An outbreak of food-borne enterotoxigenic Escherichia coli diarrhoea in England

An outbreak of diarrhoea with abdominal pain occurred among members of the staff of a school and their guests after a social function at which a cold buffet was served. Sixty people attended the function and 43 subsequently completed questionnaires. Of these, 27 had diarrhoea. The median incubation period was 36 h and the range 12-66 h. Food history analysis showed an association between diarrhoea and eating curried turkey mayonnaise. Stool specimens from 13 of those who developed diarrhoea were examined: Escherichia coli 06.H16 (producing heat-stable and heat-labile enterotoxins) was found in nine specimens and E. coli 027.H20 (producing heat-stable enterotoxin) in 11 specimens. Eight patients had both strains and only one was negative for enterotoxigenic E. coli. Food samples were not available for examination. Enterotoxigenic E. coli should be considered as a possible cause in well-defined outbreaks of food-borne diarrhoea with abdominal pain.     

Clinical study of an outbreak of aseptic meningitis due to echovirus type 30 in Munakata City in 1997-1998

From October, 1997 through July, 1998, an outbreak of aseptic meningitis due to echovirus type 30 occurred in the northern part of Kyushu area in Japan. In this outbreak, clinical and virologic observations were carried out on 157 in-patients with aseptic meningitis at our hospital. The age of the patients ranged from 1 year and 9 months to 57-year old. One hundred and twenty out of 157 cases were the children under 15 years of age, and in this age group, male/female ratio was 2:1. The largest proportion of cases occurred in the 5- to 9-year age group. The number of cases reached a peak in December, 1997, but the epidemic extended to the next summer. In 12 families, more than one person became ill (total 22 cases). Virus isolation from cerebrospinal fluid (CSF) was tried on 130 out of 157 cases. Echovirus 30 was isolated in 74 cases (58 children, 16 adults), and echovirus 18 in 9 cases from June, 1998 until the end of the study. Paired acute and convalescent sera were available from the 25 patients with negative virus isolation, and 7 out of 25 patients had a fourfold or greater rise in neutralizing antibodies. Headache, fever, vomiting, nuchal rigidity were detectable in most cases, but in this outbreak, continued severe headache was characteristic. Eye pain was experienced by 2% of the total cases. In children, gastrointestinal symptoms were noted in 12% of the cases, but were not in adult patients. The CSF cell counts ranged from 2 to 3,478 cells per cubic millimeter. Fifty-eight percent were predominantly lymphocytic, while 42% were polymorphonuclear predominant. Virus was highly isolated from the CSF when the specimens were obtained within three days after the onset of the acute illness, but in one case, virus was isolated on day 7. In a few cases, virus was isolated without pleocytosis in CSF.     

An Outbreak of Shiga Toxin-Producing Escherichia coli O104:H4 Hemolytic Uremic Syndrome in Germany: Presentation and Short-term Outcome in Children

Background.?In May and June 2011 the largest known outbreak of hemolytic uremic syndrome (HUS) occurred in northern Germany. Because, quite unusually, a large number of adults was affected and the causative Escherichia coli strain, serotype O104:H4, showed an atypical virulence factor pattern, it was speculated that this outbreak was associated with an aggressive course and an unfavorable prognosis also in children. Methods.?Retrospective analysis of medical records of 90 children and comparison to previous outbreak and sporadic case series. Results.?Median age was unusually high (11.5 years) compared with that in historical series. Only 1 patient (1.1%) died in the acute phase. Most patients (67/90 [74%]) received supportive care only. Renal replacement therapy was required in 64 of 90 (71%) of the children. Neurological complications, mainly seizures and altered mental stage, were present in 23 of 90 (26%) patients. Ten patients received plasmapheresis, 6 eculizumab, and 7 a combination of both. After a median follow-up of 4 months, renal function normalized in 85 of 90 (94%) patients, whereas 3 patients had chronic kidney disease stage 3 or 4, and 1 patient (1.1%) still requires dialysis. Complete neurological recovery occurred in 18 of 23 patients. Mild to moderate and major residual neurological changes were present in 3 patients and 1 patient, respectively, although all patients were still improving. Conclusions.?E. coli O104:H4 caused the largest HUS outbreak in children reported in detail to date and most patients received supportive treatment only. Initial morbidity, as well as short-term outcome, due to this pathogen, is comparable to previous pediatric series of Shiga toxin-producing E. coli HUS.     

