Relevance of epidemiological models depends on assumptions on the population structure and dynamics, on the biology of the host–parasite interaction, and on mathematical modelling. In this paper we reviewed published models of the bovine viral diarrhoea virus (BVDV) spread within a herd. Modelling options and assumptions on herd dynamics and BVDV transmission were discussed. A cattle herd is a population with a controlled size. Animals are separated into subgroups according to their age or their physiological status inducing heterogeneity of horizontal transmission. Complexity of models results from: (1) horizontal and vertical virus transmission, (2) birth of persistently infected animals, (3) excretion by transiently and persistently infected animals. Areas where there was a lack of knowledge were identified. Assumptions on the force of infection used to model the horizontal virus transmission were presented and discussed. We proposed possible ways of improving models (e.g. force of infection, validation) and essential model features for further BVDV models.

In Argentina, bovine leukaemia virus (BLV) infection is common in dairy herds. The country currently has a National Voluntary Control Programme but relatively few farms have enrolled. However, there is increased interest from authorities and farmers to implement regional compulsory programmes but there is scarce quantitative information of the transmission of BLV in cattle herds. This information is a prerequisite to develop effective BLV control strategies. Mathematical modelling offers ways of integrating population-level knowledge and epidemiological data to predict the outcomes of intervention scenarios. The purpose of the current paper is to gain understanding about the dynamics of the transmission of BLV in dairy herds from Argentina by simulation and to compare various BLV transmission models and select the one that is most appropriate. The hypothetical herd is conceptually described in terms of BLV status as a population of individuals that are protected by maternal antibodies (M), that are susceptible (S), that are in the latent period (E) or that are infectious (I). BLV is spread by horizontal and vertical transmission. We used an age-structured population model and within-herd transmission was simulated by Monte Carlo techniques. The next-generation approach has been used for the systematic computation of the basic reproduction ratio (R0). Parameter values for disease transmission were derived from previously published data; rates of entry, exit or transition between age groups were calculated based on our previous study, observational data, expert opinions and literature. With these parameter values the probability of a minor outbreak was estimated to be 10%, the probability of extinction was estimated as <0·001% and the expected time to extinction as more than 80 years. The probability of a minor outbreak and changes in prevalence were different when the index case was an adult cow compared to introduction by a heifer. Prediction of prevalences from MSI models fit the data satisfactorily. R0 was estimated as 9·5. The sensitivity analysis on R0 showed that all measures directed to reduce the transmission rate are potentially effective given operational control measures. An important prediction of these models is that, even in a relatively small, closed dairy herd, the time-scale for a BLV outbreak may be as long as several years and within-herd control of BLV requires intensive efforts.

Although pneumonic plague is listed by the Centers of Disease Control in the leading ‘critical biological agents’, very few studies exist on this subject. In this study, a mathematical compartment model was used to describe the geographical and temporal spread of an epidemic of pneumonic plague following its use as a biological weapon. Univariate and multivariate analyses were performed in order to assess the key parameters for the control of an outbreak in France. If interventions were taken 10 days after an attack, a reference scenario of 1000 index cases in Paris would lead to 2500 deaths. The results of the study indicate that the rapidity of onset of interventions has the largest effect on the final size of the epidemic, followed by wearing masks, treating contacts preventively and quarantine. Limiting inter-regional mixing does little to reduce casualties, although it does confine them to a single region.

The ecology of plague (Yersinia pestis infection) in its ancient foci in Central Asia remains poorly understood. We present field data from two sites in Kazakhstan where the great gerbil (Rhombomys opimus) is the major natural host. Family groups inhabit and defend burrow systems spaced throughout the landscape, such that the host population may be considered a metapopulation, with each occupied burrow system a subpopulation. We examine plague transmission within and between family groups and its effect on survival. Transmission of plague occurred disproportionately within family groups although not all gerbils became infected once plague entered a burrow system. There were no spatial patterns to suggest that family groups in close proximity to infected burrow systems were more at risk of infection than those far away. At one site, infection increased the chances of burrow-system extinction. Overall, it is useful to consider the burrow system as the unit of study within a much larger metapopulation.

A simulation model of a herd of grazing cattle, which has been developed to provide insight into the infection dynamics of E. coli O157 is described. The spatially explicit model enables the modelling of the infection transmission processes to be realistically addressed under field management conditions. The model is used to explore the efficacy of various potential control strategies in reducing the levels of within-herd infection. These measures include restricting the size of herds, niche engineering, improving housing hygiene and vaccination. While a vaccination strategy remains a hypothetical option, it has the potential to be particularly effective. It is likely that the most successful strategy will involve the implementation of a combination of measures.

