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PubMed2001

Population dynamics of a scrapie outbreak.

A detailed analysis of a scrapie outbreak in a flock of Cheviot sheep is described. A total of 33 cases of 1473 sheep born to the flock were reported between 1985 and 1994. The epidemiology of scrapie can only be understood with reference to sheep demography, the population genetics of susceptibility to scrapie, pathogenesis during a long incubation period, and the rate of transmission (by both horizontal and vertical routes), all of which interact in complex ways. In recent work a mathematical model incorporating these elements was developed and successfully reproduced key features of an earlier outbreak of scrapie in this flock. Here an application of the model to the second outbreak is described. The model accurately reproduces observed allele frequencies and total numbers of susceptible animals remaining at the end of the outbreak. A major difference between the two outbreaks is the very much lower force of infection in the second outbreak. This provided additional information which suggested two ways in which our existing assumptions be refined; firstly, older animals have reduced susceptibility to scrapie and secondly, homozygous and heterozygous susceptibles have different incubation periods.

Animals↗

PubMed2005

Outbreak of long-term intravascular catheter-related bacteremia due to Achromobacter xylosoxidans subspecies xylosoxidans in a hemodialysis unit.

Achromobacter xylosoxidans is a rare cause of bacteremia. Over a 2-week period, A. xylosoxidans subsp. xylosoxidans was isolated from blood cultures of four hemodialysis patients with long-term intravascular catheters. A culture from one atomizer that contained diluted 2.5% chlorhexidine, which had been used to disinfect the skin, yielded A. xylosoxidans subsp. xylosoxidans. No further cases were diagnosed once the use of this atomizer was discontinued. Five outbreak-related strains from the four patients and the atomizer were tested by pulsed-field gel electrophoresis (PFGE) under XbaI restriction. The isolates from the first three patients and the atomizer had identical PFGE patterns, confirming the atomizer as the source of the outbreak. The strain isolated from the fourth patient had six more bands than the outbreak strain and was considered possibly related to the outbreak strain. All patients were treated with intravenous levofloxacin. The catheter was removed in only one patient. The three patients in whom the catheter was left in place were also treated with antibiotic lock therapy with levofloxacin. All four patients were cured. This is believed to be the first reported outbreak of central venous catheter-related bacteremia due to A. xylosoxidans and the second reported outbreak with this organism associated with chlorhexidine atomizers. The use of diluted chlorhexidine via atomizers can be dangerous for the care of venous catheters and should be called into question. Patients with long-term intravascular catheter-related bacteremia due to this organism can be treated successfully with systemic antimicrobial therapy in addition to antibiotic lock therapy without catheter removal.

Achromobacter denitrificans↗

PubMed2007

Molecular features of astrovirus associated with a gastroenteritis outbreak in an aged-care centre.

The study presented here was conducted in order to gain a better understanding of the role of astroviruses (AsVs) in outbreaks of gastroenteritis among the elderly. This report is the first to provide detailed information on the molecular characteristics of an AsV causing an outbreak in an aged-care centre and is the first to clearly establish that individuals infected in such an outbreak were, in fact, elderly. The outbreak under investigation took place in Victoria, Australia, in October 2005. Twelve individuals (mean age +/- standard deviation [SD] 85.5 +/- 12.3 years) became ill during the outbreak from a total population of 86 susceptible residents. The mean duration (+/-SD) of illness was 2.3 +/- 1.6 days; symptoms included diarrhoea, abdominal pain, nausea and headache. No bacterial pathogens were detected. AsV was identified in five faecal specimens using electron microscopy and reverse transcription-polymerase chain reaction methodologies; no other gastroenteritis virus was detected. Nucleotide sequence analysis indicated the AsV identified could be assigned to the 1d lineage of AsV serotype 1 and that the AsV was not a recombinant form. The findings, taken together with previous work, indicate the AsV serotype most commonly associated with gastroenteritis outbreaks among the elderly is serotype 1 AsV.

Aged, 80 and over↗

PubMed2003

An outbreak of rubella aboard a ship of the German Navy.

