A study was designed to investigate management factors that might influence the shedding of verocytotoxin-producing Escherichia coli (VTEC) O157 by beef cows in Scotland, where there is a particularly high rate of human infection. Thirty-two herds were visited at least monthly over approximately 1 year for collection of fresh faecal pat samples and information on management factors. The faecal pat samples were tested for VTEC O157 by established culture and immunomagnetic separation methods. Questionnaires were completed at the monthly visits to record management factors. Data were analysed using both univariate and multi-factor (GLMM) analysis. Changes in the number of cows in a group, dogs, wild geese, housing, and the feeding of draff (distillers' grains) were statistically significant as risk factors. The event of calving appeared to reduce the likelihood of shedding. Any effects of weaning or turnout were not statistically significant. It appears that the rate of shedding of VTEC O157 is influenced by several factors but possibly the most important of these are the circumstances of animals being housed, or, when outside, the presence of wild geese.

The incidence of dengue infection, a vector-borne disease transmitted by the mosquito Aedes aegypti, shows clear dependence on seasonal variation. Based on the quantification method that furnishes the size of the A. aegypti population in terms of the estimated entomological parameters for different temperatures, we assessed the risk of dengue outbreaks. The persistence and severity of epidemics can be assessed by the basic reproduction number R0, which varies with temperature. The expression for R0 obtained from ‘true’ and ‘pseudo’ mass action laws for dengue infection is discussed.

Chickens given orally at 4 days of age a smooth spectinomycin resistant mutant (Spcr) of Salmonella typhimurium strain F98 excreted the organism in their faeces for approximately 4 weeks. Following oral administration of a nalidixic acid resistant (Nalr) mutant of the same strain 4 weeks later when later when the chickens had virtually cleared themselves of the first infection, these chickens excreted far fewer salmonella organisms and for a shorter time than did a previously uninfected control group of chickens which were infected at the same time with the Nalr mutant. Chickens inoculated intramuscularly at 4 days developed a similar immunity to challenge and also excreted the immunizing strain in their faeces. In contrast intramuscular inoculation or incorporation into the food of formalin-killed S. typhimurium organisms had little lasting effect on the faecal excretion of the challenge strain. Two attenuated mutants of strain F98 Nalr were produced: one was a rough strain produced by lytic bacteriophage and the other was an aro A auxotrophic mutant which had been cured of the 85 kilobase–pair virulence–associated plasmid. These mutants were avirulent for chickens, mice, calves and man and when ingested by human volunteers did not persist in the faeces. When inoculated intramuscularly into chickens they produced an early reduction in faecal excretion of the challenge strain (Spcr) which was not maintained. Oral administration of both strains produced reductions in faecal excretion of the challenge strain. This was much more noticeable with the rough strain which was itself excreted for a much longer period than the parent strain.

A longitudinal study of the effect of time spent in lairage on salmonellas in the caecum and on the skin surface of 450 slaughter pigs from a single producer was conducted. Pigs were tested in 6 groups at 2 abattoirs, with one-third of a group being slaughtered after 18 h, one-third after 42 h and one-third after 66 h spent in lairage. The salmonella isolation rate from caeca and carcass surfaces increased significantly with increasing time spent in lairage. Salmonellas were isolated from the caeca of 18·5% of pigs held less than 24 h in lairage, 24·1% of pigs held a further 24 h and 47·7% of pigs held for 66 h in lairage before slaughter. The salmonella isolation rates from carcasses were 9·3%, 12·8% and 27·3% for the same groups. Thirteen salmonella serotypes were isolated from the caecal contents and carcasses over the 6 weeks of the trial. One abattoir had a higher salmonella isolation rate from pigs than the other and this was probably related to lairage management. It appeared that lairage is an important factor in the manipulation of the salmonella contamination of pig carcasses.

