Prolonged outbreak of giardiasis with two modes of transmission

Large outbreaks of giardiasis caused by person-to-person transmission, or a combination of transmission routes, have not previously been reported. A large, prolonged giardiasis outbreak affected families belonging to a country club in a suburb of Boston, Massachusetts, during June-December 2003. We conducted a retrospective cohort study to determine the source of this outbreak. Giardiasis-compatible illness was experienced by 149 (25%) respondents to a questionnaire, and was laboratory confirmed in 97 (65%) of these cases. Of the 30 primary cases, exposure to the children's pool at the country club was significantly associated with illness (risk ratio 3.3, 95% confidence interval 1.7-6.5). In addition, 105 secondary cases probably resulted from person-to-person spread; 14 cases did not report an onset date. This outbreak illustrates the potential for Giardia to spread through multiple modes of transmission, with a common-source outbreak caused by exposure to a contaminated water source resulting in subsequent prolonged propagation through person-to-person transmission in the community. This capacity for a common-source outbreak to continue propagation through secondary person-to-person spread has been reported with Shigella and Cryptosporidium and may also be a feature of other enteric pathogens having low infectious doses.     

Emerging genotype (GGIIb) of norovirus in drinking water, Sweden

From May through June 2001, an outbreak of acute gastroenteritis that affected at least 200 persons occurred in a combined activity camp and conference center in Stockholm County. The source of illness was contaminated drinking water obtained from private wells. The outbreak appears to have started with sewage pipeline problems near the kitchen, which caused overflow of the sewage system and contaminated the environment. While no pathogenic bacteria were found in water or stools specimens, norovirus was detected in 8 of 11 stool specimens and 2 of 3 water samples by polymerase chain reaction. Nucleotide sequencing of amplicons from two patients and two water samples identified an emerging genotype designated GGIIb, which was circulating throughout several European countries during 2000 and 2001. This investigation documents the first waterborne outbreak of viral gastroenteritis in Sweden, where nucleotide sequencing showed a direct link between contaminated water and illness.     

Investigation of an outbreak of acute illness in a school group visiting Sydney, September 2006

OBJECTIVE: We describe the investigation into an outbreak of acute illness in approximately 40 people attending Darling Harbour in Sydney during a school music camp. METHODS: We used three methods, including the Public Health Realtime Emergency Department Surveillance System, to obtain information on the food and travel history of the group and symptoms of the cases rapidly. RESULTS: Forty-five cases of gastroenteritis were identified in people on the bus trip. Most dates of onset of illness were obtained from triage text fields in the NSW Public Health Real Time Emergency Department Surveillance System, and were verified through medical record review and interviews. No causative agent was identified. CONCLUSION: The investigation suggested person-to-person transmission rather than a point source, and demonstrates how the NSW Public Health Real Time Emergency Department Surveillance System can assist with case finding in public health investigations.     

A review of nosocomial norovirus outbreaks: infection control interventions found effective

The purpose of this study was to review documented outbreaks of enteric illness associated with nosocomial norovirus infections and to identify modes of transmission, morbidity and mortality patterns, and recommendations for control. Searches of electronic databases, public health publications, and federal, state/provincial public health websites were completed for 1 January 2000 to 31 December 2010. Computer-aided searches of literature databases and systematic searches of government websites identified 54 relevant outbreak reports. Transmission routes included person-to-person (18.5%), foodborne (3.7%) and in the majority (77.8%) the route was unknown. Actions taken during the outbreak to control infection included restricting the movements of patients and staff (22.5%), enhanced environmental cleaning (13.6%) and hand hygiene (10.3%). Rapid identification of norovirus outbreaks in hospitals is vital for the immediate implementation of infection control measures and isolation of infected individuals in this mainly immunocompromised population. Studies that statistically evaluate infection control measures are needed.     

