SEARCH · PubMed Health

Results for “outbreak”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19Linked to original sources

PubMed1992

Nosocomial diarrhoea due to a single strain of Clostridium difficile: a prolonged outbreak in elderly patients.

An outbreak of diarrhoea occurred in an acute geriatric ward of a hospital (A). It affected six patients initially and was found to be due to a single strain of Clostridium difficile. There was little evidence for asymptomatic carriage of this strain or others in the hospital patients. The following three months saw an increase in the number of symptomatic cases of C. difficile disease in two peripheral hospitals, B and C. Patients had been moved from the outbreak ward to these hospitals. Of 18 cases in hospital B all 15 isolates saved for typing were of the 'outbreak' strain. Of three cases occurring in hospital C, only one was the 'outbreak' strain (a relapsed patient who was part of the original episode). There were seven further cases in geriatric and medical wards of hospital A. All six typed isolates were also the outbreak strain. By chance, four isolates from hospital A and four from hospital B pre-dating the outbreak were also available for typing and seven of these were found to be identical to the outbreak strain. This suggests that one strain of C. difficile was endemic in geriatric and medical facilities on two sites and was responsible for nosocomial diarrhoea over at least one year. The problems of optimal management and infection control in this situation are discussed.

Aged↗

PubMed2001

Two consecutive nationwide outbreaks of Listeriosis in France, October 1999-February 2000.

In France, listeriosis surveillance is based on mandatory notification of all culture-confirmed cases, with systematic typing of isolates and routine collection of the patient's food history. From October 1999 to March 2000, two outbreaks of listeriosis were detected through this enhanced surveillance system. In outbreak 1, analysis of the food histories of cases suggested brand X "rillettes," a pâté-like meat product, as the vehicle of infection, and the outbreak strain of Listeria monocytogenes was subsequently isolated from the incriminated rillettes. In outbreak 2, a case-control study showed that consumption of jellied pork tongue was strongly associated with infection with the outbreak strain (odds ratio = 75.5, 95% confidence interval: 4.7, 1,216.0). However, trace-back results did not permit incrimination of any particular manufacturer of jellied pork tongue, and the outbreak strain was not isolated from the incriminated food or from any production sites. Consumption of jellied pork tongue was discouraged on epidemiologic evidence alone. The consecutive occurrence of these two outbreaks confirms the epidemic potential of listeriosis, even in a context of decreasing incidence, and underlines the importance of timely case-reporting and systematic typing of human L. monocytogenes strains to allow early detection and separate investigation of different clusters.

Animals↗

PubMed2004

Household outbreaks among culture-confirmed cases of bacterial gastrointestinal disease.

To examine the general frequency of household outbreaks, the authors performed a retrospective search among cases of the five most frequent gastrointestinal bacterial pathogens in Denmark, a country of 5.3 million inhabitants. This was done for 57,667 cases registered from 1991 to 2001 by finding all cases that shared addresses and became infected within 3 weeks of one another. The percentage of cases that were part of household outbreaks was found to be 3.2% for Campylobacter, 13.3% for Salmonella serotype Enteritidis, 5.6% for Salmonella serotype Typhimurium, 2.0% for Yersinia enterocolitica, and 10.4% for Shigella sonnei. The vast majority of the outbreaks had not previously been registered. The wide variation in the ability to cause household outbreaks among the different types of bacteria reflects differences in their epidemiology and most likely also mirrors their overall outbreak potential. Differences in the time occurring between infections of household members may also indicate differences in the importance of person-to-person transmission for the different types of bacteria. The fact that household outbreaks occur with a relatively high frequency may be utilized in future analyses of sources of infection, in particular of Campylobacter, for which more household outbreaks than expected were identified.

Bacterial Infections↗

PubMed1994

A comparative review of systemic and neurological symptomatology in 12 outbreaks collectively described as chronic fatigue syndrome, epidemic neuromyasthenia, and myalgic encephalomyelitis.