Data relating to 3313 adenovirus isolates from patients in Greater Manchester, UK between 1982 and 1996 were analysed using χ2 tests and 95% confidence intervals. Of the 3098 isolates that were typed, 18·6% were serotype 2, 14·9% serotype 3, 12·1% serotype 1 and 10·9% serotype 41. There was evidence of a seasonal occurrence of serotype 7 (March–August), serotype 2 (January–April), serotype 4 (June–August) and subgenus F (September–November). Children less than 5 years old were the most common group of patients with adenovirus infection (61·3%) compared to 24·2% for adults and only 5·6% for school children (5–15 years). Gastric symptoms were the most common amongst infants (47·6%) followed by respiratory (27·5%) and general symptoms (12·9%). In adults, the overwhelming clinical condition was conjunctivitis (88·9%). Despite the traditional association with adenoviruses, remarkably few cases of pharyngoconjunctival fever were recorded (1·7%).

In this study we have evaluated the ability of three typing methods, pulsed field gel electrophoresis (PFGE), phage-typing and ribotyping, to discriminate not only between strains of differing serotypes but also between strains within a single serotype, heat stable serotype 2 (HS2). Forty-five isolates derived from cases of campylobacter enteritis occurring in the Cardiff area were examined. These included 18, mostly HS2, strains associated with an outbreak. The typing results for these and a further 39 epidemiologically unrelated strains of serotype HS2 were compared. This is the first report documenting the use of PFGE in an epidemiological investigation of Campylobacter jejuni in the UK. The results presented suggest that this technique is the most discriminatory of the three subtvping methods examined.

Mycobacterium avium subspecies paratuberculosis is the causative agent of Johne's disease, a chronic enteritis in ruminants including cattle, sheep, goats, and farmed deer. Recently, this bacterium has received an increasingly wide interest because of a rapidly growing body of scientific evidence which suggests that human infection with this microorganism may be causing some, and possibly all, cases of Crohn's disease. Recent studies have shown that a high percentage of people with Crohn's disease are infected with M. avium subsp. paratuberculosis; whether the association of this bacterium and Crohn's disease is causal or coincidental is not known. Crohn's disease is a gastrointestinal disease in humans with similar histopathological findings to those observed in the paucibacillary form of Johne's disease in cattle. The search for risk factors in Crohn's disease has been frustrating. However, epidemiologists have gathered enough information that points to an association between M. avium subsp. paratuberculosis and Crohn's disease. This paper reviews epidemiological models of disease causation, the major philosophical doctrines about causation, the established epidemiological criteria for causation, and the currently known epidemiological evidence of M. avium subsp. paratuberculosis as a possible cause of Crohn's disease.

Differentiation of Salmonella enteritidis by plasmid profile typing has been compared to differentiation by phage typing. Examination of the type strains of the 27 S. enteritidis phage types showed that only 11 profile patterns could be identified. Moreover, two profile patterns were found in 15 of the type strains, including those of the two most common phage types in Britain, types 4 and 8. On this basis, plasmid profile typing is not as sensitive as phage typing for the primary subdivision of S. enteritidis.

When differentiation of 534 strains of the 27 phage types was attempted using plasmid profiles, variation in pattern suitable for epidemiologieal subdivision was found in 13 phage types and there were 9 profile patterns in strains of phage type 4. Plasmid profile typing can, therefore, be regarded as an effective adjunct to phage typing for the subdivision of S. enteritidis

Foodborne illness is a major cause of morbidity and loss of productivity in developed nations. Although low socioeconomic status (SES) is generally associated with negative health outcomes, its impact on foodborne illness is poorly understood. We conducted a systematic review to examine the association between SES and laboratory-confirmed illness caused by eight important foodborne pathogens. We completed this systematic review using PubMed for all papers published between 1 January 1980 and 1 January 2013 that measured the association between foodborne illness and SES in highly developed countries and identified 16 studies covering four pathogens. The effect of SES varied across pathogens: the majority of identified studies for Campylobacter, salmonellosis, and E. coli infection showed an association between high SES and illness. The single study of listeriosis showed illness was associated with low SES. A reporting bias by SES could not be excluded. SES should be considered when targeting consumer-level public health interventions for foodborne pathogens.

