A community hospital outbreak of legionellosis. Transmission by potable hot water

Seven cases of nosocomial legionellosis occurred between February and September 1982 in a small community hospital in Upstate New York. All seven were cases of Legionella pneumophila serogroup 1; six were hospital patients and one a hospital employee. None of the cases died. During the peak of the outbreak, the incidence of nosocomial legionellosis was 1.2 cases per 100 patient discharges. An epidemiologic comparison of the six patient cases with 21 matched patient controls suggested that longer hospital stay (chi 1(2) = 24.2, p less than 0.001) and the proximity of patients' rooms to ward showers (chi 1(2) = 4.4, p less than 0.04) were significant risk factors for acquiring legionellosis. An environmental investigation demonstrated that the ward showers and the hospital hot water system were contaminated with L. pneumophila serogroup 1. Monoclonal antibody subtyping performed on isolates obtained during the outbreak investigation confirmed that the hot water system and patient isolates had an identical pattern of reactivity. The outbreak demonstrates that legionellosis can be a significant cause of nosocomial pneumonia in a community hospital and that transmission can occur from contaminated potable hot water sources, potentially via shower aerosols.     

Outbreak of Legionnaires' disease at University Hospital, Nottingham. Epidemiology, microbiology and control.

Twelve patients in a large teaching hospital contracted Legionnaires'' disease over a period of 11 months. The source was a domestic hot water system in one of the hospital blocks, which was run at a temperature of 43 degrees C. Five different subtypes of Legionella pneumophila serogroup 1 have been isolated from water in different parts of the hospital, over a period of time. Only one subtype, Benidorm RFLP 14, was implicated in disease. Circumstantial evidence suggested that the outbreak may have been due to recent colonization of the hot water system with a virulent strain of Legionella pneumophila. The outbreak was controlled by raising the hot water temperature to 60 degrees C, but careful surveillance uncovered two further cases in the following 30 months. Persistent low numbers of Legionella pneumophila were isolated from the domestic hot water of wards where Legionnaires'' disease had been contracted, until an electrolytic unit was installed releasing silver and copper ions into this supply.     

Prevention and control of Legionella infection in the hospital environment

An outbreak of nosocomial legionnaires' disease in a hospital of Northern Italy is described, together with the epidemiological survey and the control measures adopted. Two patients developed Legionella pneumophila (serogroup 1) pneumonia, one (immunodepressed) died. The Task Group organised by the Health Service excluded other previous nosocomial infections, and made controls on patients and personnel of at risk units (all negative). An intensive programme of environmental sampling and educational activities on personnel have been carried out. The environmental surveillance revealed that the centralised hot water distribution system of the hospital was colonised with Legionella. Shock heating and hyperchlorination of water were applied, which reduced the number of contaminated sites short term, but recolonisation took place two months later. We underline the difficulties encountered to control Legionella by active surveillance of water quality; once the system is contamined, Legionella eradication may be difficult and expensive, and cases of hospital-acquired legionnaieres' disease are likely to occur.     

Control of nosocomial Legionnaires' disease by keeping the circulating hot water temperature above 55 degrees C: experience from a 10-year surveillance programme in a district general hospital

After a nosocomial outbreak of Legionnaires' disease in a 450-bed district general hospital in 1991, the circulating hot water temperature was kept above 55 degrees C as the sole control measure. From 1991 to 2000, all cases of nosocomial pneumonia were clinically monitored and tested for Legionella pneumophila serogroup 1 by serology or urinary antigen detection. Water samples from peripheral tap sites were cultured for Legionella spp. twice a year. An infection with L. pneumophila serogroup 1 was diagnosed in four out of 366 (1.1%) patients treated for nosocomial pneumonia, representing one case per 26,000 admissions. All patients were cured without complications. L. pneumophila serogroup 1 was isolated in 30 of 251 (12%) cultured hospital water samples during the monitoring period. We conclude that control of nosocomial Legionnaires' disease in a primary referral hospital is possible by keeping the circulating hospital hot water temperature above 55 degrees C, together with careful clinical surveillance. Complete eradication of Legionella spp. from the hot water system does not seem necessary.     

