This paper elaborates a concept of enrichment dynamics introduced in an earlier paper in which the author set out to find a labour saving technique for isolating salmonellac from sources other than faeces. Extensions to the concept are summarised in the Introduction. Explanations are given why a multiplicity of isolation procedures used in combination should normally yield more isolations than any one procedure alone.

Since a limit must always be set on the number of different media and procedures which can be used during routine examinations, a corresponding limit has also to be set on the combined efficiency of the procedures used. Not even a very laborious combination of methods can be expected to yield quite 100% of the isolations that are technically possible. When this rather unpalatable conclusion is accepted, a way is opened up for compromises between endeavour and reward, in terms of salmonella isolations. Judicious application of principles and methods discussed in these papers might be expected sometimes to lead to modifications in techniques which increase their efficiency, and in other cases to modifications which reduce labour without diminishing efficiency.

Naegleria fowleri, a free-living, thermophilic amoeba ubiquitous in the environment, causes primary amoebic meningoencephalitis (PAM), a rare but nearly always fatal disease of the central nervous system. While case reports of PAM have been documented worldwide, very few individuals have been diagnosed with PAM despite the vast number of people who have contact with fresh water where N. fowleri may be present. In the USA, 111 PAM case-patients have been prospectively diagnosed, reported, and verified by state health officials since 1962. Consistent with the literature, case reports reveal that N. fowleri infections occur primarily in previously healthy young males exposed to warm recreational waters, especially lakes and ponds, in warm-weather locations during summer months. The annual number of PAM case reports varied, but does not appear to be increasing over time. Because PAM is a rare disease, it is challenging to understand the environmental and host-specific factors associated with infection in order to develop science-based, risk reduction messages for swimmers.

As a major foodborne pathogen, Campylobacter jejuni receives much attention in quantitative risk assessment. To date, all dose–response assessments have been based on a single human feeding study which unfortunately provides incomplete and possibly biased information on the dose–response relation. An incident at a dairy farm, where several children from a school class became ill as a result of drinking raw milk contaminated with C. jejuni, appeared to show a very clear dose–response relation between the amount of milk consumed and the attack rate. This relation was very nearly exponentially shaped and, therefore, seemed to conflict with the rather slowly rising dose–response relation established in the feeding study. Here we show that both datasets can be reconciled when illness and infection are considered separately. This not only provides new information on the illness dose–response relation for Campylobacter, but also amends the infection dose–response relation because of their conditional dependence.

The prevalence of Escherichia coli O157 displays striking variability across the Scottish cattle population. On 78% of farms, in a cross-sectional survey of 952, no shedding of E. coli O157 was detected, but on a small proportion, ∼2%, very high prevalences of infection were found (with 90–100% of pats sampled being positive). We ask whether this variation arises from the inherent stochasticity in transmission dynamics or whether it is a signature of underlying heterogeneities in the cattle population. A novel approach is taken whereby the cross-sectional data are viewed as providing independent snapshots of a dynamic process. Using maximum-likelihood methods to fit time-dependent epidemiological models to the data we obtain estimates for the rates of immigration and transmission of E. coli O157 infection – parameters which have not been previously quantified in the literature. A comparison of alternative model fits reveals that the variation in the prevalence data is best explained when a proportion of the cattle are assumed to transmit infection at much higher levels than the rest – the so-called super-shedders. Analysis of a second dataset, comprising samples taken from 32 farms at monthly intervals over a period of 1 year, additionally yields an estimate for the rate of recovery from infection. The pattern of prevalence displayed in the second dataset also strongly supports the super-shedder hypothesis.

Clostridium perfringens isolates are currently classified into one of five biotypes on the basis of the differential production of α-, β-, ε- and ι-toxins. Different biotypes are associated with different diseases of man and animals. In this study a multiple PCR assay was developed to detect the genes encoding these toxins. In addition, detection of the genes encoding the C. perfringens enterotoxin and β2-toxin allowed subtyping of the bacteria. C. perfringens isolates taken from a variety of animals, including foals, piglets or lambs, were genotyped using this assay. Most of the isolates were found to be genotype A and the gene encoding β-toxin was present in 50% of the isolates genotyped. A significant association between C. perfringens possessing the β2-toxin gene and diarrhoea in piglets was identified, suggesting that β2-toxin may play a key role in the pathogenesis of the disease.

