的水厂A出厂水、末梢水及生活污水水体标本中,RT-PCR法检出诺瓦克病毒核酸阳性;现场调查发现水源受排污口污水污染,水厂卫生管理情况较差,水处理工艺较落后。结论这是某市首起水源污染引起的诺瓦克病毒所致的急性胃肠炎暴发事件,提示卫生监督部门应重点加强基层生活饮用水水源水监管力度,加强出厂水与末梢水的监测,提高水厂卫生管理水平,改进区县水厂水处理工艺。     

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.     

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.     

Norwalk virus gastroenteritis following raw oyster consumption

In January, 1980, six out of 13 persons (46%) attending a party in a small northwest Florida town near the Gulf of Mexico became ill with Norwalk virus gastroenteritis after eating raw oysters. Symptoms experienced by the ill persons were principally nausea (100%), vomiting (83%) and diarrhea (50%) and were of brief duration. The symptom complex and epidemiology of Norwalk virus infection closely resemble the gastrointestinal illness commonly referred to as the 24-hour intestinal flu or "stomach flu." Norwalk virus infection was identified in this outbreak by application of a recently developed sensitive and specific serologic radioimmunoassay. Oysters from the incriminated batch had fecal coliform levels above recommended standards; however, recent studies of oyster-harvesting waters have shown only a weak correlation between fecal coliforms and the presence of enteric viruses. Further studies are needed to determine whether modifications of monitoring modalities for oyster-harvesting waters are needed.     

Norwalk-related viral gastroenteritis due to contaminated drinking water

An explosive outbreak of gastrointestinal illness clinically compatible with infection by an agent serologically related to Norwalk virus agent occurred in an elementary school in May 1978. Seroconversion by radioimmunoassay to the Norwalk antigen was noted in two of three ill persons, but no viral particles were identified in stool. Illness developed in 72% of students and teachers at the school, and 32% of household contacts of these ill persons. Of household contacts of persons exposed at school but not clinically ill, 11% developed illness. This value, however, was not statistically different from the level of illness observed concurrently in household contacts of students at an unaffected school nearby. Epidemiologic investigation implicated water as the mode of transmission. Average consumption of one or more glasses per day was strongly associated with illness (p less than 0.00000001). Among soccer team members with limited school contact, water consumption at the school was associated with a 14-fold greater risk of illness (p less than 0.000001). Drinking water was most likely contaminated by back-siphonage through a cross-connection between the school's well and septic tank. This contamination occurred approximately 24 to 36 hours before the outbreak developed.     

Waterborne Gastroenteritis due to the Norwalk Agent: Clinical and Epidemiologic Investigation

An outbreak of gastroenteritis occurred at a Pennsylvania summer camp in July 1978. Symptoms included abdominal pain (81 per cent), nausea (72 per cent), and vomiting (53 per cent); upper respiratory infection symptoms occurred in 35 per cent of the campers. Illness was associated with consumption of five or more glasses of water or water-containing beverages. Stool cultures from affected persons were negative for bacterial pathogens; however, a fourfold or greater rise to the Norwalk agent was demonstrated in serum samples of three of three ill persons tested and in none of eight controls (p < .02). Campers ill during the first session who were also present during the second session did not become ill during the second session (p < .001). (Am J Public Health 1982; 72:72-74.)     

A foodborne outbreak of Norwalk virus gastroenteritis. Evidence for post-recovery transmission

From November 10-16, 1982, 220 (57%) of 383 attendees at eight banquets for which food had been prepared at a single hotel restaurant and the employees of the hotel had onset of Norwalk virus gastroenteritis. Epidemiologic investigation of the three largest banquets confirmed consumption of potato and fruit salads (banquet A), coleslaw (banquet B), and tossed salad (banquet C) to be significantly associated with illness. Between November 8-19, similar illness occurred in seven (54%) of 13 hotel kitchen employees. The foods implicated in banquets A and B were prepared by one salad worker during her acute illness and up to 48 hours following her recovery. A second salad worker prepared the implicated tossed salad for banquet C 24 hours following her recovery. To the authors' knowledge, this is the first foodborne outbreak investigation demonstrating Norwalk viral excretion and transmission by a food handler after recovery from illness and either person-to-person or vehicle-borne transmission between food handlers with subsequent transmission by more than one food handler to patrons.     