Outbreaks of illnesses of unknown etiology typified by a chronic relapsing course of constitutional symptoms and nervous system involvement have collectively been referred to as chronic fatigue syndrome, epidemic neuromyasthenia, and myalgic encephalomyelitis. To examine heterogeneity of clinical presentation, a comparative review was undertaken for 12 well-documented outbreaks reported since 1934. A systemic syndrome characterized by excessive fatigue, myalgias, headache, low-grade fever, and other constitutional symptoms was common to cases in all outbreaks. However, marked heterogeneity in the range of neurological features was apparent. On the basis of predominant neurological manifestations, outbreaks could be grouped into four levels of increasing neurological involvement: affective neuropsychological changes (level I); prominent cutaneous sensory symptoms with both affective and cognitive neuropsychological changes (level II); marked objective paresis with cutaneous sensory as well as affective and cognitive neuropsychological changes (level III); and cutaneous sensory, affective and cognitive neuropsychological, posterior column, cranial nerve, and mixed upper and lower motor neuron changes (level IV). Groups with the most prominent objective neurological findings (levels III and IV) comprised exclusively outbreaks reported between the 1930s and 1950s. All but one outbreak in groups with less prominent neurological findings (levels I and II) were reported between the 1960s and 1980s; a range of neurological features was observed for these groups. Because a complete neurological examination is not emphasized as part of the diagnostic workup in current outbreaks, it is possible that less obvious neurological findings may be overlooked. Careful evaluation of neurological features in epidemic and endemic cases of what is now called chronic fatigue syndrome may be one approach to distinguishing subtypes of what has been described in the past as a nosological entity.

Disease Outbreaks↗

PubMed1993

Characterization of Giardia duodenalis isolates from a waterborne outbreak.

Isolates were retrieved from drinking water and from animal and human sources associated with a waterborne outbreak of giardiasis. This is the first report of water-source and epidemic-associated Giardia isolates being adapted to in vitro propagation. Outbreak-associated, non-out-break-associated, and reference isolates were characterized using isoenzyme electrophoresis and pulsed-field gel electrophoresis (PFGE). All outbreak-associated and 2 other isolates were in one of eight zymodemes. The chromosomal complement of the outbreak-associated isolates was relatively homogeneous; this PFGE karyotype was distinguishable from other karyotypes. Overall results of both characterization methods were similar, although PFGE appears to be a more discriminating biotyping technique. Banding patterns of the outbreak-associated Giardia isolates remained the same even though the parasite passed through different hosts during the outbreak. Heterogeneity of isolates was also demonstrated for the first time within a single community not associated with the outbreak.

Age Factors↗

PubMed1990

Management of institutional outbreaks of Salmonella gastroenteritis.

The number of reports of outbreaks of salmonella gastroenteritis in hospitals has decreased since 1984 but the number of outbreaks in institutions such as old peoples' homes have increased during 1988. Foods, particularly chickens, remain a source of salmonellae and particular attention has to be paid to training and practices in food preparation areas. Staff who are convalescent are very unlikely to be sources of salmonella and do not need to be excluded unless they handle food that receives no further cooking. Outbreaks that do occur can usually be controlled by patient isolation and good control-of-infection measures and an effective Major Outbreak Control Plan is necessary. In some large old hospitals cross infection outbreaks may continue despite good control-of-infection measures. Antibiotics have been contraindicated in the treatment of salmonella gastroenteritis, but the new 4-quinolone antibiotics have demonstrated potential. Ciprofloxacin was used successfully in two outbreaks of salmonella gastroenteritis at a dose of 500 mg bd orally for seven days. Relapses did not occur and resistance did not develop. Ciprofloxacin should be considered as a therapeutic adjunct to control of infection measures in cross infection outbreaks in these situations.

Anti-Bacterial Agents↗

PubMed2001

Syphilis outbreak assessment.

BACKGROUND: Syphilis rates began to decline in 1991 and have decreased every year since. In 1998, 6,993 cases of primary and secondary syphilis were reported in the United States, for a national incidence of 2.6 cases per 100,000 population. Although syphilis rates are at an historic low, focal outbreaks still occur. On October 7, 1999, the Division of Sexually Transmitted Disease Prevention of the Centers for Disease Control and Prevention, in collaboration with federal and community partners, presented the National Plan for Elimination of Syphilis from the United States. One of the five key strategies of the plan is rapid outbreak response. METHODS: Methods for outbreak assessment and response were reviewed in the literature, synthesized, and adapted for use in syphilis outbreaks. RESULTS: Key elements of outbreak assessment and response are detection, surveillance data review, hypothesis generation, intervention development, and the evaluation of clinical, public health, and laboratory services. CONCLUSIONS: Outbreak response necessitates community participation and a coordinated interdisciplinary effort to determine social and behavioral contributors to the outbreak and to develop targeted interventions.

