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PubMed2004

An outbreak of gastroenteritis during school trip caused by serotype G2 group A rotavirus.

Between May14 and 18, 2001, there was an outbreak of acute gastroenteritis involving 45 school children out of a total of 107 (aged 11-12 years) attending a 3-day school trip. The epidemic curve characterized by a rapid onset and decline with a single peak incidence over a 5-day period resembled the pattern typical of a food-borne gastroenteritis outbreak. Epidemiological and virological investigations concluded, however, that this outbreak was caused by a single strain of serotype G2 group A rotavirus spreading to schoolmates from the primary case-pupil who had already been ill at the start of the trip. Efficient person-to-person transmission was likely to have occurred due to prolonged and close contacts under the conditions typical of such school trips. This study emphasizes the importance of including group A rotavirus infection as a possible cause of gastroenteritis outbreaks even in older children and adults.

Child↗

PubMed2007

Predicting case numbers during infectious disease outbreaks when some cases are undiagnosed.

We describe a method for calculating 95 per cent bounds for the current number of hidden cases and the future number of diagnosed cases during an outbreak of an infectious disease. A Bayesian Markov chain Monte Carlo approach is used to fit a model of infectious disease transmission that takes account of undiagnosed cases. Assessing this method on simulated data, we find that it provides conservative 95 per cent bounds for the number of undiagnosed cases and future case numbers, and that these bounds are robust to modifications in the assumptions generating the simulated data. Moreover, the method provides a good estimate of the initial reproduction number, and the reproduction number in the latter stages of the outbreak. Applying the approach to SARS data from Hong Kong, Singapore, Taiwan and Canada, the bounds on future diagnosed cases are found to be reliable, and the bounds on hidden cases suggests that there were few hidden cases remaining at the end of the outbreaks in each region. We estimate that the initial reproduction numbers lay between 1.5 and 3, and the reproduction numbers in the later stages of the outbreak lay between 0.36 and 0.6.

Bayes Theorem↗

PubMed2006

Automated detection of infectious disease outbreaks: hierarchical time series models.

The purpose of infectious disease surveillance is to inform the public health policy makers on the incidence and trends of infectious diseases and to trigger appropriate actions to control infectious disease outbreaks. The enormous amount of data collected with automated laboratory-based surveillance systems require automated algorithms for detecting unexpected aberrations that may signal infectious disease outbreaks. In this paper, we explore the potential of hierarchical time series models to detect deviations from expected incidence. As these count data are extremely noisy it can be expected that these models are suitable to detect signal from noise and accommodate for possible autocorrelation. The proposed procedure consists of three steps; (1) the model parameters are estimated by empirical Bayes on a training period of, e.g. a year; (2) the expected values are updated for small time steps (e.g. daily) as new data arrive; (3) threshold levels are updated conditionally on the past expected values and an alarm is triggered when the threshold level is exceeded. To test the potential of the models we estimated sensitivity, specificity and timeliness on simulated time series and compared the results with an alternative approach of a linear regression model adjusted for trends and season. We also used two observed series for Rubella notifications and Salmonella infections and compared our findings with the expert opinions on these series. The hierarchical time series models approach shows high sensitivity and specificity and correctly identifies outbreaks at an early stage. This, in our opinion, makes the proposed model a reliable tool for adequate automated detection of infectious disease outbreaks.

Algorithms↗

PubMed1996

Interregional foodborne salmonellosis outbreak due to powdered infant formula contaminated with lactose-fermenting Salmonella virchow.

Spain's Salmonella surveillance system backed by regionally-based epidemiologists around the country made it possible to detect and halt the spread of a foodborne salmonellosis outbreak due to powdered infant formula contaminated with a lactose-fermenting strain of Salmonella virchow. Forty-eight cases involving children, mostly under 7 months old, were detected in 14 out of Spain's 17 Regions. The outbreak started in January and ended in June 1994. All cases were microbiologically confirmed. The implicated strain had a 3.6 kb plasmid, was susceptible to all antimicrobials tested except nitrofurantoin and was phagetype 4a. Isolates from 8 of 24 Brand "A" milk samples tested had the same characteristics as case isolates. All affected/suspect batches of Brand "A" milk were destroyed and the product withdrawn from sale, which led to the end of the outbreak. This incident underscores the importance of maintaining surveillance systems able to detect and prevent foodborne outbreaks and alert to the possibility of isolating unusual lactose-fermenting Salmonella serotypes in especially sensitive food products.

Animals↗

PubMed1996

Two outbreaks of typhoid fever related to the war in Bosnia and Herzegovina.