BACKGROUND: During May and June 1996, an outbreak of rubella occurred offshore aboard a ship of the German Navy. The outbreak spread among 330 crew members over a period of 9 weeks, ending 2 days after the ship's return. This is the first detailed epidemiological investigation of a rubella outbreak on a ship, describing temporal progression, clinical manifestations, immunization status and seroprevalence of the population exposed. PATIENTS AND METHODS: Outbreak investigation using a questionnaire, health records and rubella serology (hemagglutination inhibition (HI) test and EIA). RESULTS: Of the 330 crew members 298 (90%) participated in the investigation. The outbreak was continuous without a peak and ended abruptly after the ship's return. It resulted in 20 cases, 11 of which were clinically symptomatic. A total of 35 (12%) crew members were susceptible to rubella prior to the outbreak, resulting in an attack rate of 57%. The highest risk for infection was linked to accommodation aboard the ratings deck (chi(2)-test, p = 0.004) with most favorable conditions of transmission. Only 9% of the participating crew were able to provide complete proof of their immunization status. The positive predictive value of a past history of rubella for the presence of antibodies against rubella was 59%. CONCLUSION: The transmission of rubella that we describe aboard a ship was facilitated by the unusually close proximity of the crew and their insufficient immunity. Documentation of immunization was inadequate in this population.

Antibodies, Viral↗

PubMed2004

An outbreak of norovirus gastroenteritis on an Israeli military base.

BACKGROUND: Noroviruses (NVs) are a predominant cause of viral gastroenteritis outbreaks, but they are difficult to identify because they cannot be cultivated in cell culture. Therefore, reverse-transcriptase polymerase chain reaction (RT-PCR) assays are widely used in the testing of clinical stool specimens for NV. However, testing of perianal swabs in the context of an outbreak is considered to be an insensitive method for identification of NV using the RT-PCR technique. An outbreak of acute gastroenteritis involving 159 soldiers on a training base of the Israel Defense Force in December 1999 allowed us to evaluate this identification method. PATIENTS AND METHODS: An epidemiologic investigation, a sanitation survey and a case-control study of exposure to different food items served up to 48 h preceding the outbreak were conducted. Stool samples in the form of post-defecation perianal swabs were collected from 24 ill personnel and three non-ill food handlers. Swabs were tested for the presence of NV by RT-PCR assay. RESULTS: Epidemiologic data were consistent with a pointsource food-borne outbreak which was associated with consumption of fresh vegetable salad in the base mess hall (OR = 4.38, 95% CI 1.51-13.35). Both epidemiologic and clinical features were suggestive of gastroenteritis caused by NV, and upon laboratory analysis perianal swabs from four of 24 cases were positive for NV. CONCLUSION: The combination of practical specimen collection with perianal post-defecation swabs, and the utilization of a molecular epidemiology approach, can simplify the rapid identification of outbreaks caused by NVs.

Adult↗

PubMed1991

Analysis of plasmid pattern in paediatric intensive care unit outbreaks of nosocomial infection due to Enterobacter cloacae.

Sequential outbreaks of nosocomial infection due to multiply-resistant Enterobacter cloacae occurred in September 1987, and between December 1988 and January 1989, in a paediatric intensive care unit. A total of eight neonates were affected and most had received ventilatory support. Initially, we were unable to determine whether the two outbreaks were caused by the same strain of E. cloacae. After applying plasmid profile analysis to identify epidemic strains, we established that the strain from the first outbreak was different from the second outbreak strain, as each had its own plasmid pattern. During the second outbreak, an environmental bacteriological survey was carried out. We found that the distilled water containers were contaminated with E. cloacae which had the same plasmid profile. After changing the distilled water containers and by reinforcement of aseptic techniques, the nosocomial outbreak was terminated.

Cross Infection↗

PubMed1994

A hospital outbreak due to Norwalk virus.

An outbreak of diarrhoea and vomiting began at a hospital for the elderly on the 25 October 1991. The symptoms and pattern of spread suggested a viral aetiology from a point source. Electron microscopy confirmed the presence of Norwalk virus. The first wave of illness affected 37 patients and 28 staff. Secondary cases occurred on all wards. Analytical studies of food consumed at three lunchtime meetings by staff and visitors to the hospital demonstrated a clear association between eating sandwiches and subsequent illness. The source of the outbreak was probably a food handler involved in the preparation of sandwiches. Control measures were implemented and the outbreak was declared over on the 11 November 1991. At this time 95 patients and 69 staff (including six visitors) had been affected. The implications for the future investigation and prevention of outbreaks of viral gastroenteritis in closed communities are discussed. An audit of the action taken during the outbreak resulted in the development of standards for the investigation and control of local outbreaks.