Centers for Disease Control and Prevention, U.S.↗

PubMed2005

Vaccine effectiveness and severity of varicella among previously vaccinated children during outbreaks in day-care centers with low vaccination coverage.

BACKGROUND: Varicella vaccine effectiveness (VE) during outbreaks has been reported to be 71-100% against any disease and >90% against moderate/severe disease even in day-care centers (DCCs) and schools with low vaccination rates. A recent report suggested an effectiveness rate of 44% during a DCC outbreak despite a high vaccination rate. AIMS: To reassess vaccination coverage, VE and severity of disease among previously vaccinated children after exposure during DCC outbreaks in northern Israel, where vaccination rates are low. METHODS: During January to June 2003, active surveillance for varicella among children in northern Israel revealed outbreaks in 8 DCCs with children 3-6 years of age. Data concerning symptoms of the disease and the age at vaccination (for previously vaccinated children) were obtained from parents and health care providers for children who contracted the disease. Analysis of VE was limited to children who were continuously enrolled in DCCs during the outbreaks. RESULTS: The overall vaccination rate was 37%. The incidences of natural varicella and breakthrough varicella (BV) were 79 of 153 [52%; 95% confidence interval (CI) 44-60%] and 37 of 89 (41.5%; 95% CI 31-52%), respectively. VE was 20% (95% CI 0-40%) against disease of any severity and 93.4% (95% CI 75-98%) against moderate/severe disease. Ninety-four percent and 14% of children with BV and natural varicella, respectively, had mild disease (P < 0.001). The odds ratio for BV was 17 (95% CI 2.18-118) for children vaccinated >2 years before the outbreak. CONCLUSIONS: During varicella outbreaks in DCCs with low vaccine coverage, previous vaccination provided poor protection against chickenpox, mostly among children who had been vaccinated >2 years earlier, but the disease appeared to be much milder among children with BV than among nonvaccinated children.

Age Distribution↗

PubMed2005

Clinical and economic effects of pertussis outbreaks.

BACKGROUND: The reported incidence of pertussis is increasing, especially among the adolescent population. Current outbreak management strategies include investigating cases, contact follow-up, diagnostic testing, and antibiotic prophylaxis and treatment. The cost of these methods is substantial and can be attributed to the mobilization within public health departments to control the outbreaks. METHODS: Through an extensive review of the literature, the clinical and economic effects of pertussis outbreaks in various nonhousehold settings are discussed. RESULTS: The reported incidence of pertussis among adolescents and adults in the United States since the early 1980s continues to rise. The challenges of preventing and controlling pertussis outbreaks involve diagnosing pertussis in a timely, accurate, and standardized fashion and understanding the true burden of disease in different age and socioeconomic groups. The economic effects of pertussis have been demonstrated to be significant to individuals and communities, both locally and globally. Costs associated with pertussis often include diagnostic testing, hospitalization, emergency and/or medical office visits, antibiotic and symptomatic treatment, lost work days, and other reductions in productivity. In outbreak settings, increased surveillance, antibiotic prophylaxis, isolation of infected cases, and enhanced communication and education add to the economic burden of this disease. The potential opportunity to apply the use of pertussis booster vaccination to these populations, particularly among adolescents, likely would reduce the occurrence of pertussis and minimize the clinical and economic repercussions of pertussis outbreaks. CONCLUSIONS: In the near future, it is anticipated that evaluating the effects of a licensed acellular pertussis booster vaccine in persons > or =10 years of age will become routine in pertussis prevention and outbreak-control activities.

Adolescent↗

PubMed2007

Elimination of hepatitis a infection outbreaks in day care and school settings in southern Israel after introduction of the national universal toddler hepatitis a immunization program.

