The epidemiology of human campylobacteriosis is complex but in recent years understanding of this disease has advanced considerably. Despite being a major public health concern in many countries, the presence of multiple hosts, genotypes and transmission pathways has made it difficult to identify and quantify the determinants of human infection and disease. This has delayed the development of successful intervention programmes for this disease in many countries including New Zealand, a country with a comparatively high, yet until recently poorly understood, rate of notified disease. This study investigated the epidemiology of Campylobacter jejuni at the genotype-level over a 3-year period between 2005 and 2008 using multilocus sequence typing. By combining epidemiological surveillance and population genetics, a dominant, internationally rare strain of C. jejuni (ST474) was identified, and most human cases (65·7%) were found to be caused by only seven different genotypes. Source association of genotypes was used to identify risk factors at the genotype-level through multivariable logistic regression and a spatial model. Poultry-associated cases were more likely to be found in urban areas compared to rural areas. In particular young children in rural areas had a higher risk of infection with ruminant strains than their urban counterparts. These findings provide important information for the implementation of pathway-specific control strategies.

Diarrhoea is a leading cause of morbidity and mortality yet diarrhoea specific incidence and mortality rates for older children, adolescents, and adults have not been systematically calculated for many countries. We conducted a systematic literature review to generate regional incidence rates by age and to summarize diarrhoea specific mortality rates for regions of the world with inadequate vital registration data. Diarrhoea morbidity rates range from 29·9 episodes/100 person-years for adults in the South East Asian region to 88·4 episodes/100 person-years in older children in the Eastern Mediterranean region and have remained unchanged in the last 30 years. Diarrhoea mortality rates decline as the child ages and remain relatively constant during adulthood. These data are critical for improving estimates worldwide and further highlight the need for improved diarrhoea specific morbidity and mortality data in these age groups.

Despite the frequency of Campylobacter as the principal cause of bacterial gastroenteritis in the UK, outbreaks attributed to this pathogen are rare. One hundred and fourteen general foodborne outbreaks of campylobacteriosis were reported to the Health Protection Agency from 1992 to 2009 with most occurring in food service establishments (64%, 73/114). Poultry meat (38%, 43/114) was the most commonly reported vehicle of infection, of which poultry liver pâté, and undercooking, were strongly associated with this pathogen. Notably, the number of outbreaks of campylobacteriosis linked to consumption of poultry liver pâté in England and Wales increased significantly from 2007 (74% as opposed to 12%, P<0·00001) with a preponderance of these occurring in December. These outbreaks highlight the hazards associated with inappropriate culinary practices leading to undercooking of poultry liver pâté and suggest that improving catering practice is an important last line of defence in reducing exposure to Campylobacter-contaminated products.

The dramatic decline of the native red squirrel in the UK has been attributed to both direct and disease-mediated competition with the grey squirrel where the competitor acts as a reservoir host of squirrelpox virus (SQPV). SQPV is threatening red squirrel conservation efforts, yet little is known about its epidemiology. We analysed seroprevalence of antibody against SQPV in grey squirrels from northern England and the Scottish Borders in relation to season, weather, sex, and body weight using Generalized Linear Models in conjunction with Structural Equation Modelling. Results indicated a heterogeneous prevalence pattern which is male-biased, increases with weight and varies seasonally. Seroprevalence rose during the autumn and peaked in spring. Weather parameters had an indirect effect on SQPV antibody status. Our findings point towards a direct disease transmission route, which includes environmental contamination. Red squirrel conservation management options should therefore seek to minimize squirrel contact points.