Caliciviridae Infections↗

PubMedDate not supplied

Comparison of arbitrarily primed polymerase chain reaction and cell envelope protein electrophoresis for analysis of Acinetobacter baumannii and A. junii outbreaks.

Two successive Acinetobacter outbreaks in a neonatal intensive care unit were studied with arbitrarily primed polymerase chain reaction (AP-PCR), cell envelope protein electrophoresis (protein fingerprinting) and antibiotic susceptibility testing. AP-PCR fingerprinting and protein fingerprinting yielded identical clustering of the isolates studied. Susceptibility test results were useful for rapid recognition of the outbreaks, but clustering of several isolates was different from the clustering obtained with AP-PCR fingerprinting and protein fingerprinting. Typing results indicated that the two outbreaks, which occurred at a three-month interval, were each caused by a single strain, and that both strains differed from the strains prevailing in the hospital. The strain of one outbreak was identified as A. junii, a species commonly not involved in outbreaks. A. baumannii isolates collected from different departments of this hospital during a period of four years clustered into only five different types. Moreover, strains from different departments of a second hospital belonged to the type prevailing in the first hospital, although there were no apparent connections between the two institutions. This may indicate that only a limited number of strains of the A. calcoaceticus-baumannii complex are involved in nosocomial outbreaks.

Acinetobacter↗

PubMed2005

A National Guard outbreak of Burkholderia cepacia infection and colonization secondary to intrinsic contamination of albuterol nebulization solution.

BACKGROUND: Burkholderia cepacia, a gram-negative pathogen, has been a known cause of hospital outbreaks because of a contaminated common source such as multidose medications. We describe an outbreak with Burkholderia cepacia infection in 2 major hospitals affiliated to the National Guard, related to an intrinsic contamination of a locally manufactured, multidose Albuterol nebulization solution (Tabouk Pharmaceutical Company, Tabouk, Saudi Arabia) and we report the interventions taken to interrupt this outbreak. METHODS: During the outbreak period between May 2003 and March 2004, a combined prospective surveillance and a retrospective chart and microbiologic data review were conducted in 4 major hospitals affiliated to the National Guard. Microbiologic cultures were also performed on environmental objects of concern, as well as certain medications. In addition, a questionnaire was distributed to the respiratory therapy staff to evaluate the process of administering respiratory medications and their adherence to sound infection control practices. RESULTS: An intrinsic contamination of a locally manufactured brand of multidose Albuterol nebulization with B cepacia was identified. Two of the 4 hospitals were found to be involved: hospital A a 700-bed tertiary care center and Hospital B a 150-bed hospital. A total of 2121 patients were exposed to Albuterol nebulization as inpatients at hospital A and 318 as outpatients. For hospital B, a total of 283 inpatients and 34 outpatients were exposed to the Albuterol nebulization. Forty and 12 patients, from hospital A and hospital B, respectively, were found to have at least 1 positive culture for B cepacia. From hospital A, most samples were respiratory, and, from hospital B, most were from blood. Molecular typing of 34 available isolates showed that 23 cases were of a single strain of B cepacia that matched the strain isolated from the 3 different batches of multidose Albuterol nebulization. Three culture-positive patients never received Albuterol nebulization of that brand but were in the same room of a patient who had been receiving the medication. CONCLUSIONS: We identified a large outbreak of B cepacia in 2 major hospitals affiliated with the National Guard, linked to an intrinsic contamination of a multidose Albuterol nebulization solution. During the period of prospective surveillance, only a few cases were identified as a result of nosocomial transmission. Immediate notification of the Ministry of Health and withdrawal of the medication and revisiting the respiratory therapy practices were necessary to halt this outbreak.

Adolescent↗

PubMed2006

An outbreak of noninvasive group A streptococcal disease in a facility for the developmentally disabled.