Two outbreaks of typhoid fever caused by Salmonella typhi of the same phagotype (A, biotype II), and antibiotic susceptibility are reported. Both occurred during the war in Bosnia and Herzegovina. The first outbreak appeared among the refugees from the town of Jajce. The second outbreak appeared among the inhabitants in the village of Vidosi near Livno. This report describes main clinical, epidemiological and laboratory findings for 22 patients treated in Split University Hospital, Croatia, in the period November 1992-January 1993. Possible epidemiological connections between those two outbreaks are discussed.

Adolescent↗

PubMed1990

Outbreak of nosocomial infections due to Klebsiella pneumoniae producing SHV-4 beta-lactamase.

One hundred and fifty-four clinical isolates of Klebsiella pneumoniae resistant to broad-spectrum cephalosporins, aztreonam and amikacin were responsible for an outbreak of nosocomial infections lasting eight months in a university hospital in Paris. This outbreak occurred in the intensive care unit (39 patients), haematology units (8 patients) and surgical and medical units (11 patients). Antibiotic resistant strains were isolated from the urinary tract (48%), wound and drainage fluids (21%), respiratory tract (14%), blood (12%) and stools (5%). High resistance to oxyimino-beta-lactams was mediated by a plasmid-encoded beta-lactamase with an isoelectric point of 7.8 (SHV-4). This CAZ-type enzyme conferred a higher level of resistance to ceftazidime and aztreonam (geometric mean MIC 135 mg/l) than to cefotaxime (geometric mean MIC 14 mg/l). All isolates were of the same biotype (weakly urease positive and no sucrose fermentation). Eight Klebsiella pneumoniae strains isolated in different units and at different times of the outbreak were of the same serotype, had common plasmid patterns and harboured a large self-transferable plasmid of about 180 kilobases encoding resistance to penicillins, oxyimino-beta-lactams, aminoglycosides, tetracycline and trimethoprim. These eight large plasmids had indistinguishable EcoRI restriction patterns. These results suggest that a single strain of Klebsiella pneumoniae was responsible for this outbreak.

Anti-Bacterial Agents↗

PubMed1995

Typhoid fever in the park: epidemiology of an outbreak at a cultural interface.

The number of reported outbreaks of typhoid fever in the United States has recently increased. Only six were reported from 1980-1989, but seven outbreaks were reported in 1990. In August 1990, health officials in Montgomery County, Maryland, were notified of two cases of typhoid fever among persons who had attended both a family picnic attended by 60 persons and a Latin Food Festival attended by 100,000 people. We obtained interviews, blood and stool cultures, and Vi serologies from attendees at and food handlers for the picnic. We defined cases as culture-confirmed or probable. Of the 60 picnic attendees, 24 (40%) had cases, of which 16 were culture confirmed. Those who ate potato salad were at increased risk of disease (17/32 vs. 6/28, relative risk [RR] = 2.5, 95% confidence interval [CI] 1.1-5.4). Picnic attendees who also attended the Latin Food Festival were not at significantly greater risk of disease than those who did not, (11/22 vs. 13/38, RR = 1.5, CI = 0.8-2.7) and we found no evidence of disease among other festival attendees. The potato salad was prepared with intensive handling and without adequate temperature control by a recent immigrant from El Salvador who was asymptomatic, did not attend the picnic, had Salmonella typhi (S. typhi) in her stool, and had elevated Vi antibodies, strongly suggestive of the carrier state. Outbreaks of typhoid fever are a threat for cosmopolitan communities. While currently available control measures are unlikely to prevent all outbreaks, thorough investigation can identify previously unrecognized carriers.

Adolescent↗

PubMed1985

Outbreaks of peste des petits ruminants in village goat flocks in Nigeria.

Peste des petits ruminants (PPR) is a major disease constraint of goat production in Nigeria. Investigation of three outbreaks in village goat populations in south-west Nigeria showed overall attack rates of 42.4%, 13.7% and 37.1% and case fatality rates of 86.9%, 41% and 63.9% respectively. Statistically significant differences were observed between attack rates in different age groups in each of the outbreaks. Based on the mortalities suffered the estimated average loss per goat in each of the three outbreaks was N9.15, N1.36 and N5.84 respectively. On the assumption that a goat population is subjected to an outbreak of the disease every five years these estimates would indicate that an annual sum ranging from N1.83 per goat at the highest level of loss and N0.27 per goat at the lowest level of loss could be profitably spent in the successful prevention of the disease.

Animals↗

PubMed2002

Measles outbreak in a Periurban area of Chandigarh: need for improving vaccine coverage and strengthening surveillance.