A correlation between national pig-meat consumption and mortality rates from chronic liver disease (CLD) across developed countries was reported in 1985. One possible mechanism explaining this may be hepatitis E infection spread via pig meat. We aimed to re-examine the original association in more recent international data. Regression models were used to estimate associations between national pig-meat consumption and CLD mortality, adjusting for confounders. Data on CLD mortality, alcohol consumption, hepatitis B virus (HBV) and hepatitis C virus (HCV) seroprevalence for 18 developed countries (1990–2000) were obtained from WHO databases. Data on national pig-meat and beef consumption were obtained from the UN database. Univariate regression showed that alcohol and pig-meat consumption were associated with mortality from CLD, but beef consumption, HBV and HCV seroprevalence were not. A 1 litre per capita increase in alcohol consumption was associated with an increase in mortality from CLD in excess of 1·6 deaths/100 000 population. A 10 kg higher national annual average per capita consumption of pork meat was associated with an increase in mortality from CLD of between 4 and 5 deaths/100 000 population. Multivariate regression showed that alcohol, pig-meat consumption and HBV seroprevalence were independently associated with mortality from CLD, but HCV seroprevalence was not. Pig-meat consumption remained independently associated with mortality from CLD in developed countries in the 1990–2000 period. Further work is needed to establish the mechanism.

Until recently, reports on methicillin-resistant Staphylococcus aureus (MRSA) in food production animals were mainly limited to occasional detections in dairy cattle mastitis. However, since 2005 a MRSA clone, CC398, has been reported colonizing pigs, veal calves and broiler chickens and infecting dairy cows. Many aspects of its prevalence in pigs remain unclear. In other livestock, colonizing capacity and reservoir status still require elucidation. MRSA CC398 has also been detected in meat, but, as for other MRSA, the risk this poses is somewhat unclear. Currently, the most worrying aspect of MRSA CC398 appears to be its capacity to spread to humans. This might complicate MRSA control measures in human healthcare, urging research into risk factors and transmission routes. Although infections with MRSA CC398 are much less reported than carriage, more investigation into its pathogenic potential is required. Moreover, the origin and evolution of this clone remain unknown.

The force of infection, describing the rate at which a susceptible person acquires an infection, is a key parameter in models estimating the infectious disease burden, and the effectiveness and cost-effectiveness of infectious disease prevention. Since Muench formulated the first catalytic model to estimate the force of infection from current status data in 1934, exactly 75 years ago, several authors addressed the estimation of this parameter by more advanced statistical methods, while applying these to seroprevalence and reported incidence/case notification data. In this paper we present an historical overview, discussing the relevance of Muench's work, and we explain the wide array of newer methods with illustrations on pre-vaccination serological survey data of two airborne infections: rubella and parvovirus B19. We also provide guidance on deciding which method(s) to apply to estimate the force of infection, given a particular set of data.

A previous mathematical model explaining dengue in Singapore predicted a reasonable outbreak of about 6500 cases for 2006 and a very mild outbreak with about 2000 cases for 2007. However, only 3051 cases were reported in 2006 while more than 7800 were reported in the first 44 weeks of 2007. We hypothesized that the combination of haze with other local sources of particulate matter had a significant impact on mosquito life expectancy, significantly increasing their mortality rate. To test the hypothesis a mathematical model based on the reproduction number of dengue fever and aimed at comparing the impact of several possible alternative control strategies was proposed. This model also aimed at contributing to the understanding of the causes of dengue resurgence in Singapore in the last decade. The model's simulation demonstrated that an increase in mosquito mortality in 2006 and either a reduction in mortality or an increase in the carrying capacity of mosquitoes in 2007 explained the patterned observed in Singapore. Based on the model's simulation we concluded that the fewer than expected number of dengue cases in Singapore in 2006 was caused by an increase in mosquito mortality due to the disproportionate haze affecting the country that year and that particularly favourable environmental conditions in 2007 propitiated mosquitoes with a lower mortality rate, which explains the greater than expected number of dengue cases in 2007. Whether our hypothesis is plausible or not should be debated further.

We examined stool specimens for viral pathogens from 50 children referred to hospital due to acute gastroenteritis (AGE) resulting from consuming drinking water contaminated with sewage in a Finnish community using PCR methods. Rotavirus was detected in 33 (66%), human calicivirus in 31 (62%), and both in 40% of cases. Of the caliciviruses, 20/31 (65%) were noroviruses and 11 (35%) sapoviruses. Furthermore, Aichi virus was detected in 25 (50%), adenovirus in six (12%) and bocavirus in four (8%) cases. Campylobacter jejuni was present in 20 (61%) and Salmonella in four (12%) of the 33 stools cultured for bacteria. On a 20-point scale median severity score of AGE in the 28 hospitalized children was 17; the severity was similar regardless of viruses detected. Bloody diarrhoea occurred only when C. jejuni was present. To conclude, massive exposure to several AGE viruses caused mixed infections and severe AGE regardless of the aetiological agents.