The incidence of infection by mycobacteria, other than tubercle bacilli (MOTT) is increasing in the United Kingdom, Europe and the United States. These diseases increase morbidity and are an increasing public health concern. However, the epidemiology of disease due to these species is not well characterized. We used space–time clustering approaches and Generalized Linear Modelling to investigate the potential predictors of disease in cases of infection by organisms of the Mycobacterium avium complex (MAC) and M. malmoense recorded in the north of England during 2000–2005. There was significant spatial and temporal clustering in juvenile cases of infection by MAC but not for cases of infection in adults by either species. There were no significant predictors of infection by M. malmoense or juvenile cases of M. avium. Incidence of disease caused by M. avium in adults was significantly related to health deprivation and weakly related to rainfall. We consider possible reasons for the difference in epidemiology in infection by M. avium in adults and juveniles.

Vaccination has proved a powerful defence against measles. We reappraise measles seroepidemiological data in Taiwan from 1974 to 2004 having robust age-stratified serological information on exposure and immunity to quantitatively characterize measles vaccination programmes. We dynamically model measles seroepidemiology to estimate age-dependent intensity of infection associated with the effects of different contact patterns on pre- and post-vaccination. The WAIFM (who acquires infection from whom) contact matrix is employed to describe the transmission between and within each age group. A deterministic SEIR (susceptible–exposed–infected–recovery) model is used to capture subpopulation dynamics. Our study shows that mass regional or nationwide vaccination programmes could greatly reduce the potential for a major measles epidemic and have strong direct effects on the potential impact of childhood vaccination. We parameterize a predictive model that should reduce the socio-economic costs of measles surveillance in Taiwan and thereby encourage its continuance, especially for preschool children.

The aim of the European Sero-Epidemiology Network is to establish comparability of the serological surveillance of vaccine-preventable diseases in Europe. The designated reference laboratory (RL) for measles, mumps, rubella (MMR) prepared and tested a panel of 151 sera by the reference enzyme immunoassay (rEIA). Laboratories in 21 countries tested the panel for antibodies against MMR using their usual assay (a total of 16 different EIAs) and the results were plotted against the reference results in order to obtain equations for the standardization of national serum surveys. The RL also tested the panel by the plaque neutralization test (PNT). Large differences in qualitative results were found compared to the RL. Well-fitting standardization equations with R2⩾0·8 were obtained for almost all laboratories through regression of the quantitative results against those of the RL. When compared to PNT, the rEIA had a sensitivity of 95·3%, 92·8% and 100% and a specificity of 100%, 87·1% and 92·8% for measles, mumps and rubella, respectively. The need for standardization was highlighted by substantial inter-country differences. Standardization was successful and the selected standardization equations allowed the conversion of local serological results into common units and enabled direct comparison of seroprevalence data of the participating countries.

In September 2002, facsimiles were sent to 360 primary-care physicians alerting them to a local outbreak of Q fever. The physicians subsequently submitted serology samples on significantly more patients than in a previously comparable period in 2001. Facsimile cascade assists effective communication with primary-care physicians in an outbreak investigation.

Eight cases of Legionnaires' disease were identified among the 215 German passengers after a cruise to the Nordic Sea in August 2003. An unmatched case-control study was conducted to identify risk factors and the source of infection. In total, eight passengers fulfilled the case definition, one of these died. Forty-two passengers served as controls. The attack rate was 4%. The mean age was 60 years for cases and 62 years for controls. Prolonged exposure to the spa pool seemed to be a risk factor of infection (OR 4·85, P=0·09). Legionella pneumophila serogroup 1, monoclonal antibody (mAb) subgroup ‘Knoxville’ was isolated from clinical and environmental samples. DNA sequence-based typing revealed that these isolates were indistinguishable from each other. The investigation showed the importance of an interdisciplinary approach of microbiology and epidemiology as not all sites on the ship that tested positive for L. pneumophila actually posed a relevant risk for the passengers.

Legionnaires' disease (LD) is caused by Legionella species, most of which live in water. The Mid-Atlantic region experienced a sharp rise in LD in 2003 coinciding with a period of record-breaking rainfall. To investigate a possible relationship, we analysed the association between monthly legionellosis incidence and monthly rainfall totals from January 1990 to December 2003 in five Mid-Atlantic states. Using negative binomial model a 1-cm increase in rainfall was associated with a 2·6% (RR 1·026, 95% CI 1·012–1·040) increase in legionellosis incidence. The average monthly rainfall from May to September 1990–2002 was 10·4 cm compared to 15·7 cm from May to September 2003. This change in rainfall corresponds to an increased risk for legionellosis of approximately 14·6% (RR 1·146, 95% CI 1·067–1·231). Legionellosis incidence increased during periods of increased rainfall; identification of mechanisms that increase exposure and transmission of Legionella during rainfall might lead to opportunities for prevention.