BACKGROUND: Reports of outbreaks of group A streptococcal disease in long-term care facilities are uncommon. METHODS: An outbreak of noninvasive group A streptococcal disease was investigated in a large facility for the developmentally disabled. The antistreptolysin O test was used to supplement the case finding. RESULTS: Sixty-seven cases of streptococcal pharyngitis were diagnosed among residents and staff of the facility. Interventions based on enhanced infection control practices were effective, but maintaining them for several months was challenging because of the large number of staff, cognitive deficits of the residents, inconveniently placed areas for hand sanitation for the staff, and occurrence of a simultaneous outbreak of impetigo in the same population. After 4 months, the outbreak was successfully managed without chemoprophylaxis of the entire residential population and staff. CONCLUSION: Outbreaks of group A streptococcal disease in centers for persons with developmental disabilities have unique challenges superimposed on routine outbreak response measures.

Anti-Bacterial Agents↗

PubMed2005

Use of a systems-based approach to an environmental health assessment for a waterborne disease outbreak investigation at a snowmobile lodge in Wyoming.

Investigations into disease outbreaks generally incorporate an epidemiologic investigation, laboratory analysis, and an environmental health assessment. This last component is designed to discover connections between factors in the environment and the outbreak, but is often limited, either by time and resources, or the expertise of the personnel included in outbreak investigation teams. A waterborne Norovirus outbreak investigation in Sheridan County, Wyoming, in 2001 provides an excellent example of the importance of including an in-depth, systems-based environmental health assessment in outbreak investigations. The epidemiologic component of this investigation identified the water supply of a snowmobile lodge in the Bighorn Mountains as the source of the outbreak, a result that was confirmed by laboratory analysis. Including a systems-based environmental health assessment in this investigation also helped to uncover the underlying environmental factors that led to contamination of the water supply. Those factors included an onsite wastewater disposal system that was overloaded by increased use and not well suited to local soil and geologic conditions and a drinking water system with no treatment or disinfection. In addition, heavy precipitation and increased pumping of wells to satisfy higher demands probably facilitated the contamination of the drinking water wells by causing greater movement of wastewater through the soil and underlying bedrock. By focusing on these links between factors in the environment and adverse health outcomes, the systems-based environmental health assessment also helped to highlight prevention strategies for avoiding recurrences.

Caliciviridae Infections↗

PubMed2006

The influence of staff and resident immunization rates on influenza-like illness outbreaks in nursing homes.

OBJECTIVE: To evaluate the influence of immunization rates on the likelihood of influenza-like illness (ILI) clusters in nursing facilities. DESIGN: Retrospective cross-sectional study. SETTING: Nursing facilities in a single for-profit chain (N = 301). PARTICIPANTS: Nursing home residents and staff in each facility. MEASUREMENTS: Resident and staff influenza immunization rates during the 2004-2005 influenza season, indicator of ILI cluster in facility defined as 3+ ILI cases reported within 72 hours in close proximity within the facility, hospitalization and mortality rates for facilities reporting ILI clusters, indicator of confirmatory laboratory testing for ILI cases in facility. RESULTS: Staff (median = 38%) and resident (median = 85%) rates of immunization did not independently predict the likelihood of an outbreak but jointly were strong predictors. For example, facilities having greater than 55% of staff and greater than 89% of residents immunized were almost 60% less likely to have an ILI cluster (odds ratio [OR]: 0.410; 95% CI: 0.19, 0.89) compared to all others. Facilities with higher proportions of Medicaid-funded residents were less likely to have an outbreak. Each 1% increase in the proportion of residents with Medicaid was associated with a 2.5% decrease in the risk of a cluster (OR: 0.975; 95% CI: 0.956, 0.995). Bed size and staff size did not significantly influence the likelihood of an outbreak. Among facilities with outbreaks, higher vaccination rates did not predict lower rates of hospitalizations or deaths. Approximately two thirds of all ILI clusters had laboratory testing to confirm the diagnosis of influenza. Three quarters of the facilities in which outbreaks occurred and for which confirmatory tests were performed (50/67, 74.6%) had 1+ cases positively identified as influenza. CONCLUSION: Both staff and residents must have high rates of vaccination to substantially alter the rate and impact of influenza outbreaks in nursing facilities.

