In Galicia, Spain, a dramatic increase in the incidence of meningococcal disease was seen in the 1995–6. The annual incidence rose to 11 per 105 inhabitants, and 80% of identified strains were C[ratio ]2b[ratio ]P1.2,5. This led to the implementation of an intensive A+C vaccination campaign for the population aged 18 months to 19 years. During this campaign the prevalence of carriage in areas with high and low incidence was studied. Nasopharyngeal swabs were taken from 9796 subjects immediately before the administration of meningococcal vaccine, plated onto Thayer–Martin plates, incubated and sent for analysis to the Reference Laboratory for Neisseria in Spain. The prevalence of the C[ratio ]2b[ratio ]P1.2,5 strains was 0·6% (95% CI 0·29–0·88) in the high incidence area, and 0·41% (95% CI 0·00–1·04) in the low incidence area, and that of serogroup C (all strains) 1·36% (95% CI 0·80–1·80) and 0·89% (95% CI 0·09–1·69) respectively. The prevalence of N. meningitidis (all strains) was almost the same in both areas (8%). Carriers of the epidemic strain were not found in the 2–4 year age group, that most affected by the disease.

Our data showed a wide distribution but a low carriage rate of the epidemic strain C[ratio ]2b[ratio ]P1.2,5 in the high and low disease incidence areas studied; the difference in the carriage rates between the two areas was not statistically significant.

A stochastic epidemic model was applied to meningococcal disease outbreaks in defined small populations such as military garrisons and schools. Meningococci are spread primarily by asymptomatic carriers and only a small proportion of those infected develop invasive disease. Bayesian predictions of numbers of invasive cases were developed, based on observed data using a stochastic epidemic model. We used additional data sets to model both disease probability and duration of carriage. Markov chain Monte Carlo sampling techniques were used to compute the full posterior distribution which summarized all information drawn together from multiple sources.

A new sulphonamide resistant (SR) C[ratio ]15[ratio ]P1.7,16 meningococcal strain, a variant of the ET-5 clone, dominated in an outbreak of 22 cases in western Norway commencing in 1995. The first eight patients were 15–21 years old from the Nordhordland area, initiating a carrier study in the local high schools. Carriage of SR serogroup C meningococci was detected by routine methods and treated with a single dose of ofloxacin 400 mg. Of 20 treated carriers, 14 harboured the outbreak strain C[ratio ]15[ratio ]P1.7,16. Vaccination of 4000 children, adolescents and close contacts of patients was also performed. After the intervention, 14 additional cases of meningococcal disease occurred, 8 due to the outbreak strain. However, incidence rates dropped from 180 to 30 per 100000 per year in the student population, but increased from 0 to 13 in the rest of the population in Nordhordland. Carriage eradication is not generally recommended in Norway. However, tracing and treating meningococcal carriage may have reduced transmission and disease in this outbreak situation.

To investigate the dynamics of nasopharyngeal colonization with Streptococcus pneumoniae, and to determine the prevalent serogroups/types (SGT) and their antimicrobial susceptibility, we studied 100 infants attending our well-baby clinic. Nasopharyngeal swab specimens were obtained at 6, 10, 14, 18 and 22 weeks and at 9 and 18 months of age and submitted for culture, serotyping and antimicrobial susceptibility testing of S. pneumoniae. Colonization with pneumococcus was seen on at least one occasion in 81 infants. The median age of acquisition was 11 weeks and the median duration of carriage was 1·3 months. The common SGTs identified were 6, 19, 14 and 15. SGT 1, which was a common invasive isolate in children in our hospital during this period, was not isolated from these children. Sequential colonization by 2, 3 or 4 SGTs was observed in 18, 5 and 2 children, respectively. Resistance to penicillin, chloramphenicol, cotrimoxazole and erythromycin was observed in 0, 13 (6%) 11 (5%) and 5 (3%) isolates, respectively. There was a significant difference in susceptibility to cotrimoxazole between colonizing and invasive isolates (5% vs. 40%, P<0·0001).

In May 1991 an immunization programme against Haemophilus influenzae type b (Hib) infection began within the Oxford region. We validate a deterministic mathematical model of Hib by comparison with the incidence of disease in the Oxford region, 1985–97. The comparison of model results with observed outcome allows an exploration of some of the poorly understood properties of the immunization programme. Model results and observed incidence are consistent with a vaccine that blocks the acquisition of carriage. Similarly, the data suggest that factors other than experience of Hib carriage are likely to have generated acquired immunity to Hib disease prior to the introduction of vaccination. Hence it is unlikely that waning of vaccine-derived protection will result in a resurgence of disease. The inclusion in the immunization schedule of a booster dose, as used in other countries, would have provided very little extra benefit.

