Between December 1997 and January 1998 an increase in the number of isolates of Salmonella enterica serovar Newport, a serotype rarely causing indigenous infections in Finland, was detected. This included two clusters of gastroenteritis following funeral meals. An inquiry via Enter-net revealed a concomitant increase in cases of S. Newport in the United Kingdom. To investigate the Finnish outbreak, a total of 56 S. Newport strains (22 from the outbreak period, 27 from pre- and post-outbreak period, and 7 from imported food producing animals) were studied by pulsed-field gel electrophoresis (PFGE); selected isolates were also phage typed. Two retrospective questionnaire studies evaluating food exposures among the funeral attendants were conducted. All isolates from the clusters had an identical PFGE pattern which was also found in 13 infections temporally close to but not associated with the clusters. The Finnish outbreak was caused by the same phage type as the one in the United Kingdom. In both clusters, an epidemiological link between illness and exposure to cured ham was found. In conclusion, the outbreak was not limited to the two clusters but was more widely spread both in and outside Finland. Early alarm systems of food-borne outbreaks and collaboration between European countries are needed for investigating international outbreaks.

Salmonella Typhimurium definitive type 104 with chromosomally encoded resistance to five or more antimicrobial drugs (R-type ACSSuT+) has been reported increasingly frequently as the cause of human and animal salmonellosis since 1990. Among animal isolates from the northwestern United States (NWUS), R-type ACSSuT+ Typhimurium isolates increased through the early 1990s to comprise 73% of Typhimurium isolates by 1995, but subsequently decreased to comprise only 30% of isolates during 1998. NWUS S. Typhimurium R-type ACSSuT+ were consistently (99%) phage typed as DT104 or the closely related DTu302. S. Typhimurium isolates from cattle with primary salmonellosis, randomly selected from a national repository, from NWUS were more likely to exhibit R-type ACSSuT+ (19/24, 79%) compared to isolates from other quadrants (17/71, 24%; P < 0.01). Human patients infected with R-type ACSSuT+ resided in postal zip code polygons of above average cattle farm density (P < 0.05), while patients infected with other R-types showed no similar tendency. Furthermore, humans infected with R-type ACSSuT+ Typhimurium were more likely to report direct contact with livestock (P < 0.01) than humans infected with other R-types.

Vellore is endemic for cholera due to Vibrio cholerae O1 and O139. In a previous study the prevalence of Vibrio cholerae in drinking water, lakes and sewage outfalls in a single 2-months period in Vellore, India was determined. In addition water samples from three sites were also tested for the presence of V. cholerae O1 and O139 by fluorescent antibody staining. This follow on study has examined how the environmental distribution of V. cholerae at the same sites alters over a 12-month period and the relationship to the clinical pattern of cholera in Vellore. Samples of water were collected from fixed sites at three water bodies each month between April 1997 and March 1998. Bacteria isolated from samples were identified by standard biochemical tests and isolated strains of V. cholerae tested for their ability to agglutinate O1 and O139 antisera. Samples were also tested for the presence of V. cholerae O1 and O139 by fluorescent antibody staining. The clinical isolation rate of V. cholerae in Vellore, maximum temperature and rainfall were also studied. The results demonstrate the presence in the environment of viable but non-cultivable (VNC) V. cholerae in 10 of 12 months of the study year as well as their viability. Their prevalence in the environment also correlated with the isolation of these pathogens from clinical samples over the same study period.

Between April 1996 and March 1997 we examined 5093 samples of raw beef and lamb products for the presence of E. coli O157. Samples were purchased from 81 small butchers' shops in south Yorkshire. In March 1997 we also examined five samples of dried mint for the presence of E. coli O157.

Strains of E. coli O157 were isolated by enrichment culture in modified buffered peptone water followed by immunomagnetic separation and culture of magnetic beads onto cefixime tellurite sorbitol MacConkey agar. Strains were characterized by phage typing, toxin genotyping and plasmid analysis.