OBJECTIVE: An outbreak of measles was investigated in the periurban areas of Chandigarh Union Territory, during the months of December 1998 to February 1999. Mainly the children below 15 years of age were affected. The children of migrant labourers belonging to the neighbouring states of Uttar Pradesh and Bihar constituted the majority of population in the area under study. They belonged to lower socio economic status with low immunization coverage. METHODS: A total of 2968 houses were surveyed for epidemiological investigations in the areas of colony No. 5, Ramdarbar, Palsora and Pandit colony of Kajheri, covering a population of 14,601 and 7.3% (216/2968) of families were affected in the outbreak. RESULTS: Two hundred and eighty three cases of measles were reported with an attack rate of 4.5% and male to female ratio of (M:F) 5.3%:3.6%. Among the measles cases, 48.8% had received measles vaccination. The outbreak was investigated by detecting measles specific IgG/IgM antibodies either in acute or convalescent serum samples or both. Due to inadequate surveillance system and containment measures, the outbreak was in full swing during the winter months. Measles related complications were reported in 31.1% cases (i.e. diarrhoea in 15.2% and Pneumonia is 7.1%). CONCLUSION: Following smallpox and guinea worm eradication, WHO's next thrust, is on eradication of poliomyelitis and measles. Hence, strengthening of disease surveillance as well as vaccination policies are mandatory to achieve disease control in these areas.

Adolescent↗

PubMed1978

Studies on the outbreak of hepatitis A in an institute for mentally retarded children.

The authors encountered an outbreak of acute hepatitis in a public institute for mentally retarded children in Aomori Prefecture, Japan. Studies revealed that the probable vehicles of transmission of infection were contaminated water, contaminated meals, and close contact. From the clinical manifestations and epidemiological investigations of 41 affected children and staff members, an outbreak of hepatitis A was strongly suspected. Immune electron microscopy disclosed hepatitis A virus antigen particles in the stool specimens collected during the few days before and after peak transaminase elevation. Hepatitis A antigen was further extracted and purified. The antigen was the first reported recovery of the virus from a natural outbreak of hapatitis A in Asia. Subsequently, with the immune adherence hemagglutination test, using this extracted antigen, an increase in titer of antibody to hepatitis A antigen was demonstrated. Thus, this epidemic was serologically established as an outbreak of hepatitis A. Human immune serum globulin for the protection against hepatitis A was administrated to the 80 individuals concerned, and it was effective in preventing the clinical manifestation of hepatitis.

Adolescent↗

PubMed2004

[Use of information on nosocomial outbreaks for infection control].

Outbreaks of nosocomial infections can be associated with significant morbidity in the patients involved and require time, effort, and resources. In addition, they may lead to panic reactions among health care workers and patients as well as the community. However, their systematic analysis can contribute to knowledge about the sources and transmission of nosocomial infections and the best methods for prevention. Furthermore, the results of outbreak investigations may serve as a valuable tool for education. That is why a systematic register of nosocomial outbreaks would be a very useful instrument for people working in the field of nosocomial infection control. This article describes the need for a systematic collection of outbreaks published in the literature and an available possibility for filling this gap.

Adult↗

PubMed2005

An Austrian outbreak of Salmonella enteritidis phage type 36 in 2004.

In June 2004, an egg packing station was epidemiologically incriminated as possibly distributing the vehicle of the Salmonella enterica subsp. enterica ser. Typhimurium definitive type (DT) U291 outbreak which began in September 2003 and--as of June 2004 affected more than 100 persons all over Austria and 8 German tourists. A total of 68 egg producing farms were screened for salmonella. Whereas all samples tested negative for S. Typhimurium DT U291, one batch of laying hens was identified as being heavily contaminated with a rare Salmonella enterica subsp. enterica ser. Enteritidis phage type, namely PT 36. This phage type was cultured from 6 of 7 swabs from pooled fecal samples (drag swabs), from 1 of 4 samples of pooled yolks, and from 7 of 11 hens tested (ovaries, liver and intestinal content pooled per hen). In 2004, a total of 36 culture-confirmed human PT 36 infections (19 manifest cases, 12 asymptomatic carriers, and 5 excreters with unknown clinical status) were documented in 4 of the 9 Austrian provinces. It was possible to demonstrate that eggs from this single farm were the probable source of infection for 30 of 31 culture-confirmed human infections. Only in the case of one patient, who regularly purchased eggs at the local market, could no connection to the farm be proven due to inability to trace the market's egg source. The PT 36 outbreak ceased after elimination of the contaminated flock. This episode underlines the considerable potential of adequate epidemiological and microbiological investigations of food-borne outbreaks to improve prevention and control of communicable diseases. The source of the S. Typhimurium DT U291 outbreak--which initially prompted this investigation--is still not identified and accounts for more than 300 human cases until August 2005.