一起由产气荚膜梭菌和肠聚集性大肠埃希菌共感染导致的聚集性腹泻事件病原学分析

目的 对一起产气荚膜梭菌和肠聚集性大肠埃希菌(PFGE)混合感染导致的腹泻暴发事件进行病原学分析.方法 采集暴发事件的病例粪便样本;病原体筛查使用实时荧光PCR方法;细菌分离使用培养法;菌株毒力基因鉴定使用普通PCR方法;菌株抗生素敏感性测试使用微量内汤稀释法,菌株分子分型使用脉冲场凝胶电泳方法.结果 9份粪便样本核酸...     

Adherence of bacteria to the intestine in sporadic cases of enteropathogenic Escherichia coli-associated diarrhea in infants and young children: a prospective study

Intimate adherence of bacteria to duodenal enterocytes was demonstrated in a 12-mo-old child with sporadic diarrhea that was associated with an enteropathogenic Escherichia coli (EPEC) of the serogroup O111:K58. Therefore, a prospective study was initiated to determine if identification of EPEC in stools from sporadic cases of diarrhea of longer than 10 days in duration in children under 24 mo of age correlated with E. coli colonization of the proximal small intestine and with binding of bacteria to intestinal epithelial cells. Colonization was determined by culture of duodenal aspirates and enteroadherence by light- and electron-microscopic evaluation of both duodenal and rectal mucosa. Each EPEC isolate was examined for several previously proposed laboratory markers of virulence including alpha-hemolysin production, agglutination of erythrocytes, cell surface hydrophobicity properties, adherence to HEp-2 cells, and Verotoxin production. Ten sporadic cases of EPEC-associated diarrhea, severe enough to require hospitalization in each instance, were present among 105 patients in whom EPEC were identified in stools. Of the 10 cases, 9 were evaluated in more detail. In contrast to the first case, in the prospective study E. coli were cultured from duodenal aspirates in only 1 patient and enteroadherent organisms were not present on careful review of small bowel (0/9) and rectal (0/7) mucosa. Hemolysin production (9 of 10 EPEC strains), mannose-sensitive hemagglutination (7/10), hydrophobic cell surface properties (0/10), adherence to HEp-2 cells (7/10), and production of Verotoxin (0/10) did not distinguish the one enteroadherent EPEC from the nine EPEC strains in which in vivo enteroadherence was not documented. In this study of sporadic cases of EPEC-associated diarrhea in young children, bacterial colonization of the small bowel and enteroadherence in vivo could not routinely be demonstrated. In addition, those laboratory assays of bacterial virulence that were evaluated did not distinguish the adherent strain from nonadherent EPEC strains.     

Serum anti-lPS antibody production in an outbreak of enterohemorrhagic Escherichia coli O157 infection among schoolchildren