Strains of E. coli O157 were isolated from 72 (1·4%) of 5093 samples; it was isolated from 36 (1·1%) of 3216 samples of beef products and from 29 (2·9%) samples of lamb products. The highest prevalence was found in lamb sausages and lamb burgers where E. coli O157 was isolated from 3 (4·1%) of 73 and 18 (3·7%) of 484 samples respectively. Strains of E. coli O157 were isolated most frequently during early summer. Strains of E. coli O157 were also isolated from 2 of 5 samples of dried mint although we did not determine how the mint had become contaminated.

All isolates of E. coli O157 were Verocytotoxin-producing as determined by both Vero cell assay and DNA hybridization for the genes encoding Verocytotoxin and all were positive for the eaeA gene. A combination of phage typing, toxin genotyping and plasmid profile subdivided the 72 strains of E. coli isolated into 20 different subtypes, of which 18 were indistinguishable from strains isolated previously from cattle and sheep; of these 18 strains, 8 were indistinguishable from strains isolated from human cases of infection during the study period.

We conducted a study to determine the incidence of haemolytic uraemic syndrome (HUS) in children in France and to assess the role of Shiga-toxin-producing Escherichia coli (STEC) infection in the aetiology of HUS. In collaboration with the Société de Néphrologie Pédiatrique we undertook a retrospective review of all cases of HUS hospitalized from January 1993 to March 1995 and a 1-year prospective study (April 1995–March 1996) of epidemiological and microbiological features of cases of HUS. The polymerase chain reaction (PCR) procedure was used to detect stx, eae, e-hlyA genes directly from case stool samples. Serum samples from cases were examined for antibodies to lipopolysaccharide (LPS) of 26 major STEC serogroups. Two hundred and eighty-six cases were reported. The average incidence per year was 0·7/105 children < 15 years and 1·8/105 children < 5 years. During the prospective study, 122/130 cases were examined for evidence of STEC infection using PCR and/or serological assays and 105 (86%) had evidence of STEC infection. Serum antibodies to E. coli O157 LPS were detected in 79 (67%) cases tested. In conclusion, this study showed that STEC infection is an important cause of HUS in children in France, with a high proportion related to the O157 serogroup.

We examined the incidence rate and prognosis of tuberculosis in a cohort of patients with liver cirrhosis in Denmark. In a study cohort of 22675 patients with liver cirrhosis, we identified 151 cases of tuberculosis from 1977 to 1993. The incidence rate was 168·6 per 100000 person-years of risk, and the highest incidence rate was among men above 65 years of age, with an incidence rate of 246·0 per 100000 person-years of risk. The 30-day case-fatality rate was 27·3% and the 1-year case fatality rate was 47·7%. The results demonstrate that patients with liver cirrhosis are at increased risk of tuberculosis. Additionally, it is suggested that liver cirrhosis is an independent risk factor for tuberculosis, and that patients with liver cirrhosis who acquire tuberculosis have a poor prognosis.

A sample of 35 pyrazinamide (PZA)-resistant and 30 PZA-susceptible clinical isolates recovered from Beijing and Taiyuan City, China were characterized by SSCP and sequence analysis for mutations in the pncA gene that encodes the Mycobacterium tuberculosis PZase. The purpose of this study was to understand the molecular basis and the characteristics of pncA gene mutations and its relation to PZA resistance in M. tuberculosis strains from China. Several mutations with base changes leading to amino acid substitutions were found in the PZA-resistant isolates. No mutations were seen in the 243 PZA-susceptible isolates. Among the 35 PZA-resistant isolates, 32 isolates (91·4%) had nucleotide substitutions, insertions and deletions that resulted in amino-acid substitution; or frameshifts in some strains. Other previously uncharacterized mutations were found as follows: Asn118→Thr, CG insertion at position 501; CC insertion at nucleotide position 403; a 8 base-pair deletion at start codon; Pro54→Thr; AG insertion at 368; Tyr41→His, Ser88→stop, and A insertion at nucleotide position 301. IS6110 subtyping revealed that each strain was unique; indicative of the epidemiologic independence of the isolates.