Animals↗

PubMed2005

Genetic characterization of H5N1 avian influenza viruses isolated in southern China during the 2003-04 avian influenza outbreaks.

The recent H5N1 avian influenza outbreaks in Asia spread over more than 8 countries. It has caused enormous economic loss and grand challenges for the public health. During these breakouts we isolated three strains of H5N1 Avian Influenza Virus (AIV) from chickens and one from duck in different farms of Southern China. We completely sequenced these four AIVs. Molecular characterization demonstrated that these strains retain the reported H5N1 AIV sequence properties relevant to virus virulence and host adaptation. Phylogeny results demonstrated that three of these isolates (except A/Chicken/Guangdong/174/04) were closely linked to other H5N1 AIVs isolated from the recent H5N1 outbreaks in Asia. Six of 8 segments (except PA and M) of A/Chicken/Guangdong/174/04 also shares a close linkage to other H5N1 AIVs isolated from the recent H5N1 outbreaks. However, the PA gene of A/Chicken/Guangdong/174/04 and another H5N1 strain forms a distinct subgroup along with an H6N1 AIV, and the M gene of A/Chicken/Guangdong/174/04 shows a close linkage to some H5N1 AIVs from aquatic species in China. Our findings suggest that a new genotype of AIV (in addition to previous reported ones) was present during the 2003-04 Asian bird flu outbreaks and that continuing virus surveillance of AIVs be conducted to monitor the evolutionary paths of the A/Chicken/Guangdong/174/04-like AIVs.

Animals↗

PubMed2002

Retrospective analysis of the first clonal outbreak of nalidixic acid-resistant Shigella sonnei shigellosis in Israel.

Reported here is a retrospective molecular analysis of the isolates recovered from the first outbreak of nalidixic acid (NA)-resistant Shigella sonnei shigellosis to occur in Israel. The outbreak affected 94 children. In the retrospective analysis, a total of 13 NA-resistant isolates and five NA-susceptible isolates recovered during the outbreak period were examined. Restriction fragment length polymorphism profiles obtained by digestion with BamHI, PvuI, HinfI or SmaI yielded identical profiles for all 18 isolates. All NA-resistant strains had an identical plasmid profile, but this profile differed from that displayed by the susceptible strains. In all of the NA-resistant strains a 304 bp fragment in the gyrA gene coding for a region associated with NA resistance was sequenced and showed a single point mutation, Ser83-->Phe. In this outbreak, the isolates of NA-resistant Shigella sonnei belonged to a single clone and NA resistance was associated with a point mutation in the gyrA gene.

Adolescent↗

PubMed2000

Long-term outcome of acute hepatitis B and C in an outbreak of hepatitis in 1969-72.

The objective of this study was to investigate the epidemiology, etiology, and long-term outcome of an extended outbreak of acute hepatitis that occurred in an area of Sweden between 1969 and 1972. The outbreak was analyzed retrospectively by retesting stored frozen serum samples for the presence of hepatitis A, B and C markers. The results were compared with the diagnoses that had been determined during the outbreak. Of 180 patients, 29 (16%) had acute hepatitis A, 126 (70%) had acute hepatitis B, and eight (4.4%) had acute hepatitis C. The Australia antigen test used during the outbreak had failed to identify 21 patients with acute hepatitis B virus infection. Genotyping of the hepatitis B virus strains showed that genotype D was the most prevalent, irrespective of the transmission route. An attempt was made to follow up patients with unresolved hepatitis B virus infection, 25-27 years after the acute infection. None of the 100 patients with acute hepatitis B infection who were traced had become chronic carriers. In ten patients with hepatitis C virus infection, the follow-up showed considerable variation in the outcome, ranging from spontaneous resolution to death through liver cirrhosis. Intravenous drug users had a high prevalence of hepatitis C virus infection, with 52% testing positive for hepatitis C antibodies.

Acute Disease↗

PubMed1988

Community outbreak of thyrotoxicosis: epidemiology, immunogenetic characteristics, and long-term outcome.