Although there have been many reports of the usefulness of serodiagnosis of enterohemorrhagic Escherichia coli (EHEC) O157, the serotype of the bacteria detected and the increase in anti-LPS antibody have not always been consistent. In this study we investigated the diagnostic significance of measurements of anti-LPS antibody by ELISA in an outbreak of O157 infection among schoolchildren in whom the bacteriological test findings were clarified and the age groups were uniform. The anti-LPS antibody titer was measured in 31 patients (77 serum samples) in an outbreak of EHEC O157 : H7 infection (220 children infected) that occurred in a primary school in Morioka in 1996. The anti-O157 LPS antibody positivity rates of IgM, IgG, and IgA were 98.7%, 85.7%, and 98.7%, respectively. Between the time the meal that caused the outbreak and 19 days later, anti-O157 LPS IgM antibody and IgA antibody were detected in all patients. The specificity was investigated using control serum, and the specificity of IgM, IgG, and IgA was 93.5%, 93.5%, and 97.2%, respectively. Some samples contained antibodies against O111 and O26 LPS, but the titers were lower than the anti-O157 antibody titer. The anti-O111 antibody titer and anti-O26 antibody titer were highly correlated, suggesting that they were crossreactive antibodies for O157 LPS. No significant correlation was found between differences in clinical manifestations and the anti-O157 LPS antibody titer in this O157 outbreak in schoolchildren. It was clarified that an increase in anti-LPS antibody was found to support the diagnosis of mild cases of 0157 infection infection as well as severe cases.     

A multistate outbreak of Escherichia coli O157:H7 infections associated with consumption of mesclun lettuce.

BACKGROUND: An outbreak of Escherichia coli O157:H7 infections in Connecticut and Illinois during May 28 to June 27, 1996, was investigated to determine the source of infections. METHODS: Independent case-control studies were performed in both states. Pulsed-field gel electrophoresis (PFGE) was performed on E. coli O157:H7 isolates. A case-patient was defined as a Connecticut or northern Illinois resident with diarrhea whose stool culture yielded E. coli O157:H7 of the outbreak-associated PFGE subtype. Controls were town-, age-, and sex-matched to case-patients. We traced implicated lettuce to the farm level and performed environmental investigations to identify unsafe lettuce production practices. RESULTS: In Connecticut and Illinois, infection was associated with consumption of mesclun lettuce (Connecticut matched odds ratio [MOR], undefined; 95% confidence interval [CI], 3.4 to infinity; and Illinois MOR, undefined; 95% CI, 1.4 to infinity). We traced implicated lettuce to a single grower-processor. Cattle, a known E. coli O157:H7 reservoir, were found near the lettuce fields. Escherichia coli (an indicator of fecal contamination) was cultured from wash water and finished lettuce. A trace-forward investigation identified 3 additional states that received implicated lettuce; E. coli O157:H7 isolates from patients in 1 of these states matched the outbreak-associated PFGE subtype. CONCLUSIONS: This multistate outbreak of E. coli O157:H7 infections was associated with consumption of mesclun lettuce from a single producer. Molecular subtyping facilitated the epidemiological investigation. This investigation increased the knowledge about current production practices that may contribute to the contamination of lettuce by microbial pathogens. Lettuce production practices should be monitored for microbiological safety.     

Association of patterns of Escherichia coli adherence to HEp-2 cells with acute and persistent diarrhea]

In Brazil diarrhea is the cause of approximately 15% of death among infants. Enteropathogenic E coli is the most important bacterial agent causing acute diarrhea, which is defined as less than 14 days of duration. About 30% of these cases may evolve to persistent diarrhea, defined as lasting more than 14 days. In this work it was carried out a case-control study including 34 children under 2 years of age, and admitted to hospital facilities in S?o Paulo for rehydration therapy. Thirty-four age matched children hospitalized in the same facilities, and presenting no gastrointestinal symptoms were included as controls. Stool samples were analyzed for the presence of bacterial pathogens (diarrheagenic E coli, Shigella, Salmonella, Yersinia, and Campylobacter), protoparasytes, rotavirus, and enteric adenovirus. The E coli strains isolated were analyzed for their ability to adhere to HEp-2 cultured cells, in a 3 h adhesion assay. Search for homology with DNA probes for localized adherence (EAF, eaeA probes), AA (enteroagregative adherence) (AA probe), and diffuse adherence (F1845, AIDA-I probes) was carried out by the colony hybridization method. Twenty-four of the cases were acute diarrhea and 10 persistent diarrhea. Strains with localized adherence were associated with acute and persistent diarrhea. About 23.5% of E coli were associated with typical Enteropathogenic E coli strains (EAF+, eaeA+). Enteroaggregative E coli (EAggEC) (AA+) was isolated only from cases and in similar frequency for acute and persistent diarrhea. Diffusely adherent E coli (DAEC) which did not hybridize with the diffuse adherence probes were isolated among cases and controls. E coli eaeA+ with localized-like adherence was isolated from cases in a frequency three times higher than in controls, suggesting that it may really have a pathogenic potential.     