The purposes of this study were to determine whether microorganisms can be isolated from the membranes of stethoscopes used by clinicians and nurses, and to analyse whether or not the degree of bacterial colonization could be reduced with different cleaning methods. We designed a transversal before-after study in which 122 stethoscopes were examined. Coagulase negative staphylococci (which are also potentially pathogenic microorganisms) were isolated together with 13 other potentially pathogenic microorganisms, including S. aureus, Acinetobacter sp. and Enterobacter agglomerans. The most effective antiseptic was propyl alcohol. Analysis of the cleaning habits of the Emergency Department (ED) staff, showed that 45% cleaned the stethoscope annually or never. The isolation of potentially pathogenic microorganisms suggests that the stethoscope must be considered as a potential vector of infection not only in the ED but also in other hospital wards and out-patient clinics.

Aboriginal Australians in northern Australia are subject to endemic infection with group A streptococci, with correspondingly high rates of acute rheumatic fever and rheumatic heart disease. For 12 communities with good ascertainment, the estimated lifetime cumulative incidence of acute rheumatic fever was approximately 5·7%, whereas over the whole population, with less adequate ascertainment, the cumulative incidence was only 2·7%. The corresponding prevalences of established rheumatic heart disease were substantially less than the cumulative incidences of acute rheumatic fever, at least in part because of poor ascertainment. The cumulative incidence of acute rheumatic fever estimates the proportion of susceptible individuals in endemically exposed populations. Our figures of 2·7–5·7% susceptible are consistent with others in the literature. Such comparisons suggest that the major part of the variation in rheumatic fever incidence between populations is due to differences in streptococcal exposure and treatment, rather than to any difference in (genetic) susceptibility.

Incidence data by age of new episodes of influenza-like illness reported by sentinel general practice networks in England and Wales and in The Netherlands over a 10-year period were examined to provide estimates of the consulting population during influenza epidemic periods. Baseline levels of recording in each age group were calculated from weeks in which influenza viruses were not circulating and the excess over baseline calculated to provide the population estimates during influenza epidemics.

Influenza A/H3N2 epidemics were associated with higher population estimates for consultations than influenza B, especially in the age groups 0–4 and 65 years and over. In the intervening age groups, population estimates were more consistent regardless of the virus type. Both networks reported simultaneous peaking of incidence rates in all of the age groups. There were substantial increases in the number of persons reporting other respiratory illnesses during influenza epidemics.

Population estimates of the consulting population provide the only secure basis for which health services resource utilization during influenza epidemics can be estimated.

To estimate the immunity of the Dutch population against vaccine-preventable diseases, a population-based serum bank was established. Since a multi-tiered approach to enrol eligible individuals was used, both the overall non-response selection and the effect, on this selection, of including additional participants and of excluding a subgroup of non-participants (i.e. those without questionnaire data) could be studied. For some characteristics associated with non-participation, an association with seroprevalence of vaccine-preventable diseases is likely (e.g. age, gender). For other characteristics (e.g. marital status, receipt of reminder, degree of urbanization) the association with immune status is unclear but probably small. If the distribution in the population, or information on all participants and non-participants, of the characteristic is available, then the effect on the seroprevalence can be estimated. However, investigators have to be aware that studying only a subgroup of non-participants might lead to a biased insight into non-participation selection. Furthermore, merely including additional participants might not always reduce this bias.