Legionella pneumophila in a hospital water system following a nosocomial outbreak: prevalence, monoclonal antibody subgrouping and effect of control measures

Swabs and water samples from a hospital water system were cultured for legionellae over an extended period. Legionella pneumophila serogroup 1, including outbreak associated strains, were isolated in small numbers from approximately 5% of these samples despite implementation of the current DHSS/Welsh Office regulations. No cases of nosocomial legionnaires' disease were proven during the study. Physical cleaning and chemical sterilization of taps, and replacement of washers with 'approved' brands did not eradicate the organisms. Eradication of legionellae in hospital water supplies appears to be unnecessary in preventing nosocomial legionnaires' disease provided the current DHSS/Welsh Office recommendations are implemented.     

The Stafford outbreak of Legionnaires' disease

A large outbreak of Legionnaires' disease was associated with Stafford District General Hospital. A total of 68 confirmed cases was treated in hospital and 22 of these patients died. A further 35 patients, 14 of whom were treated at home, were suspected cases of Legionnaires' disease. All these patients had visited the hospital during April 1985. Epidemiological investigations demonstrated that there had been a high risk of acquiring the disease in the out patient department (OPD), but no risk in other parts of the hospital. The epidemic strain of Legionella pneumophila, serogroup 1, subgroup Pontiac 1a was isolated from the cooling water system of one of the air conditioning plants. This plant served several departments of the hospital including the OPD. The water in the cooling tower and a chiller unit which cooled the air entering the OPD were contaminated with legionellae. Bacteriological and engineering investigations showed how the chiller unit could have been contaminated and how an aerosol containing legionellae could have been generated in the U-trap below the chiller unit. These results, together with the epidemiological evidence, suggest that the chiller unit was most likely to have been the major source of the outbreak. Nearly one third of hospital staff had legionella antibodies. These staff were likely to have worked in areas of the hospital ventilated by the contaminated air conditioning plant, but not necessarily the OPD. There was evidence that a small proportion of these staff had a mild legionellosis and that these 'influenza-like' illnesses had been spread over a 5-month period. A possible explanation of this finding is that small amounts of aerosol from cooling tower sources could have entered the air-intake and been distributed throughout the areas of the hospital served by this ventilation system. Legionellae, subsequently found to be of the epidemic strain, had been found in the cooling tower pond in November 1984 and thus it is possible that staff were exposed to low doses of contaminated aerosol over several months. Control measures are described, but it was later apparent that the outbreak had ended before these interventions were introduced. The investigations revealed faults in the design of the ventilation system.     

全球铜绿假单胞菌医院感染暴发事件的流行特征与应对策略

目的 了解铜绿假单胞菌引起的医院感染暴发事件,为针对性预防与控制暴发提供参考。方法 计算机检索2005年1月1日—2022年7月18日全球医院感染暴发数据库、PubMed数据库铜绿假单胞菌医院感染暴发事件,阅读全文将调查内容录入Excel表,对相关数据汇总分析,采用Meta分析方法从病例对照与队列研究中提取铜绿假单胞菌获得与传播的危险因素进行系统评价。结果 2005年1月1日—2022年7月18日,27个国家发生149起铜绿假单胞菌医院感染暴发,78起明确了暴发源,主要涉及医院水系统(35.90%)与医疗设备(43.59%);铜绿假单胞菌的传播主要通过受污染的医疗设备(34.82%)和水系统(32.14%),其次通过接触污染的手(16.96%)和环境物体表面(16.07%);通过对不同暴发源采取针对性措施以及强化实施基础性措施,79.8%的铜绿假单胞菌医院感染暴发终止;脉冲凝胶电泳(86次)、聚合酶链式反应(21次)和全基因组测序(8次)是暴发调查中最广泛使用的分子分型方法;纳入的15篇病例对照研究Meta分析结果显示,住院时间(OR=30.87,95%CI:11.89～80.16)、...     

