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PubMed2003

Two epidemiologic patterns of norovirus outbreaks: surveillance in England and wales, 1992-2000.

In the period 1992-2000, the Public Health Laboratory Service Communicable Disease Surveillance Centre collected standardized epidemiologic data on 1,877 general outbreaks of Norovirus (formerly "Norwalk-like virus") infection in England and Wales. Seventy-nine percent of general outbreaks occurred in health-care institutions, i.e., hospitals (40%) and residential-care facilities (39%). When compared with outbreaks in other settings, those in health-care institutions were unique in exhibiting a winter peak (p<0.0001); these outbreaks were also associated with significantly higher death rates and prolonged duration but were smaller in size and less likely to be foodborne. These data suggest that Norovirus infection has considerable impact on the health service and the vulnerable populations residing in institutions such as hospitals and residential homes. A distinct outbreak pattern in health-care institutions suggests a combination of host, virologic, and environmental factors that mediate these divergent epidemiologic patterns.

Aged↗

PubMed2003

Viral gastroenteritis outbreaks in Europe, 1995-2000.

To gain understanding of surveillance and epidemiology of viral gastroenteritis outbreaks in Europe, we compiled data from 10 surveillance systems in the Foodborne Viruses in Europe network. Established surveillance systems found Norovirus to be responsible for >85% (N =3,714) of all nonbacterial outbreaks of gastroenteritis reported from 1995 to 2000. However, the absolute number and population-based rates of viral gastroenteritis outbreaks differed markedly among European surveillance systems. A wide range of estimates of the importance of foodborne transmission were also found. We review these differences within the context of the sources of outbreak surveillance information, clinical definitions, and structures of the outbreak surveillance systems.

Data Collection↗

PubMed2003

Automated, laboratory-based system using the Internet for disease outbreak detection, the Netherlands.

Rapid detection of outbreaks is recognized as crucial for effective control measures and has particular relevance with the recently increased concern about bioterrorism. Automated analysis of electronically collected laboratory data can result in rapid detection of widespread outbreaks or outbreaks of pathogens with common signs and symptoms. In the Netherlands, an automated outbreak detection system for all types of pathogens has been developed within an existing electronic laboratory-based surveillance system called ISIS. Features include the use of a flexible algorithm for daily analysis of data and presentation of signals on the Internet for interpretation by health professionals. By 2006, the outbreak detection system will analyze laboratory-reported data on all pathogens and will cover 35% of the Dutch population.

Algorithms↗

PubMed2003

Lessons from the severe acute respiratory syndrome outbreak in Hong Kong.

Severe acute respiratory syndrome (SARS) is now a global public health threat with many medical, ethical, social, economic, political, and legal implications. The nonspecific signs and symptoms of this disease, coupled with a relatively long incubation period and the initial absence of a reliable diagnostic test, limited the understanding of the magnitude of the outbreak. This paper outlines our experience with public health issues that have arisen during this outbreak of SARS in Hong Kong. We confirmed that case detection, reporting, clear and timely dissemination of information, and strict infection control measures are essential in handling such an infectious disease outbreak. The need for an outbreak response unit is crucial to combat any future outbreak.

Animals↗

PubMed2004

Candida parapsilosis characterization in an outbreak setting.

Candida parapsilosis is an important non-albicans species which infects hospitalized patients. No studies have correlated outbreak infections of C. parapsilosis with multiple virulence factors. We used DNA fingerprinting to determine genetic variability among isolates from a C. parapsilosis outbreak and from our clinical database. We compared phenotypic markers of pathogenesis, including adherence, biofilm formation, and protein secretion (secretory aspartic protease [SAP] and phospholipase). Adherence was measured as colony counts on silicone elastomer disks immersed in agar. Biofilms formed on disks were quantified by dry weight. SAP expression was measured by hydrolysis of bovine albumin; a colorimetric assay was used to quantitate phospholipase. DNA fingerprinting indicated that the outbreak isolates were clonal and genetically distinct from our database. Biofilm expression by the outbreak clone was greater than that of sporadic isolates (p < or =0.0005). Adherence and protein secretion did not correlate with strain pathogenicity. These results suggest that biofilm production plays a role in C. parapsilosis outbreaks.

Aspartic Acid Endopeptidases↗

PubMed2005

Surveillance and control measures during smallpox outbreaks.