Failure to seroconvert (primary vaccine failure) is believed to be the principal reason (approx. > 95%) why some vaccinees remain susceptible to measles and is often attributed to the persistence of maternal antibodies in children vaccinated at a young age. Avidity testing is able to separate primary from secondary vaccine failures (waning and/or incomplete immunity), but has not been utilized in measles epidemiology. Low-avidity (LA) and high-avidity (HA) virus-specific IgG antibodies indicate primary and secondary failure, respectively. Measles vaccine failures (n = 142; mean age 10·1 years, range 2–22 years) from an outbreak in 1988–9 in Finland were tested for measles–virus IgG avidity using a protein denaturating EIA. Severity of measles was recorded in 89 failures and 169 non-vaccinees (mean age 16·2 years, range 2–22 years). The patients with HA antibodies (n = 28) tended to have clinically mild measles and rapid IgG response. Among failures vaccinated at < 12, 12–15 and > 15 months of age with single doses of Schwarz-strain vaccine in the 1970s, 50 (95% CI 1–99), 36 (CI 16–56) and 25% (CI 8–42) had HA antibodies, respectively. When a single measles, mumps and rubella (MMR) vaccine had been given after 1982 at 15 months of age, only 7% (CI 0–14) showed HA antibodies. Omitting re-vaccinees and those vaccinated at < 15 months, Schwarz-strain recipients had 3·6 (CI 1·1–11·5) higher occurrence of HA responses compared to MMR recipients. Apart from one municipality, where even re-vaccinees had high risk of primary infection, 89% (CI 69 to ∼ 100) of the infected re-vaccinees had an HA response. Secondary measles-vaccine failures are more common than was more previously thought, particularly among individuals vaccinated in early life, long ago, and among re-vaccinees. Waning immunity – even among individuals vaccinated after 15 months of age, without the boosting effect of natural infections should be considered a relevant possibility in future planning of vaccination against measles.

From March to July 1996 a measles outbreak occurred in northern Luxembourg with 110 reported cases centered around two primary schools (85 cases) and the surrounding community (25 cases). Eighty four suspected cases were confirmed serologically. Vaccine coverage was estimated from questionnaire-based surveys at the two primary schools to be 70 and 76%, respectively. Vaccine efficacy during the outbreak was estimated to be 94.6% [95% confidence interval (CI) 90·4–97·0]. Using the information from the school surveys, we obtained estimates of the basic reproduction number of measles of 7·7 (95% CI 4·4–11·0) and 6·2 (95% CI 3·5–8·9), respectively. Assuming a 95% vaccine efficacy, these estimates correspond to minimal vaccine coverages of 91·6% (95% CI 81·4–95·7) and 88·3% (95% CI 75·5–93·4) which would have been necessary to minimize the chances of a major outbreak occurring. We can confirm that major outbreaks in similar school settings can only be prevented if vaccination coverage exceeds 90%.

A mathematical model of the dynamics of measles in New Zealand was developed in 1996. The model successfully predicted an epidemic in 1997 and was instrumental in the decision to carry out an intensive MMR (measles–mumps–rubella) immunization campaign in that year. While the epidemic began some months earlier than anticipated, it was rapidly brought under control, and its impact on the population was much reduced. In order to prevent the occurrence of further epidemics in New Zealand, an extended version of the model has since been developed and applied to the critical question of the optimal timing of MMR immunization.

Epidemiological and clinical findings from 1162 serologically confirmed measles cases occurring in Buenos Aires, Argentina in 1997 and 1998 were retrospectively reviewed. From 90 hospitalized children, measles virus was detected by direct RT–PCR from nasopharyngeal secretions. Patients were grouped as follows: (i) not vaccinated: infants < 12 months; (ii) regularly vaccinated: children 1–4 years not covered by the last catch-up; (iii) catch-up vaccinated: patients 5–19 years immunized during the 1993 campaign. Most cases were recorded in non-vaccinated infants (54%), and the lowest in catch-up vaccinated children (16%). Mean age of the 90 hospitalized children was 11·3 months. Pneumonia was the major hospitalization cause followed by pneumonitis. Two children required intensive care and one died. The 1993 catch-up campaign seemed to reduce the number of cases in the 5- to 19-year-old group. Lack of timely follow-up probably led to the accumulation of susceptible individuals allowing measles re-emergence. Direct viral detection by RT–PCR proved to be a sensitive tool for molecular epidemiology surveillance.