Fault tree analysis of the causes of waterborne outbreaks

Prevention and containment of outbreaks requires examination of the contribution and interrelation of outbreak causative events. An outbreak fault tree was developed and applied to 61 enteric outbreaks related to public drinking water supplies in the EU. A mean of 3.25 causative events per outbreak were identified; each event was assigned a score based on percentage contribution per outbreak. Source and treatment system causative events often occurred concurrently (in 34 outbreaks). Distribution system causative events occurred less frequently (19 outbreaks) but were often solitary events contributing heavily towards the outbreak (a mean % score of 87.42). Livestock and rainfall in the catchment with no/inadequate filtration of water sources contributed concurrently to 11 of 31 Cryptosporidium outbreaks. Of the 23 protozoan outbreaks experiencing at least one treatment causative event, 90% of these events were filtration deficiencies; by contrast, for bacterial, viral, gastroenteritis and mixed pathogen outbreaks, 75% of treatment events were disinfection deficiencies. Roughly equal numbers of groundwater and surface water outbreaks experienced at least one treatment causative event (18 and 17 outbreaks, respectively). Retrospective analysis of multiple outbreaks of enteric disease can be used to inform outbreak investigations, facilitate corrective measures, and further develop multi-barrier approaches.     

An outbreak of waterborne cryptosporidiosis in Swindon and Oxfordshire.

An outbreak of cryptosporidiosis resulted in 516 cases in Wiltshire and Oxfordshire. The outbreak caused widespread interest and led to an official inquiry. The majority of cases were in children; 8% of cases were admitted to hospital and the median duration of illness was 3 weeks. The geographical distribution of cases matched the distribution of water supplies from three treatment works and cryptosporidium oocysts were found at these works and in the treated water. Attack rates in electoral wards supplied by the three treatment works were significantly higher than in other wards. The cause of the outbreak appeared to be the failure of normal treatment to remove oocysts. Measures at the treatment works reduced the number of oocysts detected in treated water, after which the outbreak came to an end. The conclusion of the investigations was that cryptosporidiosis is a risk of conventionally treated public water supplies.     

Fatal nosocomial Legionnaires' disease: relevance of contamination of hospital water supply by temperature-dependent buoyancy-driven flow from spur pipes.

The investigation, epidemiology, and effectiveness of control procedures during an outbreak of Legionnaires'' disease involving three immunosuppressed patients are described. The source of infection appeared to be a network of fire hydrant spurs connected directly to the incoming hospital mains water supply. Removal of these hydrants considerably reduced, but failed to eliminate, contamination of water storage facilities. As an emergency control procedure the incoming mains water was chlorinated continuously. Additional modifications to improve temperature regulation and reduce stagnation also failed to eliminate the legionellae. A perspex test-rig was constructed to model the pre-existing hospital water supply and storage system. This showed that through the hydraulic mechanism known as ''temperature buoyancy'', contaminated water could be efficiently and quickly exchanged between a stagnant spur pipe and its mains supply. Contamination of hospital storage tanks from such sources has not previously been considered a risk factor for Legionnaires'' disease. We recommend that hospital water storage tanks are supplied by a dedicated mains pipe without spurs.     

Surveillance of hospital water and primary prevention of nosocomial legionellosis: what is the evidence?

Hospital-acquired Legionnaires' disease may be sporadic or may occur as part of an outbreak. As Legionella spp. are ubiquitous in many water systems, it is not surprising that hospital water may be colonized with Legionella pneumophila and other species. However, there is some controversy about the relationship between the presence of legionella in hospital water systems and nosocomial legionellosis. Primary prevention, i.e. measures to prevent legionella in a hospital or healthcare facility with no previous documented cases of nosocomial legionellosis, includes heightened awareness of hospital-acquired Legionnaires' disease with appropriate laboratory diagnostic facilities, and ensuring that the water system is well designed and maintained in accordance with national standards, e.g. the circulating hot water is maintained above 55 degrees C. Secondary prevention, i.e. preventing further cases occurring when a case has been confirmed, should include an investigation to exclude the hospital water system as a source. However, the necessity to sample hospital water routinely to detect legionella outside of outbreaks, i.e. as a component of primary prevention, is unclear. Some studies demonstrate a clear link but others do not. Differences between the patient populations studied, the methods of laboratory diagnosis of clinical cases, the analysis of hospital water and differences in the design of hospital water systems may partly explain this. Whilst further research, probably in the form of multi-centred prospective trials, is needed to confirm the relationship between environmental legionella and hospital-acquired legionellosis, including establishing the relative importance of L. pneumophila group 1 vs. non-group 1 and other Legionella spp., each hospital should consider the spectrum of patients at particular risk locally. Centres with transplant units or other patients with significant immunosuppression should, in the interim, consider routine sampling for legionella in hospital water in addition to other control measures. Therefore, infection control teams must work closely with hospital engineering and technical services departments and hospital management, as well as ensuring that physicians and others have a heightened awareness of hospital-acquired legionellosis.     