一起医院内集聚性诺如病毒胃肠炎的调查

目的 调查分析一起在上海市徐汇区某社区卫生服务中心内科病房内发生的集聚性诺如病毒GⅡ型胃肠炎疫情的特征及其原因.方法 采用统一的集体性腹泻个案调查表进行现场流行病学调查,使用病例对照研究方法分析相关危险因素,采用RT-PCR方法检测病毒核酸.结果 该起疫情共报告病例22例,发病率为31.0％,以呕吐腹泻为主要临床表现,疫情流行持续8d,引入率为30.3％;时间分布呈单峰,空间分布有集聚性;通过实验室检测确定有两名护工隐性感染,在11份粪便、肛拭标本中检出9份诺如病毒GⅡ型核酸阳性,6份环节标本呈核酸阴性;由隐性感染护工护理的患者发病率高于非感染护工护理的患者(x2 =4.98,P=0.026),OR值为11.2(95％ CI=1.80～116.80);空间分布的集聚性与隐性感染护工护理的床位高发病率有较好的一致性.结论 该次疫情是一起发生在医疗机构内由诺如病毒GⅡ型引起的集聚性胃肠炎疫情,隐性感染的护工是传染源之一,接触传播是重要的传播途径;该次疫情在对手卫生、标准防护执行力进行干预及落实各项消毒隔离措施后得到有效控制.     

Bayesian model choice and infection route modelling in an outbreak of Norovirus

A data set from an outbreak of gastroenteritis in a school is analysed using a stochastic transmission model. The causative agent of the outbreak is believed to be a Norovirus, spread through person-to-person contact. Particular attention is given to the question of whether or not vomiting episodes enhance the spread of the virus via aerosol transmission. The methodology developed uses Bayesian model choice, implemented with reversible-jump Markov chain Monte Carlo methods. The methodology appears to be highly sensitive to assumptions made concerning the data, which provides some assurance that the conclusions are driven by observations rather than the underlying model and methodology.     

Enteric outbreaks in long-term care facilities and recommendations for prevention: a review

Outbreaks of enteric illness in long-term care facilities (LTCFs) were reviewed to identify preventative recommendations. Systematic review methodology identified outbreak reports of gastrointestinal illness in LTCFs either published or that occurred from January 1997 to June 2007. The inclusion criteria captured 75 outbreaks; 23 (31%) associated with bacterial agents and 52 (69%) with viral agents. Transmission was mainly foodborne (52%) for those of bacterial origin and person-to-person (71%) for viral outbreaks. Norovirus infection was associated with 58% of hospitalizations. Sixty deaths were reported, about half from Salmonella infections. Recommendations for foodborne outbreaks emphasized appropriate sourcing and preparation of eggs, staff training, and temperature control during food preparation. Recommendations from outbreaks transmitted person-to-person centred on controlling residents' movements, effective environmental cleaning and disinfection, cancelling social events and restricting visitors, excluding ill staff, encouraging effective hand hygiene, and preventing cross-contamination through gloving and gowning. In none of the 75 published outbreak reports were the suggested recommendations evaluated for effectiveness in controlling the outbreak. Applied research of this type could greatly help in the acceptance of prevention and control strategies.     

A one-year intensified study of outbreaks of gastroenteritis in The Netherlands

In 2002, in The Netherlands a national study of gastroenteritis outbreaks was performed. Epidemiological information was collected by the Public Health Services (PHS) and the Food Inspection Services (FIS) using standardized questionnaires. Stool samples were collected for diagnostic testing. For foodborne outbreaks, food samples were taken. In total, 281 gastroenteritis outbreaks were included, mainly from nursing homes and homes for the elderly (57%), restaurants (11%), hospitals (9%) and day-care centres (7%). Direct person-to-person spread was the predominant transmission route in all settings (overall 78%), except for restaurant outbreaks where food was suspected in almost 90% (overall in 21% of outbreaks). The most common pathogen was norovirus (54%), followed by Salmonella spp. (4%), rotavirus group A (2%), Campylobacter spp. (1%) and only incidentally others. In conclusion, most outbreaks were reported from health and residential institutions, with norovirus as the dominant agent. Control should aim at reducing person-to-person spread. In foodborne outbreaks norovirus was common, due to contamination of food by food handlers. Salmonella, as the second foodborne pathogen, was mainly associated with raw shell eggs. These results stress the continuous need for food safety education, complementary to governmental regulation.     