BACKGROUND: In 1999, Israel became the first country to begin universal toddler immunization against hepatitis A infection with a 2-dose schedule at 18 and 24 months. The effect of the Israeli program on outbreaks of Hepatitis A in day care and school settings was studied. METHODS: The records of all hepatitis A illness outbreaks in day care and school settings reported to the Ministry of Health in Southern Israel during 1993 through 2005 were reviewed. The number of exposed contacts for whom postexposure prophylaxis was administered was retrieved from records of epidemiologic investigations. Rates of immunization coverage were extracted from records of Maternal and Child Health Clinics. RESULTS: Three hundred nineteen cases of hepatitis A illness during the years 1993 through 2005 were associated with 113 outbreaks in day care and school settings of which 92% occurred before the institution of universal toddler immunization. Since 2000, no hepatitis A infection outbreaks have been reported in any day care and school settings in the region. An average of 732 children received immunoglobulin prophylaxis yearly because of exposure to an outbreak in an educational setting during the preimmunization period, 106 in 2000 and zero in the 5 years since 2001. The data showed marked herd immunity since school-aged children born before 1999 were not immunized, but elimination of outbreaks occurred equally in that age group. Immunization coverage was 86.4% for one dose of hepatitis A vaccine by age 3 years and 77.3% for 2 doses among the birth cohort of 2000. CONCLUSIONS: Universal hepatitis A immunization of toddlers was associated with disappearance of outbreaks in educational settings. This included cohorts of nonimmunized children representing marked herd immunity.

Adolescent↗

PubMed2003

Outbreak of invasive disease caused by methicillin-resistant Staphylococcus aureus in neonates and prevalence in the neonatal intensive care unit.

OBJECTIVES: To describe an outbreak of severe invasive disease caused by methicillin-resistant Staphylococcus aureus (MRSA) and the epidemiology of MRSA in a neonatal intensive care unit during a 12-yr period from 1989 to 2001. SETTING: A 40-bed, level III neonatal intensive care unit at a children's hospital that admits approximately 450 neonates each year from about 35 neighboring hospitals. PATIENTS: All neonates infected or colonized with MRSA during the outbreak are described. All cases of MRSA infection or colonization in the neonatal intensive care unit from 1989 to 2001 were identified from the database maintained by the hospital epidemiology program. RESULTS: During the outbreak, 12 neonates were infected or colonized with MRSA, 11 of whom had the epidemic strain. Seven of these 11 neonates had invasive disease, including bacteremia, meningitis, or urinary tract infection, and four neonates were colonized with the epidemic strain. This outbreak was difficult to control by routine epidemiologic measures, and additional control measures, including closing the neonatal intensive care unit to new admissions and treating all infants with intranasal mupirocin, were implemented. Since the outbreak, the prevalence of MRSA in the neonatal intensive care unit has remained low. CONCLUSIONS: MRSA outbreaks in neonatal intensive care units can be prolonged. Aggressive infection-control measures are often necessary to terminate these outbreaks. Such efforts are essential because MRSA infections in premature neonates can cause significant morbidity and mortality.

Cross Infection↗

PubMed2004

The experience of the 2003 SARS outbreak as a traumatic stress among frontline healthcare workers in Toronto: lessons learned.

The outbreak of severe acute respiratory syndrome (SARS) in the first half of 2003 in Canada was unprecedented in several respects. Understanding the psychological impact of the outbreak on healthcare workers, especially those in hospitals, is important in planning for future outbreaks of emerging infectious diseases. This review draws upon qualitative and quantitative studies of the SARS outbreak in Toronto to outline the factors that contributed to healthcare workers' experiencing the outbreak as a psychological trauma. Overall, it is estimated that a high degree of distress was experienced by 29-35% of hospital workers. Three categories of contributory factors were identified. Relevant contextual factors were being a nurse, having contact with SARS patients and having children. Contributing attitudinal factors and processes were experiencing job stress, perceiving stigmatization, coping by avoiding crowds and colleagues, and feeling scrutinized. Pre-existing trait factors also contributed to vulnerability. Lessons learned from the outbreak include: (i) that effort is required to mitigate the psychological impact of infection control procedures, especially the interpersonal isolation that these procedures promote; (ii) that effective risk communication is a priority early in an outbreak; (iii) that healthcare workers may have a role in influencing patterns of media coverage that increase or decrease morale; (iv) that healthcare workers benefit from resources that facilitate reflection on the effects of extraordinary stressors; and (v) that healthcare workers benefit from practical interventions that demonstrate tangible support from institutions.

Disease Outbreaks↗

PubMed1997

Epidemiological analysis of strains of Salmonella enterica serotype Enteritidis from foodborne outbreaks occurring in Italy, 1980-1994.