An outbreak of Norwalk-like gastroenteritis associated with contaminated drinking water at a caravan park

Abstract: During the 1989 Christmas holiday period, a large outbreak of gastroenteritis occurred among persons staying at a caravan park in southern New South Wales. Review of local hospital records found that 77 per cent of patients presenting with infective diarrhoea between 29 December and 3 January had stayed at the caravan park. In a retrospective cohort study we compared rates of illness among caravan park patrons exposed to different water sources. Stools were tested for pathogens and convalescent sera for viral antibodies. Rain and reticulated river water sampled from the caravan park were tested for bacteria and viruses. Of 351 persons interviewed at the caravan park, 305 (87 per cent) reported an illness characterised by diarrhoea, vomiting and abdominal pain. Of 196 persons who used reticulated river water for drinking or ablutions, 175 (89 per cent) became ill compared with 47 of 72 persons (65 per cent) who did not use this water (relative risk 1.4, 95 per cent confidence interval 1.2 to 1.6). The outbreak was probably caused by a 27–28 nm small round structured virus found in the stool from one ill person. High levels of faecal coliforms in the reticulated river water and enterovirus in sediment samples suggest that the outbreak was caused by sewage contaminating the reticulated river water through a break in the pipe directly over the underground water tanks. To prevent such outbreaks, poor water and sewerage system layouts should be avoided and nonpotable water should be clearly labelled. Where feasible, all camping-ground water should stem from town supplies.     

胞曼不动杆菌致下呼吸道感染暴发的调查及干预

目的探讨胞曼不动杆菌致下呼吸道感染暴发的危险因子，为临床干预及控制提供依据。方法按照卫生部医院感染诊断标准对14位胞曼不动杆菌感染患者进行回顾性病史分析。结果14例病例中70岁以上患者占79％，57％的患者具有一种以上潜在性疾病，平均住院日延长了7倍，78％的患者感染前有长期二联以上抗生素使用史，100％患者在感染前接受侵入性治疗。在医护人员手、呼吸机积水器、口腔护理用水、气管切开面罩、床头柜上检测出本次感染暴发的细菌。结论接触传播是此次感染暴发的传播途径。加强医护人员手部卫生和无菌操作，重视环境、设备表面消毒，建立预警机制可降低或控制感染暴发的发生。     

Recurrent Sphingomonas paucimobilis -bacteraemia associated with a multi-bacterial water-borne epidemic among neutropenic patients

A cluster of septicaemias due to several water-related species occurred in a haematological unit of a university hospital. In recurrent septicaemias of a leukaemic patient caused by Sphingomonas paucimobilis, genotyping of the blood isolates by use of random amplified polymorphic DNA-analysis verified the presence of two distinct S. paucimobilis strains during two of the separate episodes. A strain of S. paucimobilis identical to one of the patient's was isolated from tap water collected in the haematological unit. Thus S. paucimobilis present in blood cultures was directly linked to bacterial colonization of the hospital water system. Heterogeneous finger-printing patterns among the clinical and environmental isolates indicated the distribution of a variety of S. paucimobilis clones in the hospital environment. This link also explained the multi-microbial nature of the outbreak.     

An outbreak of xylene intoxication in a hospital

On January 3, 1980 an outbreak of illness occurred in 15 employees of a small community hospital. Symptoms included headache, nausea, vomiting, and dizziness or vertigo; the duration of illness ranged from 2 to 48 hours. The employees who became ill all worked in areas of the hospital served by one central ventilation system. None of the 180 persons working in other parts of the hospital developed symptoms requiring medical care. Less than 1 hour before the outbreak occurred, 1 liter of liquid xylene had been discarded down a sink drain in the pathology laboratory. Simulation experiments confirmed that xylene vapor could have been drawn into the room that contained the fan unit of the ventilation system. This outbreak illustrates an unusual route of exposure to a widely used laboratory chemical.     