Norovirus transmission on cruise ship

An outbreak of norovirus gastroenteritis affected passengers on two consecutive cruises of ship X and continued on 4 subsequent cruises despite a 1-week sanitization. We documented transmission by food and person-to-person contact; persistence of virus despite sanitization onboard, including introductions of new strains; and seeding of an outbreak on land.     

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.     

诺如病毒胃肠炎暴发后环境中病毒检测情况分析

目的 了解诺如病毒胃肠炎暴发后,病例临床症状消失、末例病例发病日期经过最长潜伏期(72 h)且无续发病例的情况下,病例家庭环境及外环境水标本中病毒存在情况.方法 在末例病例发病日期经过最长潜伏期(72h)后,采集病例肛拭标本、家庭环境标本、外环境水标本,采用RT-PCR方法 检测病毒,阳性标本测序分析.结果 9份病例肛拭标本中3份呈阳性;46份家庭环境拭子中2份呈阳性,分别是来自两户已无现症病例的家庭厕所马桶表面;5份外环境水标本中1份呈阳性,即村民粪便直接排入的河涌.病例肛拭、家庭环境拭子及河涌水三者检出的病毒株核苷酸序列一致,提示病毒同源.结论 诺如病毒胃肠炎暴发后期,病例肛拭、病例家庭环境及外环境水标本中仍能检出病毒,因此有必要加强病例的粪便管理及疫情后期的环境消毒,以防粪便污染引起二代病例.     

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。     

A common-source epidemic of mixed bacterial diarrhea with secondary transmission

An epidemic of acute diarrhea in a village in southern India in 1972 was associated with a high rate of isolation of enteric pathogenic bacteria from the patients and lasted for three months. There was no significant association between the prevalence of enteroviruses or parasites and cases of diarrhea. The epidemic started as a common-source outbreak due to the contamination of well water, and there were many secondary cases probably due to a person-to-person spread. The illness did not produce chronic diarrhea or malabsorption.     

Epidemiology and control of an outbreak of typhoid in a psychiatric institution.

An outbreak of typhoid caused by Salmonella typhi of the same Vi-phage type (D1) and of the same antibiogram was reported in a large psychiatric institution in Singapore. A total of 95 (4.8%) of the 1965 inmates were infected, 47 with symptoms and 48 asymptomatic. Transmission was through close person-to-person contact and not through contaminated food or water. The source of infection could not be established. The outbreak was brought under control by maintaining a high standard of environmental sanitation, active search for fever and diarrhoeal cases, identification of asymptomatic cases by rectal swabbing, and isolation of those found to be infected. Mass immunization with two doses of heat-phenol inactivated typhoid vaccine was also carried out concurrently. The vaccine was found to have an efficacy of 65.8% in preventing clinical illness.     

Endemic Norovirus Infections in Children,Ho Chi Minh City,Vietnam, 2009–2010

We performed a case–control investigation to identify risk factors for norovirus infections among children in Vietnam. Of samples from 1,419 children who had diarrhea and 609 who were asymptomatic, 20.6% and 2.8%, respectively, were norovirus positive. Risk factors included residential crowding and symptomatic contacts, indicating person-to-person transmission of norovirus.     

An outbreak of Escherichia coli O157 associated with a children's paddling pool.

In May 1992, a small, circumscribed community outbreak of infection due to verotoxin-producing Escherichia coli O157 phage type 49 occurred in a semi-rural area of south-east Scotland. On the basis of stool cultures, six cases were identified, one of whom was asymptomatic. One child developed the haemolytic uraemic syndrome. Although the source of infection of the index case was not established nor could the extent of person-to-person spread be fully determined, the clinical, microbiological and epidemiological evidence available indicated that a children''s paddling pool served as the focal point in the transmission of infection causing the outbreak.