The world is currently confronting the first influenza pandemic of the 21st century [caused by a novel pandemic influenza A (H1N1) virus]. Earlier pandemics have been characterized by age distributions that are distinct from those observed with seasonal influenza epidemics, with higher attack rates (and correspondingly increased proportionate or relative mortality) in younger individuals. While the genesis of protection against infection in older individuals during a pandemic is uncertain, differential vulnerability to infection by age has important implications for disease dynamics and control, and for choice of optimal vaccination strategies. Age-related vulnerability to infection may explain differences between school- and community-derived estimates of the reproductive number (R) for a newly emerged pandemic strain, and may also help explain the failure of a newly emerged influenza A (H1N1) virus strain to cause a pandemic in 1977. Age-related factors may also help explain variability in attack rates, and the size and impact of influenza epidemics across jurisdictions and between populations. In Canada, such effects have been observed in the apparently increased severity of outbreaks on Indigenous peoples' reserves. The implications of these patterns for vaccine allocation necessitate targeted research to understand age-related vulnerabilities early in an influenza pandemic.

The phage types and antimicrobial susceptibilities of 226 isolates of Salmonella enterica serovar Typhi from imported cases in Japan between 2001 and 2006 were investigated. Most (93·8%) had travelled to Asian countries, particularly South East Asia. Twenty-one phage types were identified with E1 (30·5%), UVS (15·9%) and B1 (9·3%) being the most common. The frequency of multidrug-resistant strains reached 37·0% in 2006 with phage types E1 and E9 predominating. Almost half (48·2%) of the isolates were resistant to nalidixic acid and two isolates displayed high-level fluoroquinolone resistance. Three mutations, two in gyrA and one in parC, were identified in both isolates.

Previous outbreaks of Pontiac fever have invariably been associated with water droplet spread of Legionella spp. In January 2007 three workers from a horticultural nursery were admitted to hospital with non-pneumonic legionellosis. Investigations showed that a working party of ten people had been exposed to aerosolized potting mix; nine of these workers met the case definition for Pontiac fever. The presence of genetically indistinguishable Legionella longbeachae serogroup 2 was demonstrated in clinical specimens from two hospitalized workers and in the potting mix to which they had been exposed. A further seven cases were diagnosed by serological tests. This is the first documented outbreak of Pontiac fever from L. longbeachae serogroup 2 confirmed from inhalation of potting mix. Pontiac fever is likely to be under-diagnosed. We advocate the introduction of an industry standard that ensures the use of face masks when handling potting mix and attaching masks and warning labels to potting mix bags sold to the public.

This study aimed to determine the relationship between hepatitis C virus (HCV) infection and ABO/Rhesus blood groups, age and sex. A total of 20 000 patients who came to donate blood in the blood bank of GSVM Medical College, Kanpur were enrolled in the study. Demographic data recorded for each patient included age, sex and blood group. Blood samples were tested for anti-HCV antibodies and ABO/Rhesus blood group antigen typing was performed. The overall positive rate of anti-HCV was 0·34%. We found that seropositivity for HCV increased with age. Anti-HCV antibodies were detected in 1/765 women (0·13%), compared to 67/19 235 men (0·35%). Seroprevalence of HCV was found to be higher in blood group O individuals (0·42%) and lowest in blood group AB individuals (0·04%). The results of this study demonstrate that that HCV infection may not be related to age and sex but the possible association of blood group antigens with HCV infection cannot be ruled out.

A total of 969 isolates of Campylobacter jejuni originating in the Preston, Lancashire postcode district over a 3-year period were characterized using multi-locus sequence typing. Recently developed statistical methods and a genetic model were used to investigate temporal, spatial, spatio-temporal and genetic variation in human C. jejuni infections. The analysis of the data showed statistically significant seasonal variation, spatial clustering, small-scale spatio-temporal clustering and spatio-temporal interaction in the overall pattern of incidence, and spatial segregation in cases classified according to their most likely species-of-origin.