Polymerase chain reaction (PCR-) ribotyping was performed on 243 strains of Salmonella enterica serotype Enteritidis isolated during the years 1980-1994 from 58 foodborne outbreaks occurring in different regions of Italy. The majority (37) of the outbreaks were attributed to phage type (PT) 4, followed by PT1 (seven outbreaks); the latter was identified in 1993 in Italy in epidemic strains of Enteritidis. In eight cases more than one phage type was recognised from a single event. Nine PCR-ribotypes (PCR-RTs) were detected, with a strong prevalence of PCR-RTs f7 and e5 (23 and 21 outbreaks, respectively). In two instances two distinct PCR-RTs were identified within strains from a single outbreak. All but one of the PT1 outbreaks were caused by PCR-RT f7, whereas PT4 outbreaks could be subdivided into six subsets. Clustering of isolates was consistent with data obtained from epidemiological investigations. PCR-ribotyping proved to be an effective and reliable tool for subtyping isolates of Enteritidis belonging to the most frequent phage types. Nevertheless, in terms of laboratory expertise and lack of inter-laboratory standardisation, this typing technique is best suited for reference laboratories.

Animals↗

PubMed1998

Identification of nasopharyngeal carriage of an outbreak strain of Neisseria meningitidis by pulsed-field gel electrophoresis versus phenotypic methods.

The clustering of four cases of meningococcal disease during a 3-month period in a small community with 2233 inhabitants prompted an interventional carrier survey in persons < 19 years old and in family members of the patients. The aims of the survey were to identify the nasopharyngeal carriers and the carriage rate of the outbreak strain, to offer chemoprophylaxis to those carrying the outbreak strain, and to study the discriminatory power of phenotypic methods versus pulsed-field gel electrophoresis (PFGE) on carrier isolates during an outbreak. A high percentage of the population in the age group 0-19 years (73.7%) participated in the study. Among the 469 samples collected in this age group, meningococci were grown from 43 (9.2%). The highest carriage rates were in the age group 18-19 years (36.4%). With a provisional definition of the outbreak strain (group B or non-groupable Neisseria meningitidis with reduced sulphonamide sensitivity), six carriers were identified. All were treated with a single dose of ofloxacin. Four of these persons (0.76% of all tested) were later shown to have harboured the outbreak strain when analysed by PFGE. Three of them were epidemiologically closely related to one of the index cases. Serogrouping alone is not sufficient for the identification of an epidemic strain of N. meningitidis. Complete concordance of type and subtype antigens correctly identified the outbreak strain in this study. PFGE is well suited for the identification of an outbreak strain of N. meningitidis versus non-epidemic strains in tonsillo-pharyngeal specimens.

Adolescent↗

PubMed2004

Parvovirus B19 infection in medical students during a hospital outbreak.

From March to May 2002, a parvovirus B19 (B19) outbreak was identified at a general hospital that serves as a teaching facility for the Universidad Autónoma de San Luis Potosí, Mexico. Medical students attending the hospital presented with symptoms suggestive of B19 infection. Previous studies have suggested that apparent hospital-related B19 outbreaks may be a reflection of B19 infection in the community. A study was undertaken to assess whether exposure to the hospital was a risk factor for B19 infection and to determine to what extent medical students were infected during this outbreak. The incidence of B19 infection in medical students attending the teaching hospital during the outbreak (n=211) was determined and compared to students not attending the hospital (n=96). To assess if a community-wide outbreak had occurred, 80 blood donors were also evaluated for the presence of B19 antibodies. Acute B19 infection was identified in 40 of 119 (33.6%) susceptible students attending the hospital and in 20 of 47 (42.6%) susceptible students not attending the hospital. The frequency of acute infection among susceptible blood donors was lower (9.5%) than in students, but higher than the rate expected during non-epidemic periods. Most infections (68.3%) were asymptomatic. Symptoms reported by infected subjects were not specific for B19 infection. Only 11.7% of subjects with acute infection fulfilled the clinical surveillance definition used to detect cases during the outbreak. In conclusion, hospital exposure was not associated to increased risk of B19 infection among medical students. Medical students may be at increased risk for acquiring and transmitting B19 infection during outbreaks.

Adolescent↗

PubMed2004

An outbreak of leptospirosis in Orissa, India: the importance of surveillance.