An outbreak of multidrug-resistant Pseudomonas aeruginosa associated with increased risk of patient death in an intensive care unit.

OBJECTIVE: To investigate an outbreak of multidrug-resistant Pseudomonas aeruginosa in an intensive care unit (ICU). DESIGN: Epidemiologic investigation, environmental assessment, and ambidirectional cohort study. SETTING: A secondary-care university hospital with a 10-bed ICU. PATIENTS: All patients admitted to the ICU receiving ventilator treatment from December 1, 1999, to September 1, 2000. RESULTS: An outbreak in an ICU with multidrug-resistant isolates of P aeruginosa belonging to one amplified fragment-length polymorphism (AFLP)-defined genetic cluster was identified, characterized, and cleared. Molecular typing of bacterial isolates with AFLP made it possible to identify the outbreak and make rational decisions during the outbreak period. The outbreak included 19 patients during the study period. Infection with bacterial isolates belonging to the AFLP cluster was associated with reduced survival (odds ratio, 5.26; 95% confidence interval, 1.14 to 24.26). Enhanced barrier and hygiene precautions, cohorting of patients, and altered antibiotic policy were not sufficient to eliminate the outbreak. At the end of the study period (in July), there was a change in the outbreak pattern from long (December to June) to short (July) incubation times before colonization and from primarily tracheal colonization (December to June) to primarily gastric or enteral July) colonization. In this period, the bacterium was also isolated from water taps. CONCLUSION: Complete elimination of the outbreak was achieved after weekly pasteurization of the water taps of the ICU and use of sterile water as a solvent in the gastric tubes.     

Clinical and Economic Outcomes of Genome Sequencing Availability on Containing a Hospital Outbreak of Resistant Escherichia coli in Australia

ObjectivesTo evaluate the outbreak size and hospital cost effects of bacterial whole-genome sequencing availability in managing a large-scale hospital outbreak.MethodsWe built a hybrid discrete event/agent-based simulation model to replicate a serious bacterial outbreak of resistant Escherichia coli in a large metropolitan public hospital during 2017. We tested the 3 strategies of using whole-genome sequencing early, late (actual outbreak), or not using it and assessed their associated outbreak size and hospital cost. The model included ward dynamics, pathogen transmission, and associated hospital costs during a 5-month outbreak. Model parameters were determined using data from the Queensland Hospital Admitted Patient Data Collection (N = 4809 patient admissions) and local clinical knowledge. Sensitivity analyses were performed to address model and parameter uncertainty.ResultsAn estimated 197 patients were colonized during the outbreak, with 75 patients detected. The total outbreak cost was A$460 137 (US$317 117), with 6.1% spent on sequencing. Without sequencing, the outbreak was estimated to result in 352 colonized patients, costing A$766 921 (US$528 547). With earlier detection from use of routine sequencing, the estimated outbreak size was 3 patients and cost A$65 374 (US$45 054).ConclusionsUsing whole-genome sequencing in hospital outbreak management was associated with smaller outbreaks and cost savings, with sequencing costs as a small fraction of total hospital costs, supporting the further investigation of the use of routine whole-genome sequencing in hospitals.     

Investigation of an outbreak of central venous catheter-associated bloodstream infection due to contaminated water.

An outbreak of central venous catheter-associated bloodstream infections was reported in a hospital in Ecuador. Commercially produced ampoules of water for injection were found to be contaminated with Burkholderia cepacia and Myroides odoratus. Removal of these ampoules yielded a 10-fold reduction in the incidence of catheter-associated infection.     

新型冠状病毒肺炎疫情期间孕产妇感染防控模式探索

孕产妇是新型冠状病毒易感人群,一旦感染,病情发展迅速,易进展为重症,因此,应高度重视孕产妇新型冠状病毒肺炎防控,避免孕产妇院内感染暴发。结合医院实际,从新型冠状病毒肺炎疫情期间孕产妇分级防控体系、分区分类管理、接诊处理、信息报送、日常督查及出院远程随访等内容进行探讨,旨在探索综合医院新型冠状病毒肺炎疫情期间孕产妇感染防控管理模式。