Aged↗

PubMed2005

An outbreak of primary dengue infection among migrant Chinese workers in Singapore characterized by prominent gastrointestinal symptoms and a high proportion of symptomatic cases.

BACKGROUND: An outbreak of dengue occurred among Chinese migrant workers at a construction site in Singapore that was characterized by a number of unusual features. METHODS: Clinical and laboratory data were prospectively collected from workers who were hospitalized with fever. We compared the frequency of disease manifestations in these patients with historical data from other cases of dengue admitted to the same centre. A serological survey was performed at the construction site one month after the onset of the outbreak. RESULTS: Thirty-nine patients were admitted from the affected construction site with confirmed acute dengue infection in March and April 2002. Fever, headache and rash were common and occurred at similar frequency in outbreak patients and historical controls. Gastrointestinal manifestations were significantly more common in the outbreak patients compared with controls (nausea 68%, diarrhea 41%, hyponatremia 47% and elevated urea 20%). Of the 274 studied in the serological survey, 27 had serological evidence of acute dengue, of whom 24 (89%) had experienced a febrile illness in the previous month. The virus was cultured and identified as Dengue-2. Few patients had a positive IgG for dengue indicating that this was likely a primary infection. CONCLUSION: This outbreak of primary dengue infection was characterized by unusually prominent gastrointestinal symptoms and a high proportion of symptomatic transmission. Manifestations of dengue may be altered when outbreaks involve immunologically naïve adults who have migrated to dengue endemic areas.

Adult↗

PubMed2005

Institutional risk factors for outbreaks of nosocomial gastroenteritis: survival analysis of a cohort of hospital units in South-west England, 2002-2003.

Nosocomial outbreaks of gastroenteritis are a major burden on hospital inpatient services, costing an estimated pound115 million annually to the English National Health Service. We actively followed-up 171 inpatient units from four major acute hospitals and 11 community hospitals in South-west England for one year. Outbreaks of gastroenteritis were ascertained through an active surveillance network using standard clinical definitions. Survival analysis Cox regression models using an outbreak of gastroenteritis as the endpoint were fitted to identify institutional and operational attributes related to increased outbreak rates at the level of the care unit. Greater number of beds in unit [hazard ratio (HR) 1.22 (per 10 additional beds), 95% confidence intervals (CI) 0.96-1.55] was associated with increased hazard, as were geriatric (HR 2.6, 95%CI 1.6-4.3) and general medical (HR 1.7, 95%CI 1.1-2.6) care units. The average length of stay on a unit was inversely associated with outbreak incidence [HR=0.89 (per additional week of stay), 95%CI 0.80-0.99]. Larger care units and those with higher throughput have increased rates of gastroenteritis outbreaks. These results should guide infection control policy and support the design of hospitals with smaller care units.

Caliciviridae Infections↗

PubMed2005

Outbreaks of contaminated broncho-alveolar lavage related to intrinsically defective bronchoscopes.

From 5 March 2001 to 19 October 2001, outbreaks of broncho-alveolar lavage (BAL) contamination with Enterobacteraceae were detected in our 700-bed institution. We report the investigation of these outbreaks. A case was defined as the occurrence of pairs of specific Enterobacteraceae in BAL specimens among any patients who underwent bronchoscopy in the respiratory unit during the period of the outbreak. Contamination was identified in 117 BAL samples during three outbreaks among 418 patients, and was associated with bronchoscopes 11 and 12 (P<0.001). The other five devices in use were not linked with the outbreaks. During the first outbreak, particular pairs of micro-organisms were associated with a specific bronchoscope (Klebsiella pneumoniae/Proteus vulgaris with bronchoscope 11, and Morganella morganii/Proteus mirabilis with bronchoscope 12). Cultures of sputa from two patients also yielded M. morganii some days after bronchoscopic examination. Isolates from contaminated BAL samples and bronchoscope 11 had similar patterns by pulsed-field gel electrophoresis. No further cases occurred after removal of the implicated bronchoscopes. No deficiencies in disinfection procedures were detected and the source of contamination was found to be a loose port of the biopsy channel of the bronchoscope. Our findings underscore the urgent need to test bronchoscopic samples regularly and to improve the design and structure of bronchoscopes.