Available data sources on disease due to Bordetella pertussis, including notifications, hospital admissions, deaths, and an enhanced laboratory-based surveillance system commenced in January 1994, were reviewed for the period 1995–7. Pertussis notifications continued their approximately 3-year cycle although at historically reduced levels. A slight seasonal increase in late summer/early autumn existed over and above a relatively constant background rate. Over time, the proportion of pertussis cases in younger, unvaccinated children, and to a lesser extent, adolescents and young adults, is increasing. There is a continuing significant and under- reported mortality associated with pertussis in the very young age group. Disease due to serotype 1,2 is on the increase despite persistent high vaccination levels and this serotype causes more severe disease. The provision of preventative antibiotics prior to disease onset reduced the severity of the disease but its use remains uncommon in England and Wales. While overall levels of pertussis notifications have declined in recent times, vaccination efficacy wanes with increasing age, and pertussis remains a significant cause of mortality and severe morbidity in the very young. This could be reduced by timely booster vaccination and increased recognition of mild disease in older cases followed by early antibiotic therapy for the very young household contacts.

Twenty-two strains of enteroaggregative Escherichia coli (EAggEC), isolated from four outbreaks of diarrhoeal disease in England, were examined for a range of phenotypic attributes including the ability to produce fimbriae, haemolysins and siderophores, and cell-surface properties such as surface charge and hydrophobicity. Strains of EAggEC isolated from two of these outbreaks belonged to a diverse range of serotypes and were heterogeneous in phenotype. Strains of EAggEC isolated from the other two outbreaks belonged predominantly to serotypes O86[ratio ]H34 and O98[ratio ]H-, respectively. Only two strains expressed fimbriae and two strains produced an 18 kDa membrane associated protein (MAP), suggesting that EAggEC express a range of adhesion mechanisms to produce the cell arrangement recognized as the ‘stacked brick’ formation. The possible explanation for the diversity of EAggEC serotypes is discussed.

Mouse virulence and the ability to adhere to, and invade cultured MDCK cells were investigated in 38 phage type reference strains of Salmonella enterica serotype Enteritidis and correlated with genomic lineage. The genomic lineage of 11 of the strains was determined in the present study; one IS200 and one ribotype pattern that had not been reported previously were observed. Log c.f.u. in the spleen 10 days post intraperitoneal (i.p.) infection with 3×103 bacteria (logVC10) varied between 2·9 and 8·7. The reference strains of PT7 and PT23 were found to be semi-rough and were of low virulence. All other strains possessed smooth LPS. Within each of the two major clonal lines, as well as among phage types outside these, both highly virulent and moderate to low virulent strains were present. While all strains of PT1, PT2 and PT8 were highly virulent, low virulent strains were detected in PT4 and PT13. The ability to adhere to, and invade MDCK cells varied between phage types (adherence between 13 and 61% of the inocula and invasion between 4 and 151% of the adherent cells). The results of the cell culture experiments did not correlate with the results of mouse virulence tests. No correlation between clonal lineage and virulence was found within S. Enteritidis. It seems most likely that some strains have lost some of the essential factors enabling this serotype to cause successful systemic infection.

The Traveller's Diarrhoea Network, by which the Infectious Disease Surveillance Center is electronically connected with two major airport quarantine stations and three infectious disease hospitals, was launched in February 1988 in Japan. The data on travellers' diarrhoea detected is reported weekly by e-mail. Two clusters of infection among travellers returning from Italy were reported by two airport quarantine stations at the end of September 1998. A total of 12 salmonella isolates from 2 clusters were examined. All were identified as Salmonella enteritidis, phage type 4 and showed identical banding patterns on pulsed-field gel electrophoresis. A case-control study showed that the scrambled eggs served at the hotel restaurant in Rome were the likely source of this outbreak. This outbreak could not have been detected promptly and investigated easily without the e-mail network. International exchange of data on travellers' diarrhoea is important for preventing and controlling food-borne illnesses infected abroad.

A cluster of acute melioidosis cases occurred in a remote, coastal community in tropical Western Australia. Molecular typing of Burkholderia pseudomallei isolates from culture-confirmed cases and suspected environmental sources by pulsed-field gel electrophoresis (PFGE) of XbaI chromosomal DNA digests showed that a single PFGE type was responsible for five cases of acute infection in a community of around 300 during a 5 week period. This temporal and geographical clustering of acute melioidosis cases provided a unique opportunity to investigate the environmental factors contributing to this disease. B. pseudomallei isolated from a domestic tap at the home of an asymptomatic seroconverter was indistinguishable by PFGE. Possible contributing environmental factors included an unusually acid communal water supply, unrecordable chlorine levels during the probable exposure period, a nearby earth tremor, and gusting winds during the installation of new water and electricity supplies. The possible role of the potable water supply as a source of B. pseudomallei was investigated further.