Minced beef samples inoculated with Escherichia coli O157 were cultured in buffered peptone water supplemented with vancomycin, cefsulodin and cefixime (BPW-VCC) and subcultured to cefixime tellurite sorbitol MacConkey (CT-SMAC) agar both directly and after immunomagnetic separation (IMS) of the organism with magnetic beads coated with an antibody against E. coli O157 (Dynabeads anti-E. coli 0157, Dynal, Oslo). E. coli O157 was recovered from initial inocula of 200 organisms/g by direct subculture and 2 organisms/g by IMS. Twelve strains of E. coli 0157 of different combinations of phage type, H antigen and toxin genotype were all recovered from initial inocula of two organisms/g by IMS. Nonspecific binding of other organisms to the magnetic beads could be reduced by washing of the beads in PBS with Tween-20 0·002–0.005% E. coli O157 was not bound by magnetic coated with an unrelated antibody.

During investigation of a dairy herd that was possibly linked to a small outbreak of infection with E. coli O157, the organism was isolated from 2 of 279 forestream milk samples from individual cattle; both isolates were made only by the IMS technique. IMS is rapid, technically simple, and a specific method for isolation of E. coli O157 and will be useful in epidemiological studies.

Since 1996 Salmonella Typhimurium DT104 salmonellosis has increased in The Netherlands. This prompted a case-control study of risk factors for salmonellosis to inform transmission routes for this phage type. Cases were laboratory-confirmed patients with a Salmonella infection and controls were selected from population registries by frequency matching for age, sex, degree of urbanization and season. Cases and controls received a questionnaire on risk factors. Of the 1171 cases, 573 (49%) responded: 245 S. Enteritidis and 232 S. Typhimurium cases (both DT104 and non-DT104), of which 58 were DT104. Of the 10250 controls, 3409 (33%) responded. Use of H2 antagonists [odds ratio (OR) 4·4, 95% CI 1·6–12·2] and proton pump inhibitors (OR 4·2, 95% CI 2·2–7·9), consumption of raw eggs (OR 3·1, 95% CI 1·3–7·4) and products containing raw eggs (OR 1·8, 95% CI 1·1–3·0) were associated with endemic S. Enteritidis infection. Risk factors for endemic S. Typhimurium infection were use of proton pump inhibitors (OR 8·3, 95% CI 4·3–15·9), occupational exposure to raw meat (OR 3·0, 95% CI 1·1–7·9), playing in a sandbox (for children aged 4–12 years) (OR 2·4, 95% CI 1·6–3·7), consumption of undercooked meat (OR 2·2, 95% CI 1·1–4·1) and use of antibiotics (OR 1·9, 95% CI 1·0–3·4). Use of proton pump inhibitors (OR 11·2, 95% CI 3·9–31·9) and playing in a sandbox (OR 4·4, 95% CI 1·8–10·7) were the only risk factors for S. Typhimurium DT104 salmonellosis. This study confirms known risk factors for salmonellosis. However, playing in a sandbox was a predominant new risk factor for S. Typhimurium salmonellosis in children [population attributable risk (PAR) 14%], and especially for S. Typhimurium DT104 (PAR 32%).

Knowledge of hepatitis B and C prevalence, and numbers infected, are important for planning responses. Published HBsAg and anti-HCV prevalences for the 20 WHO European Region countries outside the EU/EFTA were extracted, to complement published data for the EU/EFTA. The general population prevalence of HBsAg (median 3·8%, mean 5·0%, seven countries) ranged from 1·3% (Ukraine) to 13% (Uzbekistan), and anti-HCV (median 2·3%, mean 3·8%, 10 countries) from 0·5% (Serbia, Tajikistan) to 13% (Uzbekistan). People who inject drugs had the highest prevalence of both infections (HBsAg: median 6·8%, mean 8·2%, 13 countries; anti-HCV: median 46%, mean 46%, 17 countries), and prevalence was also elevated in men who have sex with men and sex workers. Simple estimates indicated 13·3 million (1·8%) adults have HBsAg and 15·0 million (2·0%) HCV RNA in the WHO European Region; prevalences were higher outside the EU/EFTA countries. Efforts to prevent, diagnose, and treat these infections need to be maintained and improved.

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The aetiology of sporadic campylobacter infection was investigated by means of a multicentre case-control study. During the course of the study 598 cases and their controls were interviewed.

Conditional logistic regressional analysis of the data collected showed that occupational exposure to raw meat (odds ratio [OR] 9·37; 95 % confidence intervals [CI] 2·03, 43·3), having a household with a pet with diarrhoea (OR 2·39; CI 1·09. 5·25), and ingesting untreated water from lakes, rivers and streams (OR 4·16; CI 1·45. 11·9) were significant independent risk factors for becoming ill with campylobacter. Handling any whole chicken in the domestic kitchen that had been bought raw with giblets, or eating any dish cooked from chicken of this type in the home (OR 0·41–0·44; CI 0·24, 0·79) and occupational contact with livestock or their faeces (OR 0·44; CI 0·21, 0·92) were significantly associated with a decrease in the risk of becoming ill with campylobacter.