We reviewed historical data from 2 smallpox outbreaks in Liverpool and Edinburgh during the early and middle years of the 20th century to assess their contribution to developing modern strategies for response to a deliberate release of smallpox virus. Reports contemporaneous to these outbreaks provide detail on the effectiveness of public health interventions. In both outbreaks, extensive contact tracing, quarantine, and staged vaccination campaigns were initiated, and the outbreaks were controlled within 15 months and 3 months, respectively. In Edinburgh, the number of fatalities associated with vaccination exceeded the number of deaths from the disease. In Liverpool, ambulatory, vaccine-modified cases and misdiagnosis as chickenpox resulted in problems with outbreak control. The relatively slow spread of smallpox, as exemplified by the report from Liverpool, allowed for effective implementation of targeted intervention methods. Targeted surveillance and containment interventions have been successful in the past and should be explored as alternatives to mass vaccination.

Adolescent↗

PubMed2005

Epidemiology of Escherichia coli O157:H7 outbreaks, United States, 1982-2002.

Escherichia coli O157:H7 causes 73,000 illnesses in the United States annually. We reviewed E. coli O157 outbreaks reported to Centers for Disease Control and Prevention (CDC) to better understand the epidemiology of E. coli O157. E. coli O157 outbreaks (>or=2 cases of E. coli O157 infection with a common epidemiologic exposure) reported to CDC from 1982 to 2002 were reviewed. In that period, 49 states reported 350 outbreaks, representing 8,598 cases, 1,493 (17%) hospitalizations, 354 (4%) hemolytic uremic syndrome cases, and 40 (0.5%) deaths. Transmission route for 183 (52%) was foodborne, 74 (21%) unknown, 50 (14%) person-to-person, 31 (9%) waterborne, 11 (3%) animal contact, and 1 (0.3%) laboratory-related. The food vehicle for 75 (41%) foodborne outbreaks was ground beef, and for 38 (21%) outbreaks, produce.

Animals↗

PubMed1997

A community-wide hepatitis A outbreak in the Shoalhaven region, New South Wales.

We investigated a community-wide outbreak of hepatitis A virus infection in the Shoalhaven region of the New South Wales south coast. Epidemiological features of the outbreak suggested that transmission was predominantly person-to-person. These included: the prolonged course of the epidemic, the bimodal age-specific attack rate, the lower socioeconomic risk groups affected, and the large proportion of cases who reported prior contact with another case. Although widespread use of post-exposure immunoprophylaxis appeared to be effective in preventing symptomatic infection in individuals, it did not rapidly halt the outbreak. We review methods of mass intervention for community-wide outbreaks of hepatitis A virus infection, and define priorities for investigation of future outbreaks.

Disease Outbreaks↗

PubMed1997

An outbreak of influenza B among workers on an oil rig.

An outbreak of influenza B occurred in December 1996 on an oil rig in Darwin Harbour. The outbreak affected 56% of the workers on the rig. An outbreak in December is outside the usual Australian influenza season of June to September, but is consistent with other tropical regions, where outbreaks can occur throughout the year. Influenza vaccination could prevent similar outbreaks in confined workplaces.

Disease Outbreaks↗

PubMed2002

A large, prolonged outbreak of human calicivirus infection linked to an aged-care facility.

This report investigates an outbreak of acute gastrointestinal illness, microbiologically and epidemiologically linked to an aged-care facility and seeks to determine if there was a point source of infection. A register of cases that included onset date and time of illness and symptoms was maintained by nursing staff. Faecal specimens were tested for conventional gastrointestinal pathogens and for human calicivirus (HuCV). There were 81 cases reported. Specimens were received for testing from 25 cases. Twenty-three of the 25 (92%) specimens were positive for HuCV RNA by reverse transcriptase polymerase chain reaction (RT-PCR). The 2 negative samples contained RT-PCR inhibitors. Descriptive epidemiology suggested that staffing practices were important in prolonging the outbreak. No point source of infection was identified. Instead environmental contamination, aerosol transmission and work practices that fail to take account of the natural history of HuCV infection probably contributed to the size (81 cases) and duration (3 weeks) of this outbreak among the residents, staff and visitors of an aged-care facility and their contacts. Institutional outbreaks caused by HuCV, formerly called Norwalk-like or small round structured viruses, are extremely difficult to control. Infected staff may contribute significantly to the amplification of outbreaks. Rapid confirmation of HuCV infection is now routinely possible using polymerase chain reaction diagnostics but progress in laboratory technology has not yet translated into faster or more effective interventions.

Acute Disease↗

PubMed2003

Screening and electronic labelling of ward contacts of vancomycin-resistant Enterococcus faecium vanB carriers during a single-strain hospital outbreak and after discharge from hospital.