One of the largest reported campylobacteriosis outbreaks in Canada occurred in June 2007 in British Columbia, associated with a mountain bike race that took place in muddy conditions. A retrospective cohort study was conducted and environmental samples were collected and tested. There were 537 racers included in the study and 225 racers (42%) reported diarrhoeal illness after the race. C. jejuni clinical isolates (n=14) were found to be identical by multi-locus sequence typing. Although univariate analysis suggested water consumption and mud exposure as significant risk factors, multivariate analysis revealed that on direct ingestion mud was significantly associated with illness (OR 4·08, 95% CI 2·03–8·21). Contaminated mud was thus the most likely source of Campylobacter infection. We identified other unpublished reports of outbreaks associated with bike races in rainy or muddy conditions; these underscore the importance of educating racers and raising public awareness of the risks of mud ingestion.

It has been suggested that the incidence of herpes zoster may increase due to lack of natural boosting under large-scale vaccination with the varicella vaccine. To study the possibility and magnitude of such negative consequences of mass vaccination, we built a mathematical model of varicella and zoster epidemiology in the Finnish population. The model was based on serological data on varicella infection, case-notification data on zoster, and new knowledge about close contacts relevant to transmission of infection. According to the analysis, a childhood programme against varicella will increase the incidence of zoster by one to more than two thirds in the next 50 years. This will be due to increase in case numbers in the ⩾35 years age groups. However, high vaccine coverage and a two-dose programme will be very effective in stopping varicella transmission in the population.

Profiles of varicella-zoster virus (VZV) seroprevalence have shown large variability in European countries in which vaccination has not been implemented. Differences in micro and macro population structures (e.g. household and municipality, respectively) may explain such variability, which is the focus of a population-based study of varicella in 12 000 children from 7800 French households in Corsica. The cumulative incidence was 89% at age 11 years, as the median age at infection was 5 years in first-born children, but decreased to 3·9 years in younger siblings. Hazard of infection in households increased as the first-born child initially enrolled in primary school. Age at infection was higher in less populated areas. Household attack rates increased with age (55% in <6 months, >90% in >3 years) and household secondary attack rate was ∼70%. Several levels of population structure independently affect age at varicella infection.

We analysed the serotypes and antibiotic susceptibility of 1560 human and 1505 non-human Salmonella isolated in New Zealand (NZ) between 2002 and 2007. The most common serotypes in humans were Salmonella enterica serovar Typhimurium, S. Enteritidis, S. Brandenburg and S. Infantis. Over the 6-year period human cases due to S. Agona and S. Enteritidis increased and cases due to S. Typhimurium decreased. The most common serotypes from non-human sources were S. Typhimurium, S. Brandenberg, S. Hindmarsh and S. Infantis, and there were no significant changes over time. More isolates were non-susceptible to streptomycin than to any other antibiotic. Almost all isolates were susceptible to ciprofloxacin and gentamicin. There were significant trends of increasing non-susceptibility to streptomycin and sulfonamides in isolates from human and non-human sources, while ampicillin, tetracycline and multidrug non-susceptibility also increased in human isolates. Despite these increases, rates of antibiotic non-susceptibility in Salmonella in NZ are still lower than in many international settings.

On 29 April 2009, an imported case of pandemic (H1N1) 2009 virus infection was detected in a London school. As further cases, pupils and staff members were identified, school closure and mass prophylaxis were implemented. An observational descriptive study was conducted to provide an insight into the clinical presentation and transmission dynamics in this setting. Between 15 April and 15 May 2009, 91 symptomatic cases were identified: 33 were confirmed positive for pandemic (H1N1) 2009 virus infection; 57 were tested negative; in one the results were unavailable. Transmission occurred first within the school, and subsequently outside. Attack rates were 2% in pupils (15% in the 11–12 years age group) and 17% in household contacts. The predominant symptoms were fever (97%), respiratory symptoms (91%), and sore throat (79%). Limited spread in the school may have been due to a combination of school closure and mass prophylaxis. However, transmission continued through household contacts to other schools.