Case reports have indicated transmission of Staphylococcus aureus between humans and pets. We investigated associations between level of contact between dog and owner, and S. aureus colonization. In a cross-sectional study, nasal carriage and antibiotic susceptibility of S. aureus was determined for 830 dogs and 736 owners. Relatedness of isolates was investigated using antibiograms and pulsed-field gel electrophoresis (PFGE). Associations between carriage and demographics or amount of contact between owners and dogs were documented. S. aureus was isolated in 24% of humans and 8·8% of dogs. Antibiotic resistance was significantly more common in canine isolates. Of 17 owner/dog colonized pairs, six were indistinguishable by PFGE. Colonization of dogs was not associated with close human contact, but was strongly associated with health-care occupations (OR 3·29, 95% CI 1·49–7·26, P=0·002). In outbreak situations health-care workers' pets should be considered as a source of S. aureus. High rates of resistance indicate increased monitoring of antibiotic use in veterinary practice is needed.

The global incidence of Shigella infection has been estimated at 80–165 million episodes annually, with 99% of episodes occurring in the developing world. To identify contemporary gaps in the understanding of the global epidemiology of shigellosis, we conducted a review of the English-language scientific literature from 1984 to 2005, restricting the search to low and medium human development countries. Our review yielded 11 population-based studies of Shigella burden from seven countries. No population-based studies have been conducted in sub-Saharan Africa or in low human development countries. In studies done in all age groups, Shigella incidence varied from 0·6 to 107 episodes/1000 person-years. S. flexneri was the most commonly detected subgroup in the majority of studies. Case-fatality rates ranged from 0% to 2·6% in population-based studies and from 0% to 21% in facility-based studies. This review highlights the large gaps in data on the burden of Shigella infections for low human development index countries and, more specifically, for sub-Saharan Africa.

Global Health Security Index (GHSI) and Joint External Evaluation (JEE) are two well-known health security and related capability indices. We hypothesised that countries with higher GHSI or JEE scores would have detected their first COVID-19 case earlier, and would experience lower mortality outcome compared to countries with lower scores. We evaluated the effectiveness of GHSI and JEE in predicting countries' COVID-19 detection response times and mortality outcome (deaths/million). We used two different outcomes for the evaluation: (i) detection response time, the duration of time to the first confirmed case detection (from 31st December 2019 to 20th February 2020 when every country's first case was linked to travel from China) and (ii) mortality outcome (deaths/million) until 11th March and 1st July 2020, respectively. We interpreted the detection response time alongside previously published relative risk of the importation of COVID-19 cases from China. We performed multiple linear regression and negative binomial regression analysis to evaluate how these indices predicted the actual outcome. The two indices, GHSI and JEE were strongly correlated (r = 0.82), indicating a good agreement between them. However, both GHSI (r = 0.31) and JEE (r = 0.37) had a poor correlation with countries' COVID-19–related mortality outcome. Higher risk of importation of COVID-19 from China for a given country was negatively correlated with the time taken to detect the first case in that country (adjusted R2 = 0.63–0.66), while the GHSI and JEE had minimal predictive value. In the negative binomial regression model, countries' mortality outcome was strongly predicted by the percentage of the population aged 65 and above (incidence rate ratio (IRR): 1.10 (95% confidence interval (CI): 1.01–1.21) while overall GHSI score (IRR: 1.01 (95% CI: 0.98–1.01)) and JEE (IRR: 0.99 (95% CI: 0.96–1.02)) were not significant predictors. GHSI and JEE had lower predictive value for detection response time and mortality outcome due to COVID-19. We suggest introduction of a population healthiness parameter, to address demographic and comorbidity vulnerabilities, and reappraisal of the ranking system and methods used to obtain the index based on experience gained from this pandemic.