A serological study of cytomegalovirus infection in London shows it to be prevalent. Under 5 years of age only 4% of children have antibodies, but this increases to 15% by 10 years of age and 21% by 15 years. The maximum incidence of 54% is reached by 25–35 years, and this is maintained in the older age groups of the population. In two mixed day schools the incidence of infection was significantly lower than in a boarding school, suggesting that close prolonged contact is required for spread of infection.

Different strains of cytomegalovirus possess common group-specific complement-fixing antigens.

It is suggested that clinical disease caused by cytomegaloviruses is more frequent and more varied than previously believed, although diagnosis may be difficult without virological help.

Self-report of polysaccharide pneumococcal vaccination is not thought reliable because of the increased risk of adverse events from inadvertent re-vaccination in elderly people. Some studies suggest a high sensitivity of self-report and hence a low risk of adverse events if vaccination is administered when medical records are unavailable. Self-report of pneumococcal and influenza vaccination in a sample of >64-year-olds in the United Kingdom was compared with information in their medical records. Self-report of pneumococcal vaccination, in contrast to some of the other studies had a low sensitivity. The findings here support the need for accurate knowledge of prior vaccine status before offering the polysaccharide pneumococcal vaccine. The study also confirms that self-report of influenza vaccination could be relied upon if rapid knowledge of uptake is required.

Data on the pre-vaccination patterns of infection for measles, mumps and rubella are collated from a number of European countries in order to compare the epidemiology of the three viruses. Key epidemiological parameters, such as the age-specific force of infection and the basic reproduction number (R0) are estimated from case notification or serological data using standard techniques. A method is described to compare force of infection estimates derived from serological data. Analysis suggests that the pre-vaccination patterns of measles and mumps infection in the different countries were similar. In contrast, the epidemiology of rubella was highly variable between countries. This suggests that it may be acceptable to use parameter values estimated from other countries to model measles and mumps transmission, but that this approach to modelling rubella transmission requires more caution. Estimates of R0 depend on underlying mixing assumptions. Constraints were placed on R0 estimates by utilising knowledge of likely mixing patterns. The estimates for R0 were highest for measles, intermediate for mumps, and generally lowest for rubella. Analysis of within- and between-age-group transmission rates suggested that mumps transmission tends to be more concentrated within young children than the other two viruses. The implications for the design of immunization programmes are that mumps may be the easiest to control via infant immunization since it is predominantly transmitted between the very young and the variability in rubella epidemiology requires that careful consideration of the possible effects of vaccination options should be made using local data when planning rubella immunization programmes.

Clinical information was collected on 722 cases of Listeria monocytogenes infections in humans occurring in Britain between 1967 and 1985: 248 cases (34%) were associated with pregnancy (maternal, foetal, and neonatal), and comprised 9 cases (4%) of maternal bacteraemia without infection of the foetus; 42 cases (19%) of intra-uterine deaths; 118 cases (54%) of neonatal infection diagnosed within 2 days post-partum; and 50 cases (23%) of neonatal infection diagnosed as ill after 2 days post-partum. An overall mortality of 50% was recorded.

The cases unassociated with pregnancy are described elsewhere (see accompanying paper).

Campylobacter spp. is a widespread and important cause of human illness worldwide. Disease is frequently associated with foodborne transmission, but other routes of exposure, such as direct contact with live animals and person-to-person transmission, are also recognized. Identifying the most important sources of human disease is essential for prioritizing food safety interventions and setting public health goals. Numerous case-control studies of sporadic infections of campylobacteriosis have been published. These studies investigated a variety of potential risk factors for disease, often using different methodologies and settings. Systematic reviews (SRs) consist of a formal process for literature review focused on a specific research question, and include the identification of relevant literature, quality assessment of relevant studies, summarization or statistical analysis of data, and conclusions. With the objective of identifying the most important risk factors for human sporadic campylobacteriosis, we performed a SR of case-control studies of human sporadic cases and a meta-analysis of the obtained results. A combined SR focusing on Salmonella and Campylobacter studies was performed and the results analysed separately. From 1295 identified references, 131 passed the relevance screening, 73 passed the quality assessment stage, and data was extracted from 72 studies. Of these, 38 focused on campylobacteriosis. Information on exposures of cases and controls, and estimated odds ratios for investigated risk factors were collected and analysed. In the meta-analysis, heterogeneity between the studies and possible sources of bias were investigated, and pooled odds ratios for identified risk factors were estimated. Results suggest that travelling abroad, eating undercooked chicken, environmental sources, and direct contact with farm animals were significant risk factors for campylobacteriosis. Sub-analyses by geographical region, age group, and study period were performed, and differences were discussed.