In a prison in Victoria, Australia, our objectives were contact tracing of inmates and staff at risk of exposure to an identified index case; and to determine risk factors for prevalent and incident infection. Inmates and staff who were potentially exposed to the index case were screened with a Mantoux skin test and a questionnaire. Inmate movements within the prison were compared to movements of the index case. Logistic regression was used to determine risk factors for infection. The index case had smear positive, cavitating pulmonary tuberculosis (TB), which was undiagnosed for 3 months. This was the period of potential exposure. The prevalence of positive skin test reactions in 190 inmates and staff at the prison was 10%. Significant predictors of a positive skin test were being an inmate (odds ratio (OR) 15·5), older age (OR 8·3) and being born overseas (OR 10·7). Bacille Calmette Guerin (BCG) vaccination, proximity to the index case in various prison sites, duration of incarceration, number of incarcerations and number of inmates per cell were not significant. There were three recent skin test conversions from negative to positive, representing a conversion rate of 3·5%. We did not find evidence of significant transmission of TB from a single index case. The prevalence of infection in this Australian prison was lower than published rates in other countries. Better prison conditions and different demographics of prison inmates in Australia may explain these differences.

This study compares the timing of the rise and decline of measles-specific IgM in serum samples and in oral fluid samples. Two hundred and eighty 9-month-old infants presenting for routine measles vaccination in Addis Ababa, Ethiopia, were enrolled. Paired serum and oral fluid samples were collected before and 1, 2, 3 or 4 weeks after measles vaccination. Samples were tested by using a modified antibody-capture enzyme immunoassay. For the 321 IgM-negative pre- and post-vaccination serum samples, 317 (99%) of their corresponding oral fluid samples were IgM-negative. Among the 130 IgM-positive serum samples, 75% of their paired oral fluid samples were IgM-positive, with the percentage rising to 87% after oral fluid samples collected [ges ]3·5 weeks after vaccination were excluded. Among the post-vaccination serum samples, the percent IgM-positive peaked in week 3 and declined to 79% in week 4. For post-vaccination oral fluid samples, the percent IgM-positive peaked in weeks 2 and 3, and then declined to 43% in week 4. This modified antibody-capture enzyme immunoassay appears to detect vaccine-induced measles-specific IgM in the first 3 weeks after vaccination.

Protozoa are important enteric pathogens in patients with human immunodeficiency virus (HIV) infection. In this study the prevalence of intestinal protozoa in 154 HIV-infected patients, with or without diarrhoea, in our region (Apulia, South Italy) was evaluated between December 1993 and February 1998. In the majority of patients CD4+ T cell count was below 200/μl. The overall prevalence of intestinal protozoa was 43/154 (27·92%). Twenty-eight (43·08%) out of 65 patients with diarrhoea and 15 (16·85%) out of 89 non-diarrhoeic patients were parasitized. In particular, in the group of 65 patients with diarrhoea the following protozoa were identified: Cryptosporidium parvum in 14 (21·54%), Blastocystis hominis in 7 (10·77%), microsporidia in 6 (9·23%), Giardia lamblia in 4 (6·15%) and Isospora belli in 1 (1·54%). Three patients were Cryptosporidium parvum-microsporidia co-infected. In patients without intestinal symptoms, prevalence was 3/89 (3·37%) for Cryptosporidium parvum, 9/89 (10·11%) for Blastocystis hominis, 1/89 (1·12%) for microsporidia and 2/89 (2·25%) for Giardia lamblia. A significant (P<0·001) correlation was observed between protozoan infection and the presence of diarrhoea. In particular, Cryptosporidium parvum and microsporidia infections were significantly (P<0·001) and P=0·046, respectively) associated with diarrhoeal illness. Moreover, the majority of cases of cryptosporidiosis were first diagnosed in the periods of heaviest rainfall. Therefore, drinking water contamination may be a possible source of human infection in our area.

Rates of acute hepatitis B are high in Moldova, but the prevalence of chronic infection is unknown. In 1994, we surveyed children and pregnant women, collected demographic information, and drew blood for laboratory testing. Among the 439 children (mean age, 5 years), the prevalence of antibody to hepatitis B core antigen (anti-HBc) and hepatitis B surface antigen (HBsAg) were 17·1 and 6·8%, respectively. Among the 1098 pregnant women (mean age, 26 years), 52·4% were anti-HBc-positive and 9·7% were HBsAg-positive. Of the HBsAg-positive pregnant women, 35·6% were hepatitis B e antigen (HBeAg) positive and 18·3% had antibodies to hepatitis D virus. The prevalence of antibody to hepatitis C virus was 1·4% in children and 2·3% in pregnant women. The high HBeAg prevalence among HBsAg-positive pregnant women and the high anti-HBc prevalence among children indicate that both perinatal and early childhood transmission contribute to the high hepatitis B virus endemicity in Moldova.