Although pneumonia is a leading cause of death from infectious disease worldwide, comprehensive information about its causes and incidence in low- and middle-income countries is lacking. Active surveillance of hospitalized patients with pneumonia is ongoing in Thailand. Consenting patients are tested for seven bacterial and 14 viral respiratory pathogens by PCR and viral culture on nasopharyngeal swab specimens, serology on acute/convalescent sera, sputum smears and antigen detection tests on urine. Between September 2003 and December 2005, there were 1730 episodes of radiographically confirmed pneumonia (34·6% in children aged <5 years); 66 patients (3·8%) died. A recognized pathogen was identified in 42·5% of episodes. Respiratory syncytial virus (RSV) infection was associated with 16·7% of all pneumonias, 41·2% in children. The viral pathogen with the highest incidence in children aged <5 years was RSV (417·1/100 000 per year) and in persons aged ⩾50 years, influenza virus A (38·8/100 000 per year). These data can help guide health policy towards effective prevention strategies.

Salmonella Braenderup is an uncommon serotype in the United States. In July 2004, a multistate outbreak of Salmonella Braenderup diarrhoeal infections occurred, with 125 clinical isolates identified. To investigate, we conducted a case-control study, enrolling 32 cases and 63 matched controls. Cheese, lettuce and tomato eaten at restaurants all appeared to be associated with illness. To further define specific exposures, we conducted a second study and asked managers of restaurants patronized by patients and controls about cheese, lettuce and tomato varieties used in dishes their patrons reported consuming. This information was obtained for 27 cases and 29 controls. Roma tomatoes were the only exposure significantly associated with illness (odds ratio 4·3, 95% confidence interval 1·2–15·9). Roma tomatoes from two restaurants were traced back to a single tomato packing house. The methods used in this field investigation to define specific exposures may be useful for other foodborne outbreaks.

The ongoing worldwide spread of the H5N1 influenza virus in birds has increased concerns of a new human influenza pandemic and a number of surveillance initiatives are planned, or are in place, to monitor the impact of a pandemic in near real-time. Using epidemiological data collected during the early stages of an outbreak, we show how the timing of the maximum prevalence of the pandemic wave, along with its amplitude and duration, might be predicted by fitting a mass-action epidemic model to the surveillance data by standard regression analysis. This method is validated by applying the model to routine data collected in the United Kingdom during the different waves of the previous three pandemics. The success of the method in forecasting historical prevalence suggests that such outbreaks conform reasonably well to the theoretical model, a factor which may be exploited in a future pandemic to update ongoing planning and response.

1. The most virulent strains of Salmonella typhi are those that develop both the Vi and O antigens in maximum quantities.

2. The Vi antigen is not a particularly toxic substance; it is less toxic for the mouse than the O antigen.

3. The main biological function of the Vi antigen is to protect the O antigen against the action of the natural or immune O antibody, thereby protecting the bacterial cell against phagocytosis and the bactericidal action of the serum.

4. The relative virulence for mice of freshly isolated strains of Salmonella typhi reflects their virulence for man.

The prevalence and risk factors associated with livestock-associated MRSA (LA-MRSA) carriage was examined in Danish and Belgian veterinarians. The MRSA and LA-MRSA carriage rates were 9·5% (95% CI 5·3–15·6) and 7·5% (95% CI 3·8–13·1) for MRSA and LA-MRSA, respectively, in Belgium and 1·4% (95% CI: 0·17–5·05) in Denmark (all Danish MRSA isolates belonged to the LA-MRSA genotype). All LA-MRSA isolates were resistant to tetracycline and 53·4% (7/13) showed a multi-resistant phenotype. LA-MRSA was significantly associated with veterinarians in contact with livestock (P=0·046). In the multivariable analysis, working with small animals in a veterinary clinic seems to be negatively associated (OR 0·15, 95% CI 0–1·0, P=0·05) and a strong direct association was found for LA-MRSA acquisition and exposure to live pigs (OR 12·1, 95% CI 1·6–548·5, P=0·01). Since carriage of MRSA ST398 may increase the risk of complications during hospitalization, our results underline that preventive measures may need to be developed for veterinary professionals, particularly for livestock veterinarians.