A waterborne outbreak in Missouri of Escherichia coli O157:H7 associated with bloody diarrhea and death.

OBJECTIVE: To describe and determine the source of a large outbreak of Escherichia coli O157:H7 (ECO157) infections in Missouri. DESIGN: A case-control study and a household survey. SETTING: A small city in a rural Missouri township that had an unchlorinated water supply. PATIENTS: Case patients were residents of or visitors to Burdine Township with bloody diarrhea or diarrhea and abdominal cramps occurring between 15 December 1989 and 20 January 1990. MEASUREMENTS: Escherichia coli O157 was isolated from 21 stool specimens. All isolates were resistant to sulfisoxazole, tetracycline, and streptomycin; produced Shiga-like toxins I and II; and had one 60-megadalton plasmid. RESULTS: Among the 243 case patients, 86 had bloody stools, 32 were hospitalized, 4 died, and 2 had the hemolytic uremic syndrome. In the case-control study, no food was associated with illness, but ill persons had drunk more municipal water than had controls (P = 0.04). The survey showed that, during the peak of the outbreak, bloody diarrhea was 18.2 times more likely to occur in persons living inside the city and using municipal water than in persons living outside the city and using private well water (P = 0.001). Shortly before the peak of the outbreak, 45 water meters were replaced, and two water mains ruptured. The number of new cases declined rapidly after residents were ordered to boil water and after chlorination of the water supply. CONCLUSIONS: This was the largest outbreak of ECO157 infections, the first due to a multiply resistant organism, and the first shown to be transmitted by water. System-wide chlorination as well as hyperchlorination during repairs might have prevented this outbreak. Both bloody and nonbloody diarrhea may be common manifestations of this infection, which is probably underdiagnosed because of the failure of routine stool cultures to identify the organism. Cities with deteriorating water systems using untreated water risk widespread illness from contaminated drinking water.     

Chlamydia pneumoniae infections in Norway 1981-87 earlier diagnosed as ornithosis

Ornithosis has been a notifiable disease in Norway since 1957. During an outbreak of respiratory disease in 1981-82, described as ornithosis, contact with birds was stated in only 50% of the cases, suggesting that the infection was spread by interhuman transmission. A similar outbreak occurred in the western part of Norway in 1987. Serum specimens from altogether 260 patients, collected during the outbreaks in 1981-82 and in 1987, were investigated for antibodies against Chlamydia pneumoniae (strain TWAR). Evidence of recent infection with C. pneumoniae was found in 67.7% of the cases. The results indicate that the increased incidence of ornithosis in 1981-82 and in 1987 was due mainly to C. pneumoniae infections.     

Effects of adherence factors and human bile on bacterial attachment and biliary stent blockage: an in vitro study