In April 1988, an outbreak of gastroenteritis occurred among employees in a large company in Helsinki, Finland. A retrospective cohort study, using a self-administered questionnaire, was carried out to ascertain the cause and extent of the outbreak. To meet the case definition, employees had to have had diarrhoea and/or vomiting since 2 April, 1998. A subanalysis was made in the biggest office, consisting of 360 employees, of whom 204 (57%) completed the questionnaire. Of these 108 (53%) met the case definition. Employees who had eaten raspberry dressing were more likely to meet the case definition than those who had not (Attack Rate (AR) 65% versus AR 18% Relative Risk, (RR) 3·7, 95%, Confidence Intervals (CI) 2·0–6·7). Four stool specimens obtained from affected kitchen staff who had all eaten the raspberry dressing and who had all become ill simultaneously with the employees were positive by polymerase chain reaction (PCR) for calicivirus. The data suggest that the primary source of the outbreak was imported frozen raspberries contaminated by calicivirus.

After a Christmas party in a restaurant, 48 (68%) of the 82 guests contracted calicivirus gastroenteritis. The epidemiological investigation showed that salad was strongly associated with the disease episode (RR=2·43, P=0·0005). Similar symptoms occurred among other customers who had had a meal at the same restaurant on the same evening. A foodhandler who had only prepared salad and appetizers became sick about 30 min after the end of his shift. He had been free of symptoms while preparing food. Few outbreak investigations have shown calicivirus transmission by foodhandlers some hours before becoming symptomatic.

We studied the relationship between age and prevalence, duration and incidence of clinical and laboratory evidence of ocular Chlamydia trachomatis infection in a cohort of Gambian subjects examined bi-weekly for 6 months. The duration of disease and infection, estimated by stratified survival analysis, proportional hazards regression and Weibull modelling, was markedly age-dependent. The estimated median duration of disease was 13·2 weeks in 0–4-year-old subjects and 1·7 weeks in those age 15 and over. Adjustment for multiple infections, and for missing observations did not alter this trend. The cumulative incidence rate of disease was reduced threefold with age. More rapid disease resolution is the main source of reduction in prevalence of active trachoma and ocular C. trachomatis infection with age; disease incidence was reduced to a lesser extent. This age-dependent resolution may be effected by adaptive cellular immune mechanisms. Mechanisms responsible for natural immunity should receive appropriate emphasis in vaccine design.

A mathematical model, based on a deterministic differential equation framework, has been developed to predict the impact of community chemotherapy programmes for human schistosomiasis. Here, this model is validated using data collected from a long-term control programme for urinary schistosomiasis on the island of Pemba, Zanzibar, United Republic of Tanzania, initiated in 1986 and still ongoing, in which schoolchildren were offered praziquantel chemotherapy every 6 months. Prevalence of infection and blood in urine were monitored in all the schools (total 26000 children from 60 schools) and more detailed data were collected in selected evaluation schools. Model predictions were run by using the initial prevalence as input. The predictions were very close to the observed decreases in prevalence and in prevalence of blood in urine. The correspondence improved further when the data were combined, going from single school level to district, and when the entire data set was combined. The accuracy of the predictions suggests that this model could be used as a tool to predict the consequences of chemotherapy control programmes. It is currently in press as a Windows software package under the name of ‘EpiSchisto’.

Accuracy assessment of diagnostic tests may be seriously biased if an imperfect reference test is used such as parasitology in the diagnosis of visceral leishmaniasis. We compared classical validity analysis of serological tests for Leishmania infantum with Latent Class Analysis (LCA), to assess whether it circumvented the gold standard problem. Clinical status, three serological tests (IFAT, ELISA and DAT) and parasitological data were recorded for 151 dogs captured in an endemic area. Sensitivity and specificity estimates from the 2×2 contingency tables were broadly corroborated by LCA, but the latter method provided more precise estimates that were robust for the different fitted models. It furthermore yielded a higher prevalence of infection and indicated that parasitology was only 55% sensitive. LCA seems a promising technique for test validation, but caution is required when applying it to sparse data sets. The feasibility and applicability of LCA in infectious disease epidemiology is discussed.

Invasive meningococcal disease (IMD) is thought to occur within a few days of pharyngeal acquisition of Neisseria meningitidis. During a longitudinal study of carriage and acquisition among 2453 first-year undergraduates we identified a male student from whom N. lactamica was isolated in October 1997 followed by N. meningitidis in December 1997. In mid-January 1998 this student suffered a mild episode of IMD (meningitis) during which N. meningitidis was isolated from his CSF. The meningococcus carried in December 1997 was phenotypically and genotypically indistinguishable from the invading organism, suggesting the possibility that the organism may have been carried for 7 weeks prior to the onset of invasive disease. Further studies are needed to assess more accurately the range of asymptomatic carriage prior to disease onset.