Due to human error, drinking water supplied to a new housing estate in The Netherlands was contaminated with grey water. The cohort of 921 accidentally exposed households (area A) had a higher attack rate for diarrhoea (54·1%) than a non-exposed cohort of 1529 households from an adjacent area (B) (24%) (RR 2·3, 95% CI 1·9–2·7). Household water score showed a dose-response with illness, in both areas A and B. For each 1000 inhabitants, 19·8 cases in area A, 7·0 cases in control area B (RRAB 2·2, 95% CI 1·3–3·8) and 3·3 cases in a more distant control area C (RRAC 4·6, 95% CI 2·7–8·0) were diagnosed with gastroenteritis by their general practitioner. A gastroenteritis outbreak associated with consumption of contaminated drinking water was observed in the exposed area. The use of grey water was banned in 2003, with the exception of rainwater use for flushing toilets. The risk of rainwater use is currently being investigated.

On 3 February 2004, the Vermont Department of Health received reports of acute gastroenteritis in persons who had recently visited a swimming facility. A retrospective cohort study was conducted among persons attending the facility between 30 January and 2 February. Fifty-three of 189 (28%) persons interviewed developed vomiting or diarrhoea within 72 h after visiting the facility. Five specimens tested positive for norovirus and three specimen sequences were identical. Entering the smaller of the two pools at the facility was significantly associated with illness (RR 5·67, 95% CI 1·5–22·0, P=0·012). The investigation identified several maintenance system failures: chlorine equipment failure, poorly trained operators, inadequate maintenance checks, failure to alert management, and insufficient record keeping. This study demonstrates the vulnerability of recreational water to norovirus contamination, even in the absence of any obvious vomiting or faecal accident. Our findings also suggest that norovirus is not as resistant to chlorine as previously reported in experimental studies. Appropriate regulations and enforcement, with adequate staff training, are necessary to ensure recreational water safety.

Rotaviruses were detected by enzyme-linked immunosorbent assay (ELISA) in 92 out of 374 faecal samples collected between November 2003 and October 2004 at the Markaz Tebbi Koudakan Hospital, Tehran, Iran, from children aged 6 months to 5 years. Analysis of clinical and disease severity data showed a significant association between rotavirus infection and diarrhoea, vomiting and severe dehydration. Ninety-two samples (64 rotavirus ELISA-positive and 28 ELISA-negative samples) were sent to the Enteric Virus Unit, Virus Reference Department, Centre for Infection, Health Protection Agency, UK for rotavirus characterization by G-typing, P-typing and subgrouping (SG) using reverse transcriptase (RT)–PCR, semi-nested PCR and sequencing methods. In this study, both common and uncommon rotavirus genotypes were detected. The most prevalent types were G1P[8], SGII (59·2%) followed by G9P[8] SGII (15·5%) which has not been previously reported from Iran. Unusual genotypes G1P[10] SGI (2·8%) and G12P[8] SGII (1·4%) and strains derived from reassortment between common co-circulating genotypes such as G1P[4] SGII represented 5·6% of strains. Mixed infections with combinations of G1+G4P[8] SGII and G1+G9P[8] SGII were also found. This contrasts with previous reports from Iran in which a small number of common rotavirus strains (G1 and G4) were found. This study highlights the need for continued surveillance and characterization of rotaviruses to take account of the rapid evolution and introduction of novel rotaviruses into the human population.

Specimens of human faeces were tested by a rapid strategy for detection of Campylobacter jejuni lineages by the presence of specific single nucleotide polymorphisms (SNPs) based on the C. jejuni multi locus sequence typing (MLST) scheme. This strategy was derived from analysis of the MLST databases to identify clonal complex specific SNPs followed by the design of real-time PCR assays to enable identification of six major C. jejuni clonal complexes associated with cases of human infection. The objective was to use the MLST SNP-based assays for the direct detection of C. jejuni by clonal complex from specimens of human faeces, and then confirm the accuracy of the clonal complex designation from the SNP-based assays by performing MLST on the cultured faecal material, this targeted at determining the validity of direct molecular specimen identification. Results showed it was possible to identify 38% of the isolates to one of the six major MLST clonal complexes using a rapid DNA extraction method directly from faeces in under 3 h. This method provides a novel strategy for the use of real-time PCR for detection and characterization beyond species level, supplying real-time epidemiological data, which is comparable with MLST results.