BACKGROUND: Bacterial attachment plays an important role in the initiation of biliary sludge formation and stent blockage. In vitro studies were conducted to determine the effects of adherence factors, namely pili and glycocalyx production, and culture media, including brain heart infusion broth, modified Vogel and Bonner medium, and human bile, on the adherence of Escherichia coli to plastic stents. METHODS: Clinical isolates of E coli with different adherence mechanisms, that is, piliated (P+) or nonpiliated (P-), glycocalyx producing (G+) and nonglycocalyx producing (G-), were obtained from clogged stents. Adherence studies were conducted by using the modified Robbins device, and stents were removed at regular intervals to determine the number of attached bacteria/cm(2) with the viable plate count method. Polyethylene stents were used to compare the adherence curves of E coli with different adherence factors in brain heart infusion broth. The effects of different culture media on the adherence of P+G+ E coli to polyethylene stents were determined. In addition, the adherence of P+G+ E coli to different plastics in brain heart infusion broth and human bile was compared. RESULTS: P+G+ E coli adhered better than P-G+ and P-G- E coli to polyethylene stents. Modified Vogel and Bonner medium, which stimulates glycocalyx production, enhanced the attachment of P+G+ E coli, whereas human bile decreased E coli attachment to polyethylene stents, despite an increase in glycocalyx production. There was a difference in adherence of P+G+ E coli to polyethylene, polyurethane, and Teflon stents in brain heart infusion broth, but the differences were nullified in the presence of human bile. CONCLUSIONS: P+G+ E coli with both adherence factors adhere best to plastic stents. Media such as modified Vogel and Bonner medium that stimulate glycocalyx production also enhance bacterial attachment. The toxic effects of bile salts in human bile on the bacteria might alter the adherence mechanism and reduce E coli attachment.     

A diffuse outbreak of enterohemorrhagic Escherichia coli O157:H7 related to the Japanese-style pickles in Saitama,Japan

We have experienced an outbreak of enterohemorrhagic E. coli O157:H7 (Shiga-like toxin 1 & 2 producing) in child independence support facilities in the all dormitory system, in Saitama August 2001. There were 13 patient and EHEC O157s were detected in a total of 29 specimens. As a result of epidemic inspection and microbiological investigation. We recognized that the causative food was Japanese-style pickles named "Wafu-Kimuchi" which had been sold in Saitama and Tokyo area. As the same period, several infections caused by EHEC O157 were considered the same origin in Saitama (8 patients in 5 families). Furthermore some infections happened also in Tokyo. It was made clear this outbreak was a part of a diffuse outbreak caused by Wafu-Kimuchi. In diffuse outbreaks, it is important to grasp a common feature of the individual cases in a wide area. The exchange of epidemic information between two or more municipalities and the guess of the identity in the DNA levels of strains were the key role to the elucidation of this case.     

Community outbreak of Mycoplasma pneumoniae infection: school-based cluster of neurologic disease associated with household transmission of respiratory illness

BACKGROUND: We investigated an outbreak of severe neurologic disease and pneumonia that occurred among students at 4 schools in Rhode Island. METHODS: We identified cases of encephalitis, encephalomyelitis, and pneumonia that occurred among schoolchildren from 1 September 2006 through 9 February 2007, and we performed serologic tests, polymerase chain reaction (PCR) analysis, and culture for the detection of multiple pathogens in oropharyngeal and nasopharyngeal specimens. Students with positive results of M. pneumoniae IgM serologic testing and no alternative diagnosis were considered to be infected with M. pneumoniae. At school A, we used questionnaires to identify students and their household contacts who made visits to physicians for pneumonia and cough. We compared observed and expected rates of pneumonia. RESULTS: Rates of pneumonia among elementary students (122 cases/1000 student-years) were > 5-fold higher than expected. Three students had encephalitis or encephalomyelitis, and 76 had pneumonia. Of these 2 groups of students, 2 (66%) and 57 students (75%), respectively, had M. pneumoniae infection. M. pneumoniae was detected by PCR in 10 students with pneumonia; 5 of these specimens were cultured, and M. pneumoniae was isolated in 4. Of 202 households of students attending school A, 20 (10%) accounted for 61% of visits to physicians for pneumonia or cough. Of 19 household contacts of students with pneumonia, 8 (42%) developed pneumonia and 6 (32%) reported visits for cough. CONCLUSIONS: M. pneumoniae caused a community-wide outbreak of cough illness and pneumonia and was associated with the development of life-threatening neurologic disease. Although M. pneumoniae was detected in schools, its transmission in households amplified the outbreak. Interrupting household transmission should be a priority during future outbreaks.     