1. The characters of twenty-seven strains isolated from sheep in New Zealand and Australia were examined and compared with those of representative strains of Brucella abortus, Br. suis and Br. melitensis.

2. These strains could be classified in the brucella genus on the basis of cell morphology and staining, colonial morphology, cultural characteristics, biochemical properties, pathogenicity for laboratory animals and association with genital disease in the natural host.

3. The ovine strains have never been observed in other than the non-smooth phase. Consequently, these organisms lack the specific surface antigens of smooth brucellae but are antigenically closely related to the non-smooth variants of other brucella species. Three antigenic factors were identified and their presence confirmed in all twenty-seven ovine strains.

4. The N.Z. and Australian ovine strains appear sufficiently stable and distinguishable from other established groups of the brucella genus in a number of independently variable characters to justify their constituting either a new species, Brucella ovis, or a new variety, Brucella brucei var. ovis australasiae. The author wishes to thank Prof. W. I. B. Beveridge for his continued interest and for providing accommodation and facilities.

Livestock feed is susceptible to contamination from wildlife excreta during on farm storage. Pathogens associated with diseases such as paratuberculosis, salmonella and cryptosporidiosis are present in wild rodent and bird excreta. Feed stores on four farms in the east of Scotland were monitored monthly over the winter of 1998/9 to quantify the levels of wildlife faecal contamination. A mean of 79·9 rodent (95% confidence interval: 37·5–165·9) and 24·9 (14·3–41·7) bird faeces were deposited per m2 of stored feed per month. It was estimated that individual cattle and sheep could encounter 1626 and 814 wildlife faeces over the winter.

A model based on the numbers of infected faeces consumed per annum was used to estimate ‘infectious probabilities’ (Pinf) required to account for the reported prevalence of paratuberculosis, salmonella and cryptosporidiosis in sheep and cattle in the east of Scotland in 1998. Based on empirical data for input variables [the number of faeces encountered (Fe), the number ingested (Fi) and the prevalence of infection in wildlife species (Ip)], Pinf estimates ranged from 1·6×10−8 for cryptosporidiosis in sheep to 8·2×10−6 for paratuberculosis in cattle. The model suggested that ingestion of feed contaminated by wildlife faeces could account for the prevalence of all three diseases. Wildlife faecal contamination of stored feed should be given serious consideration as a potential source of infection to livestock.

Large-scale population-based studies have reported a significant increase in invasive pneumococcal disease (IPD) in those with underlying haematological or solid-organ malignancy, but limited condition-specific data are available on rates of IPD in the adult population. A retrospective chart review of all patients with IPD (identified prospectively) in the province of Alberta, Canada (population ~3·3 million) was conducted from 2000 to 2004 to study the epidemiology of IPD. Rates of IPD in patients with various haematological and solid-organ malignancies were determined by obtaining the number of these patients at risk from the provincial cancer registry. Compared to the attack rate of IPD in the adult population aged ⩾18 years (11·0 cases/100 000 per year, 95% CI 10·44–11·65), there were significantly increased rates of IPD in those with lung cancer (143·6 cases/100 000 per year, OR 13·4, 95% CI 9·3–19·4, P<0·001) and multiple myeloma (673·9 cases/100 000 per year, OR 62·8, 95% CI 39·6–99·8, P<0·001). More modestly increased rates of IPD were found in those with chronic lymphocytic leukaemia, acute myeloid leukaemia, acute lymphoblastic leukaemia, and Hodgkin's and non-Hodgkin's lymphoma. There was an increased prevalence of serotype 6A in those with these underlying malignancies, but no other serotypes predominated. Fifty-three percent (48/83) of cases were caused by serotypes in the investigational 13-valent pneumococcal conjugate vaccine (PCV13), and 57/83 (69%) of the cases were caused by serotypes in the 23-valent pneumococcal polysaccharide vaccine (PPV23). The incidence of IPD in adults with certain haematological and solid-organ malignancies is significantly greater than the overall adult population. Such patients should be routinely given pneumococcal polysaccharide vaccine; this population could also be targeted for an expanded valency conjugate vaccine.