Antibiotic resistance data, made available from laboratory records during eight cholera outbreaks between 1990 and 2004 showed Vibrio cholerae serogroup O1 to have a low level of resistance (2–3%) to tetracycline during 1990–1991. Resistance increased for tetracycline (95%), chloramphenicol (78%), doxycycline (70%) and trimethoprim–sulphamethoxazole (97%) in subsequent outbreaks. A significant drop in resistance to tetracycline and chloramphenicol followed the adoption of a national policy to replace tetracycline with erythromycin for treating cholera. Sixty-nine strains from cholera outbreaks in Zambia between 1996 and 2004, were examined for antibiotic resistance and basic molecular traits. A 140 MDa conjugative, multidrug-resistant plasmid was found to encode tetracycline resistance in strains from 1996/1997 whereas strains from 2003/2004 were resistant to furazolidone, but susceptible to tetracycline, and lacked this plasmid. PCR revealed 25 of 27 strains from 1996/1997 harboured the intl1 class 1 integron but lacked SXT, a conjugative transposon element. Similar screening of 42 strains from 2003/2004 revealed all carried SXT but not the intl1 class 1 integron. All 69 strains, except two, one lacking ctxA and the other rstR and thus presumably truncated in the CTX prophage region, were positive for important epidemic markers namely rfbO1, ctxA, rstR2, and tcpA of El Tor biotype. Effective cholera management is dependent on updated reports on culture and sensitivity to inform the choice of antibiotic. Since the emergence of antibiotic resistance may significantly influence strategies for controlling cholera, continuous monitoring of epidemic strains is crucial.

Two variants of Listeria monocytogenes were isolated from blood cultures from each of two patients with listeriosis. Each variant displayed a two-band difference in DNA profile from the other by pulsed-field gel electrophoresis. Although this difference in profile is insufficient to distinguish clearly between the variants, the possibility of co-infection with different strains of L. monocytogenes needs to be considered. We suggest that more than one colony should be selected for molecular typing to aid interpretation during investigation of the sources and routes of Listeria infection.

Reduction of the antioxidant capacity of plasma has been linked with the impairment of an effective immune response and so we hypothesized that the carriage rate of Neisseria meningitidis in asymptomatic subjects might correlate with the levels of antioxidants in plasma. To this end we took pharyngeal swabs from 339 children in Marquesado Basic Health Zone, Granada, Spain and in addition determined the total antioxidant capacity (TAC) in plasma samples from these subjects. The overall prevalence of N. meningitidis carriage was 5·9% (mean age 7·1 years) with rates of 10·3% in children aged ⩽3 years, 3·9% between 4 and 7 years and 2·4% in older subjects. Plasma TAC for the ⩽3-year-olds was 0·13 for carriers and 1·10 for non-carrier controls (P=0·04), 0·13 for carriers aged 4–7 years (controls 0·63) and 0·28 for carriers aged >7 years (controls 0·52). We analysed the association between TAC in plasma (<0·37 – 2 s.d.) and the carrier state of N. meningitidis. In the carrier state, the odds ratio for this association (TAC in plasma <0·25) was 8·44 (95% CI 1·5–48·9). These findings may suggest a reduced immune response in the host favourable to nasopharyngeal persistence of meningococci.

Enhanced surveillance for Hib infection, initially covering Wales and five English regions, began in 1990 and in 1995 was extended to the whole of England and Wales. To determine whether changes in the ascertainment of Haemophilus influenzae may have affected estimates of Hib disease incidence, data from January 1990 to December 2003 were analysed. A total of 8887 and 4020 (45%) cases of H. influenzae and Hib respectively were reported. The proportion of isolates that were serotyped increased over time, and therefore reported incidence may have underestimated the true incidence in the early years of the study. Adjusting for this under-ascertainment, the incidence in children aged <5 years declined from a peak of 28·3/100 000 in 1991 to 0·97/100 000 in 1998 and increased to 3·8/100 000 in 2003. Following the implementation of universal vaccination a dramatic decline in the true incidence of invasive Hib disease occurred. The observation of the subsequent resurgence was real but the highest incidence reached was 85% below the corrected incidence in the pre-vaccine era. Continued high-quality surveillance is needed in order to accurately monitor and detect changes in disease incidence.