Severe manifestation of acute hepatitis A recently found in Gunma,Japan

Background: Background: The incidence of acute hepatitis A infection in Japan peaked 10 years ago and has been decreasing since then. However, an increase in severe cases of the disease has been documented recently. We experienced an outbreak in 1998–1999, and compared the clinical features of the disease in 1998–1999 (recent outbreak) and in 1987–1988 (past outbreak) in our prefecture (Gunma). Methods: Forty patients with acute hepatitis A were admitted to nine Gunma hospitals from October 1998 to September 1999. Their clinical features were compared with those of 100 patients with acute hepatitis A admitted to the same hospitals in 1987–1988. Results: Both outbreaks occurred mostly during the winter-spring season. Secondary familial infection was significantly decreased in the recent outbreak. Patients in the recent outbreak were 7 years older than those in the past outbreak. Laboratory findings, such as serum aspartatate aminotransferase (AST) and alanine aminotransferase (ALT) levels and prothrombin time, were worse in the recent than in the past outbreak. Severe-type hepatitis and fulminant hepatitis occurred in 5 patients (12.5%) in the recent outbreak but in only 2 patients (2.0%) in the past outbreak. Conclusions: Clinical data and manifestations were more severe in the recent outbreak than in the past outbreak of acute hepatitis A. It is important to be aware of hepatitis A virus infection and to take into account the available vaccination against hepatitis A virus in Japan. Received: June 8, 2001 / Accepted: December 27, 2001     

Treatment adherence of 717 patients with tuberculosis in a social security system hospital in Istanbul, Turkey.

SETTING: Tuberculosis clinic in a teaching hospital run by the social security system, Istanbul, Turkey. OBJECTIVE: To determine risk factors associated with treatment adherence. DESIGN: Seven hundred and seventeen patients who commenced treatment for tuberculosis in our clinic from May 1991 to May 1997 were evaluated retrospectively with respect to treatment adherence. Factors with an effect on treatment adherence were investigated. RESULTS: Sputum conversion was achieved in 88.9% of the cases within the first 2 months of treatment. Seven patients died during treatment; of the 710 patients remaining, 106 (14.9%) were non-adherent. This rate decreased from 34.4% in 1991 to 2.0% in 1997. In multi-variate logistic regression analysis, only previous treatment history for tuberculosis was related to non-adherence; treatment adherence rate in new cases was 88.9%, while it was 66.7% in previously treated cases (P < 0.001). CONCLUSION: In new cases, a treatment adherence rate of 88.9% can be considered satisfactory. However, in previously treated cases, an adherence rate of 66.4% must be considered unsatisfactory. Previously treated cases in particular should therefore receive directly observed treatment.     

The return of Cyclospora in 1997: another outbreak of cyclosporiasis in North America associated with imported raspberries. Cyclospora Working Group