Vaccine escape variants of hepatitis B virus (HBV) have been identified world-wide. A mathematical model of HBV transmission is used to investigate the potential pattern of emergence of such variants. Attention is focused on The Gambia as a country with high quality epidemiological data, universal infant immunization and in which escape mutants after childhood infections have been observed. We predict that a variant cannot become dominant for at least 20 years from the start of vaccination, even when using a vaccine which affords no cross protection. The dominant factor responsible for this long time scale is the low rate of infectious contacts between infected and susceptible individuals (we estimate the basic reproduction number of hepatitis B in The Gambia to be 1·7). A variant strain that achieves high prevalence will also take many years to control, and it is questionable whether emergence will be identifiable by sero-surveillance until of high prevalence. The sensitivity of the model predictions to epidemiological and demographic factors is explored.

An outbreak of hepatitis A occurred in a religious community in Indiana, USA. Sixty-nine cases were ascertained among the 4466 residents over a year, and the highest attack rate was in children. The management of the outbreak included the widespread use of prophylactic immune serum globulin (ISG). Despite this, further cases occurred. To guide further ISG administration, a survey was undertaken to ascertain what proportion remained susceptible to HAV infection. From a random sample of 600 people in the affected community 440 saliva specimens (73%) were obtained. Of these, 12·5% were found to be immune (95% confidence intervals from 9–16%). No changes were made to the ISG administration policy. There was no evidence to suggest that administration of ISG had any effect on the duration of the outbreak. There was a low rate of symptomatic infection among young children (less than 10 years); as ISG does not prevent the spread of the virus its use is not recommended in future outbreak situations.

Samples of blood, spleen and legs from 112 culled roe deer (Capreolus capreolus) were collected from nine sites widespread in the United Kingdom. The prevalence of infection with Ehrlichia phagocytophila was determined by serology and polymerase chain reaction. Means of 58% of 102 plasma or serum samples were seroreactive by IFA, 38% of 84 blood samples and 29% of 82 spleen samples were positive by PCR. Ticks on legs of 71 roe deer were Ixodes ricinus larvae, nymphs and adults and 83% of legs were infested. Numbers of ticks corresponded positively to the percentage of samples positive for E. phagocytophila by serology and PCR for different sampling sites. Ixodes ricinus nymphs collected from the vegetation at one site with infected deer were analysed for infection with E. phagocytophila by examination of Feulgen stained salivary glands. Of 135 nymphs 5% were infected. These results confirm that roe deer are commonly parasitized by both E. phagocytophila and its vector tick in such a way that it is likely to be an important natural mammalian reservoir of E. phagocytophila.

A prospective cohort study was conducted in five purposively-sampled agro-ecological zone (AEZ)-grazing system strata in Murang’a District, Kenya, between March 1995 and June 1996. The study strata were selected based on a preliminary characterization study to represent the widest range of risks to East Coast fever (ECF) in the District and included zero-grazing and open-grazing farms. In total, 225 calves from 188 smallholder farms were examined from birth to 6 months of age and visited within the first 2 weeks of life and thereafter at bi-weekly intervals for up to 14 visits.

The purpose of the study was to characterize the differences in epidemiology (risks of infection, morbidity and mortality) and potential control of ECF between the selected strata. Evidence of Theileria parva infection was assessed by increased antibody levels as measured in an indirect ELISA assay by the percent positivity (PP) of serum samples relative to a strong positive reference serum.

Sero-conversion risks of T. parva were highest in the open-grazing strata. Antibody prevalence in adult cattle and ECF morbidity and mortality risks were also highest in open-grazing strata. While different, all five AEZ-grazing strata were considered to be endemically unstable for ECF. East Coast fever challenge was low in all zero-grazing strata and this challenge is likely to remain low due to continuing intensification of smallholder farming in the central highlands. In the open-grazing strata, there was higher challenge and a greater impact of ECF.

The distribution of the meningococcal insertion sequence IS1301 was analysed in 496 strains of different serogroups and clonal lineages of Neisseria meningitidis, and in 64 neisserial strains other than N. meningitidis. IS1301 was found in meningococci, but not in apathogenic Neisseria sp. and Neisseria gonorrhoeae. The copy numbers of IS1301 varied between 2 and 17 per genome. IS1301 positive strains were mostly found among the serogroups 29E, W135, X, and Y. Clonal lineages of serogroup A, B, and C meningococci associated with epidemic meningococcal disease were rarely positive for IS1301.