Bronchoalveolar Lavage Fluid↗

PubMed2005

An outbreak of Pantoea spp. in a neonatal intensive care unit secondary to contaminated parenteral nutrition.

Contaminated parenteral nutrition (PN) is an important source of infection in neonates. Many organisms have been reported to cause contamination that results in outbreaks in intensive care units. The objective of this study was to investigate an outbreak caused by Pantoea spp., which contaminates PN, in a neonatal intensive care unit (NICU). This was a descriptive study of an outbreak of sepsis in an NICU of a tertiary teaching hospital in Malaysia. Pantoea spp. infection was detected in eight patients over a three-day period from 24 to 27 January 2004 following the administration of PN. Seven of the eight patients died due to the infection. Extensive environmental samplings for culture were performed. PN solution from the NICU and the pharmacy were also cultured during the outbreak period. Pantoea spp. was isolated from blood cultures of all infected patients, and the unused PN from the pharmacy and the NICU. All the strains of Pantoea spp. had a similar antibiotic susceptibility pattern and biochemical reaction. From the results, we concluded that PN was the source of the outbreak and the contamination may have occurred during its preparation in the pharmacy. A thorough investigation has been carried out and, where possible, corrective measures have been taken to avoid similar outbreaks in the future.

Bacterial Typing Techniques↗

PubMed2005

Outbreak of adenovirus type 30 in a neonatal intensive care unit.

OBJECTIVES: To describe an outbreak of adenovirus, type 30, in a neonatal intensive care unit (NICU). STUDY DESIGN: This was a retrospective, observational study. RESULTS: An outbreak of adenovirus infection occurred in an NICU. It lasted 6 months and involved 21 of 333 (6.3%) infants. The introduction of infection control measures controlled the outbreak; however, premature discontinuation of the measures resulted in a second wave of cases. The virus caused pneumonia in 7 infants, conjunctivitis in 7 infants, pneumonia and conjunctivitis in 1 infant, and upper respiratory tract illness in 1 infant. Infection was asymptomatic in 5 infants. Six infants died. Death was associated with the presence of pneumonia ( P = .0001), administration of steroids ( P = .003), and mechanical ventilation ( P = .02). Investigation into the origin of the outbreak suggested that the virus may have been introduced and spread during ophthalmologic procedures. CONCLUSIONS: Adenovirus type 30 can cause severe disease among premature infants in an NICU. Infants with severe bronchopulmonary dysplasia requiring mechanical ventilation are more likely to have development of adenovirus pneumonia and die. Standard infection control measures are effective in controlling an outbreak. Ophthalmologic procedures continue to be a potential source of adenovirus outbreaks.

Adenoviridae Infections↗

PubMed2006

Impact of quarantine on the 2003 SARS outbreak: a retrospective modeling study.

During the 2003 Severe Acute Respiratory Syndrome (SARS) outbreak, traditional intervention measures such as quarantine and border control were found to be useful in containing the outbreak. We used laboratory verified SARS case data and the detailed quarantine data in Taiwan, where over 150,000 people were quarantined during the 2003 outbreak, to formulate a mathematical model which incorporates Level A quarantine (of potentially exposed contacts of suspected SARS patients) and Level B quarantine (of travelers arriving at borders from SARS affected areas) implemented in Taiwan during the outbreak. We obtain the average case fatality ratio and the daily quarantine rate for the Taiwan outbreak. Model simulations is utilized to show that Level A quarantine prevented approximately 461 additional SARS cases and 62 additional deaths, while the effect of Level B quarantine was comparatively minor, yielding only around 5% reduction of cases and deaths. The combined impact of the two levels of quarantine had reduced the case number and deaths by almost a half. The results demonstrate how modeling can be useful in qualitative evaluation of the impact of traditional intervention measures for newly emerging infectious diseases outbreak when there is inadequate information on the characteristics and clinical features of the new disease-measures which could become particularly important with the looming threat of global flu pandemic possibly caused by a novel mutating flu strain, including that of avian variety.

Communicable Diseases, Emerging↗