OBJECTIVE: To demonstrate the importance of surveillance systems in detecting emerging diseases and highlighting the strengths and weaknesses of an existing one. METHODS: The Orissa multi-disease surveillance system (OMDSS) was introduced in November 1999. Reporting units from the periphery send data to the district on a weekly basis. These reports are analysed regularly. A district task force (DTF) was available to intervene in the event of an outbreak. The OMDSS detected an increasing number of cases with fever and jaundice in June 2002. The DTF investigated this outbreak using clinical, epidemiological and laboratory tools to identify its cause. RESULTS: This outbreak, in a remote corner of India, was detected within 4 days by an existing surveillance system. Action was initiated within 24 h, but it took approximately two more weeks for the causative agent to be diagnosed. A total of 143 people were suspected to have leptospirosis between 23 June 2002 and 31 July 2002. The attack rate was 5.95% and the case fatality ratio (CFR) was 7.69%, both lower than outbreaks reported elsewhere in India. While males were infected more often than females, the CFR was higher among females and among the 6-15 year age groups. Exposure to infected water in a canal was the probable cause of the outbreak. IgM antibodies were positive in 33 of the patients and six patients tested positive for PCR and culture. Leptospirosis interrogans serovar canicola, Leptospirosis interrogans serovar pomona and Leptospirosis interrogans serovar hebdomadis were isolated. CONCLUSIONS: Leptospirosis is a new disease in this region of India. This outbreak was detected and diagnosed because of the surveillance system. The prompt response helped in containing the outbreak early enough. However, the morbidity and mortality could have been further mitigated if the delays in transmitting information had been minimized. An adequate laboratory support would have also helped considerably. We conclude stressing the importance of surveillance as a public health tool.

Adolescent↗

PubMed2006

Short communication: Strengthening sub-national communicable disease surveillance in a remote Pacific Island country by adapting a successful African outbreak surveillance model.

Successful communicable disease surveillance depends on effective bidirectional information flow between clinicians at the periphery and communicable disease control units at regional, national and global levels. Resource-poor countries often struggle to establish and maintain the crucial link with the periphery. A simple syndrome-based outbreak surveillance system initially developed and evaluated in Mpumalanga Province, South Africa was adapted for the Pacific island nation of Tuvalu. Eight syndromes were identified for surveillance: acute flaccid paralysis (poliomyelitis), profuse watery diarrhoea (cholera), diarrhoea outbreak, dysentery outbreak, febrile disease with abdominal symptoms and headache (typhoid), febrile disease with generalized non-blistering rash (measles), febrile disease with intense headache and/or neck stiffness with or without haemorrhagic rash (meningococcal meningitis), and outbreaks of other febrile diseases of unknown origin. A user-oriented manual, the Tuvalu Outbreak Manual (http://www.wepi.org/books/tom/), was developed to support introduction of the surveillance system. Nurses working in seven outer island clinics and the hospital outpatient department on the main island rapidly report suspected outbreaks and submit weekly zero-reports to the central communicable disease control unit. An evaluation of the system after 12 months indicated that the Outbreak Manual was regarded as very useful by clinic nurses, and there was early evidence of improved surveillance and response to the disease syndromes under surveillance.

Cholera↗

PubMed2001

February asthma outbreaks in NSW: a case control study.

OBJECTIVES: To investigate individual factors associated with an asthma outbreak among children aged one to 14 years in Sydney in February 1999. METHODS: A case control study was undertaken with cases (n=92) defined as all children admitted to Sydney Children's Hospital for asthma in February 1999. Unmatched controls (n=76) were all children admitted for asthma in the previous three months. We obtained information by a structured telephone survey of parents. Logistic regression analyses were used to determine odds ratios for risk factors for hospital admission. RESULTS: Mean age for hospital admission of 4.7 years for cases and 4.4 years for controls. The presence of one or more siblings reduced the risk of admission during an asthma outbreak (OR=0.59, 95% CI 0.37 to 0.93). Children with older siblings aged 10 to 14 years were also less likely to be admitted (OR=0.3, 95% CI 0.12 to 0.74). An age effect was observed. Other demographic, clinical and environmental characteristics, including smoking, were not associated with admission during the outbreak. CONCLUSIONS: The main findings of this study are the protective effect of siblings and an age-dependent effect in risk of hospital admission during an asthma outbreak. These findings are consistent with an infective cause of the outbreak. IMPLICATIONS: Children without siblings, particularly older siblings, appear to be at highest risk of hospital admission during an asthma outbreak. Environmental and other factors need to be examined to further explain the episodicity of such outbreaks and to determine means of predicting and preventing future episodes.

Adolescent↗