A large single-strain outbreak of vancomycin-resistant Enterococcus faecium (VREF) vanB occurred in Royal Perth Hospital from July to December 2001. When a VREF-carrying patient was discovered on a ward, all patients on the ward were screened with rectal swabs. A total of 172 patients were colonised, four with infections, but no deaths were attributable to VREF. The number of rectal swabs required to detect each carrier was recorded. On average four rectal swabs, each collected on separate days, were needed to detect more than 90 per cent of the 172 VREF carriers who were epidemiologically linked to the Royal Perth Hospital outbreak. An electronic alert system (Micro-Alert) was used to identify ward contacts of VREF carriers and enabled those who had not been screened before discharge to be followed-up and screened. Ninety-six contacts were actively followed-up in October 2001 and 32 (33.3%) were found to be VREF carriers. From 28 September 2001 to 30 April 2002, a total of 1,977 ward contacts were screened after discharge from hospital and 54 (2.73%) were found to be carrying VREF. We conclude that during single-strain outbreaks of vancomycin-resistant enterococci in hospitals, patient contacts need to be screened on more than three occasions in order to detect most of the carriers and control the outbreak. Secondly, electronic labelling and active follow-up of ward contacts of VREF carriers resulted in a significant number of carriers being detected who otherwise posed a risk of initiating further outbreaks in hospitals if they were readmitted.

Carrier State↗

PubMed2005

Epidemiological features and control of an outbreak of scarlet fever in a Perth primary school.

Scarlet fever was associated with feared outbreaks and mortality in the 19th Century. It occurs sporadically in modern society and infection is readily treated with antibiotics. We report on a scarlet fever outbreak in children attending a primary school in Perth, Western Australia, in late 2003. A total of 13 cases were identified over a five week period. Six of the cases were pre-primary children (ages 4 to 5) from the same class of 26 children (attack rate 23.1%). Three of the remaining seven cases were older siblings of pre-primary cases who developed scarlet fever after their younger siblings. Screening of the children and teachers from the two pre-primary classes at the school yielded 12 positive pharyngeal swabs for group A Streptococcus. Emm-typing of the screening isolates indicated that a common strain was circulating within the outbreak pre-primary class, with four of six isolates identified as emm-type 3. The overall group A Streptococcus carriage rate in screened students in this class was 31.6 per cent and the carriage rate for emm-type 3 was 21.1 per cent. Carriers were treated with oral penicillin V to eradicate carriage and control the outbreak. No further cases of scarlet fever were reported after the treatment of pharyngeal carriers. Outbreaks of scarlet fever still occur in young children and identification and treatment of carriers may still be valuable.

Carrier State↗

PubMed2006

Campylobacter outbreak due to chicken consumption at an Australian Capital Territory restaurant.

Campylobacter is the most common cause of bacterial gastroenteritis in Australia, with 15,008 notifications in 2004. This represents only a small fraction of the total cases of Campylobacter. Despite this, outbreaks are rarely reported. This report describes the investigation of an outbreak of campylobacteriosis following a restaurant meal in the Australian Capital Territory. The outbreak was identified by a general practitioner who notified the Health Protection Service, ACT Health. A retrospective cohort investigation of the 27 work colleagues who attended lunch at the restaurant was conducted. Eleven cases were identified with two culture positive for Campylobacter. An association between eating several dishes containing chicken was identified. This outbreak highlights the important identified risk for Campylobacter infection from commercially prepared chicken. It also demonstrates the important role of clinicians in notifying disease outbreaks.

Adult↗

PubMed2006

Impact of a mass immunization campaign to control an outbreak of severe respiratory infections in Nunavik, northern Canada.

OBJECTIVES: In spring 2002, a mass immunization campaign using a 23-valent pneumococcal polysaccharide vaccine (23-PPV) was launched in order to control an outbreak of severe pneumonia caused by a virulent clone of serotype 1 Streptococcus pneumoniae in Nunavik, Quebec, Canada. The objective of the study was to evaluate the impact of this campaign on the incidence of invasive pneumococcal disease (IPD) and hospitalizations possibly associated with pneumococcal infections (HPAPI) in the mostly Inuit population aged 10 to 64 years. STUDY DESIGN: Retrospective analysis of surveillance and administrative data. METHODS: Multivariate Poisson model comparing the frequency rates of selected outcomes before the outbreak, during the outbreak, and after implementation of the mass immunization program. RESULTS: The reported incidence of serotype 1 IPD decreased markedly after the implementation of the vaccination campaign (rate ratio = 0.16; p < 0.002). The frequency of HPAPI and the mean duration of hospital stay also decreased. However, vaccine failures were documented and the HPAPI rate remained higher than in the period prior to the outbreak. CONCLUSIONS: Although 23-PPV contributed to control the outbreak, better vaccines are needed for the prevention of infections caused by serotype 1 S. pneumoniae.

Adolescent↗

PubMed1998

First recorded outbreak of yellow fever in Kenya, 1992-1993. II. Entomologic investigations.