Waterborne epidemic outbreak of Shigella sonnei gastroenteritis in Santa Maria de Palautordera, Catalonia, Spain

In August 2002 an outbreak of Shigella sonnei infection occurred in a Spanish town of 6343 inhabitants. In total, 756 people developed acute gastroenteritis and 181 cases were shigella-confirmed. The peak incidence was during 5-6 August 2002. The estimated primary attack rate was 9.97%; the attack rate for secondary cases was 38%. The <15 years ago group was most affected (16.49%). The town and its surroundings were served by two water systems, A and B. The cases had consumed water provided by system A (attack rate 164 cases/1000 population). Microbiological analysis of water from system A did not show the presence of coliform bacteria or shigella. This shigellosis outbreak was the largest reported in Spain. The impact of the epidemic was probably greater than the incidence detected.     

Acute viral gastroenteritis

Two virus-like particles have been found to be associated with acute viral gastroenteritis. One, a 270-nm parvovirus-like particle (the Norwalk agent), was visualized and recognized by immune electron microscopy in an infectious stool filtrate derived from a community outbreak of nonbacterial gastroenteritis. It appears to be one of the etiologic agents of a usually self-limited form of gastroenteritis which commonly occurs in community outbreaks. The other, a 70-nm reovirus-like particle, has been observed by electron microscopy in specimens from infants and children with severe diarrhea in many parts of the world. The reovirus-like particle may emerge as a major etiologic agent of diarrhea of infants and young children.     

Food poisoning outbreak probably of viral etiology caused by Norwalk virus]

In May 1989, a foodborne outbreak of acute gastroenteritis was identified in a state school in Adzaneta, Castellón. A dtudy was undertaken to describe it, investigate its causes, and recommend adequate control measures. Sixteen children and 2 teachers were affected (attack rate: 28.57%). Kaplan and cols clinical and epidemiological criteria for Norwalk-like virus as the responsible agent were present. The probable origin of the outbreak was a foodhandler who was already ill beforehand. The examination of stools of the foodhandler and a patient showed small round structures similar to the Norwalk virus. In Spain, the number of foodborne outbreaks without known causal agent has steadily increased in recent years. It may be that this microorganism is responsible for some of these outbreaks in which, for several reasons, the causal agent cannot be identified.     

南京某小学一起诺如病毒胃肠炎暴发疫情调查

目的分析急性胃肠炎疫情暴发的原因及危险因素。 方法回顾性病例对照研究分析2017年4月26日至 2017年5月5日南京市某小学出现的111例胃肠炎患者。其中男性64例,女性47例;年龄7～36岁,平均年龄(10.84±4.00)岁。通过病例对照研究探索可疑传播因素,选择一、三、五年级病例55例,按1∶1在同班级选择同性别无症状健康人群55例为对照,分析疫情发生的危险因素。采用荧光定量RT-PCR方法对人体、环境及食物标本进行诺如病毒核酸检测。 结果本次疫情共111例病例,其中学生108例(95.7%),教师3例(2.6%)。实验室共检出诺如病毒GⅡ型核酸阳性11份(12.6%),其中9份为学生肛拭子样(56%),1份为学生粪便样(100%),1份为三(1)班门把手涂擦样(3.33%)。病例对照研究结果显示：靠近患者呕吐物1米是危险因素(OR＝3.90,P<0.05),说明直接或间接接触呕吐物或气溶胶是疫情发生的主要危险因素。其他因素暂未发现与该起暴发有统计学意义上的关联。 结论该起感染性腹泻聚集性疫情由诺如病毒引起,密切接触与暴露于患者的呕吐物是最主要的危险因素。