BACKGROUND: In the spring of 1996, an outbreak of cyclosporiasis associated with fresh Guatemalan raspberries occurred in the United States and Canada. Another multistate outbreak of cyclosporiasis occurred in North America in the spring of 1997. OBJECTIVE: To identify the vehicle of the outbreak that occurred in the spring of 1997. DESIGN: Retrospective cohort studies of clusters of cases associated with events (such as banquets) and traceback investigations of sources of implicated produce. SETTING: United States and Canada. PATIENTS: Persons who attended events associated with clusters of cases of cyclosporiasis. MEASUREMENTS: Identification of clinically defined or laboratory-confirmed cases of cyclosporiasis and risk factors for infection. RESULTS: 41 clusters of cases were reported in association with events held from 1 April through 26 May in 13 U.S. states, the District of Columbia, and 1 Canadian province. The clusters comprised 762 cases of cyclosporiasis, 192 (25.2%) of which were laboratory confirmed. In addition, 250 laboratory-confirmed sporadic cases were reported in persons who developed gastrointestinal symptoms from April through 15 June, for a total of 1012 cases. Fresh raspberries were the only food common to all 41 events and were the only type of berry served at 9 events (22.0%). Statistically significant associations between consumption of raspberry-containing items and cyclosporiasis were documented for 15 events (40.5% of 37). For 31 of the 33 events with well-documented traceback data, the raspberries either definitely came from Guatemala (8 events) or could have come from Guatemala (23 events). The mode of contamination of the raspberries remains unknown. The outbreak ended shortly after the exportation of fresh raspberries from Guatemala was voluntarily suspended at the end of May 1997. CONCLUSIONS: Similar multistate, multicluster outbreaks of cyclosporiasis associated with consumption of Guatemalan raspberries have occurred in consecutive years. These outbreaks highlight the need for better understanding of the biology and epidemiology of Cyclospora cayetanensis and for stronger prevention and control measures to ensure the safety of produce eaten raw.     

An outbreak of Legionella micdadei pneumonia in transplant patients: evaluation, molecular epidemiology, and control

PURPOSE: To describe a nosocomial outbreak of Legionella micdadei pneumonia in transplant patients and to characterize the source of the outbreak and the control measures utilized. SUBJECTS AND METHODS: We performed retrospective Legionella micdadei serologic testing to enhance case finding in transplant patients with pneumonia that lacked a documented microbial etiology, as well as prospective environmental surveillance of water sites and testing for Legionella in clinical specimens. RESULTS: During a 3-month period, 12 cases of Legionella micdadei pneumonia were identified either by culture or serologic testing among 38 renal and cardiac transplant patients. Legionella micdadei isolates from hot water sources were found by pulsed-field gel electrophoresis to have a DNA banding pattern that was identical to the isolates from the first 3 culture-positive cases and from 2 cases that occurred 16 months later. CONCLUSIONS: Hospitals caring for organ transplant recipients and other immunosuppressed patients must be aware of the possibility of environmental sources of outbreaks of Legionella infection. A first-line screen with the Legionella urine antigen test will identify Legionella pneumophila serogroup 1. However, specific cultures in outbreak situations should be considered to identify other Legionella pneumophila serotypes and the nonpneumophila Legionella species.     

Studies on dengue and dengue haemorrhagic fever (DHF) in West Bengal State, India

A large outbreak of dengue and dengue haemorrhagic fever (DHF) occurred from August to November 2005 involving all districts of West Bengal. Altogether 6293 persons were serologically diagnosed to be suffering from dengue through detection of IgM antibodies, with 27 (0.42%) seropositive deaths. In Kolkata alone 3967 persons were affected with 14 deaths. A total of 874 sera samples from febrile patients were quantitatively analysed for IgG and IgM antibodies using the IVD microwell ELISA dengue fever test kit. In 21.6%, no antibody was detected and 52.6% had only IgG antibodies. In 8.9% only IgM antibodies and in 16.8% both IgG, IgM antibodies were present, suggesting primary and secondary dengue respectively. About 10% of secondary dengue would develop DHF. As in this outbreak secondary dengue was 65.3% of total dengue cases, so of the 6293 dengue victims presumably, 3998 had secondary dengue, thus having risk of DHF in about 400 persons. Case fatality rate amongst DHF patients was 8.5%. This study also indicated that DHF would be a nagging problem in coming days. Age-group analysis of primary and secondary dengue cases revealed that although secondary cases occurred in all ages, more of primary cases belonged to younger ages (1-10) years and more of secondary cases in middle to older ages. Prevailing type during this outbreak was DEN3. This epidemiological study of an outbreak categorized prevalence of primary and secondary dengue, calculated risk factors for precipitation of DHF, model of which could be utilized to compare and evaluate future epidemiological pattern, where-ever and whenever applicable.