The first recorded outbreak of yellow fever in Kenya occurred from mid-1992 through March 1993 in the south Kerio Valley, Rift Valley Province. We conducted entomologic studies in February-March 1993 to identify the likely vectors and determine the potential for transmission in the surrounding rural and urban areas. Mosquitoes were collected by landing capture and processed for virus isolation. Container surveys were conducted around human habitation. Transmission was mainly in woodland of varying density, at altitudes of 1,300-1,800 m. The abundance of Aedes africanus in this biotope, and two isolations of virus from pools of this species, suggest that it was the principal vector in the main period of the outbreak. A third isolate was made from a pool of Ae. keniensis, a little-known species that was collected in the same biotope. Other known yellow fever vectors that were collected in the arid parts of the valley may have been involved at an earlier stage of the epidemic. Vervet monkeys and baboons were present in the outbreak area. Peridomestic mosquito species were absent but abundant at urban sites outside the outbreak area. The entomologic and epidemiologic evidence indicate that this was a sylvatic outbreak in which human cases were directly linked to the epizootic and were independent of other human cases. The region of the Kerio Valley is probably subject to recurrent wandering epizootics of yellow fever, although previous episodes of scattered human infection have gone unrecorded. The risk that the disease could emerge as an urban problem in Kenya should not be ignored.

Adolescent↗

PubMed1999

Molecular epidemiology of cryptosporidiosis outbreaks and transmission in British Columbia, Canada.

Isolates from 25 (13 sporadic and 12 outbreak) cryptosporidiosis cases, 24 of which were from British Columbia, Canada, were characterized using nested polymerase chain reaction amplification of the polymorphic internal transcribed spacer 1 locus. Two predominant Cryptosporidium parvum genotypes were found. Twelve (8 sporadic and 4 outbreak) isolates amplified with the cry7/cry21 primer pair and 12 (5 sporadic and 7 outbreak) isolates amplified with the cry7/cryITS1 primer pair. Multi-locus gene analysis using sequence polymorphisms on 3 other loci, i.e., the thrombospondin-related adhesion protein gene, the dihydrofolate reductase gene, and the 18S rRNA gene on 8 (4 outbreak and 4 sporadic) isolates showed non-random association among the human and animal alleles of the 4 different C. parvum gene loci. Associations between these 2 parasite genotypes and different routes of cryptosporidiosis transmission such as zoonotic, anthroponotic, and waterborne transmission were studied using municipal population and agricultural information, as well as detection of C. parvum oocysts in municipal drinking water specimens of the residential communities of sporadic and outbreak cases.

Animals↗

PubMed2000

Vector densities that potentiate dengue outbreaks in a Brazilian city.

To identify the critical vector density that potentiates dengue outbreaks in an endemic site and to identify obstacles to anti-dengue activities, we correlated a series of dengue outbreaks in a Brazilian city with the intensity of its anti-vector source-reduction activities. The proportion of houses infested by vector mosquitoes correlated inversely with intensity of anti-mosquito interventions, and the vector population developed independently of rainfall. Local periods of drought promoted vector abundance in two ways: residents stored water in which vector mosquitoes could breed, and cholera outbreaks due to contaminated water diverted local health workers from routine anti-vector activities. One dengue outbreak became apparent to authorities more than two months after it commenced but would have been identified almost immediately had dengue-like disease in indicator hospitals been monitored. Active surveillance, therefore, offers a window of opportunity for promptly executed anti-dengue interventions. Source-reduction measures that suppress vector infestations to less than 1% of houses effectively avert outbreaks of dengue.

Animals↗

PubMed2000

Epidemiology of cholera outbreak in Kampala, Uganda.

OBJECTIVE: To provide epidemiological description of the cholera outbreak which occurred in Kampala between December 1997 and March 1998. DESIGN: A four-month cross-sectional survey. SETTING: Kampala city, Uganda. MAIN OUTCOME MEASURES: Number of cases reported per day, attack rate per age group and per parish, case fatality ratio. RESULTS: The cholera outbreak was due to Vibrio cholerae O1 El Tor, serotype Ogawa. Between December 1997 and March 1998, 6228 cases of cholera were reported, of which 1091 (17.5%) were children under five years of age. The overall attack rate was 0.62%, similar in the under-fives and five and above age groups. The case fatality ratio among hospitalised patients was 2.5%. The peak of the outbreak was observed three weeks after the report of the first case, and by the end of January 1998 (less than two months after the first case), 88.4% of the cases had already been reported. The occurrence of cases concentrated in the slums where the overcrowding and the environmental conditions resembled a refugee camp situation. CONCLUSION: The explosive development of the cholera outbreak in Kampala, followed by a rapid decrease of the number of cases reported is unusual in a large urban setting. It appeared that each of the affected slums developed a distinct outbreak in a non immune population, which did not spread to contiguous areas. Therefore, we believe that, a decentralised strategy, that would focus the interventions on each heavily affected area, should be considered in these circumstances.

Adolescent↗