We report here a new and critical determinant of the effectiveness of hand hygiene procedures, namely the amount of residual moisture left on the hands after washing and drying. When samples of skin, food and utilities were touched with wet, undried hands, microbial numbers in the order of 68000, 31000 and 1900 respectively translocated to these representative surfaces. Bacterial numbers translocating on touch contact decreased progressively as drying with an air or cloth towel system removed residual moisture from the hands. A 10 s cloth towel–20 s air towel protocol reduced the bacterial numbers translocating to skin, food and utilities on touch contact to 140, 655 and 28 respectively and achieved a 99·8, 94 and 99% reduction in the level of bacterial translocation associated with wet hands. Careful hand drying is a critical factor determining the level of touch-contact-associated bacterial transfer after hand washing and its recognition could make a significant contribution towards improving handcare practices in clinical and public health sectors.

In 2011, a novel orthobunyavirus of the Simbu serogroup, the Schmallenberg virus (SBV), was discovered using a metagenomic approach. SBV caused a large epidemic in Europe in ruminants. As with related viruses such as Akabane virus, it appears to be transmitted by biting midges. Transplacental infection often results in the birth of malformed calves, lambs and goat kids. In more than 5000 farms in Germany, The Netherlands, Belgium, France, UK, Italy, Spain, Luxembourg, Denmark and Switzerland acute infections of adult ruminants or malformed SBV-positive offspring were detected, and high seroprevalences were seen in adult ruminants in the core regions in The Netherlands, Germany and Belgium. The discovery of SBV, the spread of the epidemic, the role of vectors, the impact on livestock, public health issues, SBV diagnosis and measures taken are described in this review. Lessons to be learned from the Schmallenberg virus epidemic and the consequences for future outbreaks are discussed.

The infectivity of pathogenic microorganisms is a key factor in the transmission of an infectious disease in a susceptible population. Microbial infectivity is generally estimated from dose–response studies in human volunteers. This can only be done with mildly pathogenic organisms. Here a hierarchical Beta-Poisson dose–response model is developed utilizing data from human outbreaks. On the lowest level each outbreak is modelled separately and these are then combined at a second level to produce a group dose–response relation. The distribution of foodborne pathogens often shows strong heterogeneity and this is incorporated by introducing an additional parameter to the dose–response model, accounting for the degree of overdispersion relative to Poisson distribution. It was found that heterogeneity considerably influences the shape of the dose–response relationship and increases uncertainty in predicted risk. This uncertainty is greater than previously reported surrogate and outbreak models using a single level of analysis. Monte Carlo parameter samples (α, β of the Beta-Poisson model) can be readily incorporated in risk assessment models built using tools such as S-plus and @ Risk.

In all temperate countries campylobacter infection in humans follows a striking seasonal pattern, but little attention has been given to exploring the epidemiological explanations. In order to better characterize the seasonal patterns, data from nine European countries and New Zealand have been examined. Several European countries with weekly data available showed remarkably consistent seasonal patterns from year to year, with peaks in week 22 in Wales, week 26 in Scotland, week 32 in Denmark, week 30 in Finland and week 33 in Sweden. In Europe, the seasonal peak was most prominent in Finland and least prominent in Scotland and Austria. In New Zealand the seasonality was less consistent since the peak was more prolonged. Possible explanations for the seasonal peaks are discussed. Research into the causes of campylobacter seasonality should help considerably in elucidating the sources of human infection.

To determine methicillin-resistant Staphylococcus aureus (MRSA) carriage in poultry and slaughterhouse personnel, 40 Dutch broiler flocks, in six slaughterhouses and 466 personnel were sampled. Of the employees, 26 were positive (5·6%), indicating a higher risk of exposure when compared to the general Dutch population (0·1%). This risk was significantly higher for personnel having contact with live animals (5·2%) – especially hanging broilers on the slaughterline (20·0%) – than for all other personnel (1·9%). Conventional electric stunning conferred a significantly higher risk of MRSA carriage for employees than CO2 stunning (9·7% vs. 2·0%). A total of 405 broilers were sampled upon their arrival at the slaughterhouse, of which 6·9% were positive. These broilers originated from 40 Dutch slaughter flocks of which 35·0% were positive. MRSA contamination in the different compartments of slaughterhouses increased during the production day, from 8% to 35%. Of the 119 MRSA isolates, predominantly livestock-associated MRSA ST398 was found, although 27·7% belonged to ST9 (spa type t1430). There is an increased risk of MRSA carriage in personnel working at broiler slaughterhouses, particularly those having contact with live animals.

The response to the novel coronavirus outbreak in China suggests that many of the lessons from the 2003 SARS epidemic have been implemented and the response improved as a consequence. Nevertheless some questions remain and not all lessons have been successful. The national and international response demonstrates the complex link between public health, science and politics when an outbreak threatens to impact on global economies and reputations. The unprecedented measures implemented in China are a bold attempt to control the outbreak – we need to understand their effectiveness to balance costs and benefits for similar events in the future.