Between January and March 1984, the first community outbreak of transient thyrotoxicosis in the United States was documented in a seven-county area of southeastern Nebraska; 36 of the total 49 patients resided in York County (2.4 cases per 1,000 population). The median age of patients was 36 years, range six to 82 years; 51 percent were women. By definition, all patients were symptomatic, visited a physician, and had a newly identified elevated serum concentration of thyroxine or triiodothyronine of unknown cause. None had a goiter or a painful thyroid gland. Low 131I uptake measurements were found in all nine patients studied. Six patients were hospitalized; none died. Investigation of all 12 household contacts of eight selected patients revealed five additional persons with thyrotoxicosis and four with asymptomatic hyperthyroxinemia. A case-control study revealed that illness was associated with a significantly higher frequency of a reported recent respiratory viral-like condition. In another case-control study, the HLA-DR3 antigen was present in more case subjects (39 percent) than control subjects (14 percent). In addition, a significantly higher proportion of patients than control subjects purchased beef from one of the three supermarkets in York Country. Concomitant with the outbreak, the supermarket implicated in the outbreak purchased an unusually large quantity of beef (7,000 pounds) from a nonregular supplier in Nebraska, which had reportedly instituted the practice of trimming gullets (a procedure that removes the muscles from bovine larynx for beef) about three months earlier. Thus, it is concluded that the Nebraska outbreak, like one in Minnesota that occurred 18 months later, probably resulted from patients having eaten ground beef that was contaminated with bovine thyroid gland. This form of thyrotoxicosis, perhaps misdiagnosed as painless thyroiditis in the past, probably represents a previously under-recognized public health problem.

Adult↗

PubMed1993

Underutilization of pneumococcal vaccine in nursing home in Washington State: report of a serotype-specific outbreak and a survey.

PURPOSE: To describe an outbreak of pneumococcal disease in a Washington state nursing home and to report a survey of pneumococcal vaccine utilization in Washington nursing homes. PATIENTS AND METHODS: Outbreak. Data were collected from nursing home residents' records. Nasopharyngeal cultures were obtained from residents and staff. Survey. Fifty-four randomly selected Washington nursing homes were surveyed about pneumococcal vaccine utilization and policies. RESULTS: Outbreak. Three confirmed and 4 possible cases of pneumococcal disease occurred over 9 days among 94 residents; 5 patients (71%) died. Cases were identified among 6 of 42 residents on 1 wing, compared with 1 of 52 on the other 2 wings (relative risk 7.4, 95% confidence interval 1.0, 398.5). Streptococcus pneumoniae serotype 9V was cultured from the blood of 3 confirmed case-patients and the nasopharynx of 2 of 73 residents. Only 7% of residents had received pneumococcal vaccine, including one case-patient who had received 14-valent vaccine without serotype 9V. Survey. Only 22% of residents were reported to have received pneumococcal vaccine; vaccination status was unknown for 66%. Physician discretion determined pneumococcal vaccination in 49 (91%) nursing homes; 9 (17%) had a written policy. Two major barriers to pneumococcal vaccination were cited: low priority among physicians (43%) and difficulty in determining residents' vaccine history (37%). CONCLUSIONS: A pneumococcal disease outbreak among undervaccinated nursing home residents probably resulted from person-to-person transmission. Pneumococcal vaccine appears to be underutilized in Washington state nursing homes.

Aged↗

PubMed1991

Outbreak of paralytic poliomyelitis in Oman: evidence for widespread transmission among fully vaccinated children.

From January, 1988, to March, 1989, a widespread outbreak (118 cases) of poliomyelitis type 1 occurred in Oman. Incidence of paralytic disease was highest in children younger than 2 years (87/100,000) despite an immunisation programme that recently had raised coverage with 3 doses of oral poliovirus vaccine (OPV) among 12-month-old children from 67% to 87%. We did a case-control study (70 case-patients, 692 age-matched controls) to estimate the clinical efficacy of OPV, assessed the immunogenicity of OPV and extent of poliovirus spread by serology, retrospectively evaluated the cold chain and vaccine potency, and sought the origin of the outbreak strain by genomic sequencing. 3 doses of OPV reduced the risk of paralysis by 91%; vaccine failures could not be explained by failures in the cold chain nor on suboptimum vaccine potency. Cases and controls had virtually identical type 1 neutralising antibody profiles, suggesting that poliovirus type 1 circulation was widespread. Genomic sequencing indicated that the outbreak strain had been recently imported from South Asia and was distinguishable from isolates indigenous to the Middle East. Accumulation of enough children to sustain the outbreak seems to have been due to previous success of the immunisation programme in reducing spread of endemic strains, suboptimum efficacy of OPV, and delay in completing the primary immunisation series until 7 months of age. Additionally, the estimated attack rate of infection among children aged 9-23 months exceeded 25% in some regions, suggesting that a substantial proportion of fully vaccinated children had been involved in the chain of transmission.

Case-Control Studies↗