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.

Safe drinking water and hygiene are essential to reducing Kenya's diarrhoeal disease burden. A school-based safe water and hygiene intervention in Kenya was evaluated to assess its impact on students' knowledge and parents' adoption of safe water and hygiene practices. We surveyed 390 students from nine schools and their parents at baseline and conducted a final evaluation of 363 students and their parents. From baseline to final evaluation, improvement was seen in students' knowledge of correct water treatment procedure (21–65%, P<0·01) and knowing when to wash their hands. At final evaluation, 14% of parents reported currently treating their water, compared with 6% at baseline (P<0·01). From 2004 to 2005, school absenteeism in the September–November term decreased in nine project schools by 35% and increased in nine neighbouring comparison schools by 5%. This novel programme shows promise for reducing school absenteeism and promoting water and hygiene interventions in the home.

1. An investigation of measles was made in Nigeria as part of a longitudinal study of 405 village children, supplemented by observations on 1,283 children admitted to a Mission Hospital with the disease.

2. Measles was found to be the most serious of the acute infectious diseases of Nigerian children. During the Imesi village study measles played a major part in the death of 15, or 7% of the 222 children who were seen with measles. The overall case mortality in Nigeria is believed to be in the region of 5%. For children admitted to hospital with the complications of measles, a mortality in excess of 20% is not infrequent. This contrasts with the present situation in Northern Europe and America, where measles is of relatively minor public health importance.

3. Bronchopneumonia was present in nearly half the children needing admission to hospital. Of those with bronchopneumonia, 28% died.

4. Diarrhoea occurred in all stages of the disease, but was most common and severe during and following the period of desquamation. Treatment by parenteral fluid to combat dehydration was required in 55% of children admitted with this complication.

5. Extensive loss of weight was associated with the disease in the majority of children. In the village study nearly one child in four lost 10% of his former weight. The mean time taken to recover former weight was 7·2 weeks.

6. Children frequently developed marasmus and kwashiorkor after an attack of measles.

7. Striking appearances were observed in the rash and subsequently in the skin. In some children the rash darkened in colour in the manner described by Rhazes and other early writers. Extensive desquamation often appeared after the rash. The desquamation was most severe when the rash darkened.

8. The picture of measles in this study resembles descriptions of the disease to be found in the older literature. Accounts of the incidence and severity of bronchopneumonia, laryngitis, diarrhoea and weight loss before 1920 are presented to illustrate this similarity.

9. Possible reasons for differences in the frequency and severity of measles in different places and epochs are discussed. Differences in strains of the virus and host immunity seem unlikely factors, but liability to secondary infections may be of some importance. It is concluded that the severity of the disease is related to the manifestations of the rash. A dark rash, followed by profuse desquamation, is associated with equivalent changes in the larynx, bronchus, and intestines, which are likely to be responsible for the occurrence of bronchopneumonia, laryngitis and diarrhoea. Defective nutrition is a possible cause of the ‘vulnerability’ of the epithelium.

The analysis of the data from Nigeria was made possible by the payment of expenses to Dr Morley by the London School of Hygiene and Tropical Medicine from July 1960 to December 1961. Subsequently the work was supported by a grant from the Medical Research Council to Prof. B. S. Platt, Head of the Department of Human Nutrition, London School of Hygiene and Tropical Medicine.

The authors wish to thank Dr W. R. Aykroyd, Senior Lecturer, Department of Human Nutrition, for his encouragement and assistance in preparing the text, and Miss Allen and Miss Wise for secretarial help. They must also thank Professor Court of the Department of Child Health in the University of Durham for helpful criticism.

Aminoglycoside modifying enzymes (AMEs) are major factors which confer aminoglycoside resistance on bacteria. Distribution of genes encoding seven AMEs was investigated by multiplex PCR for 279 recent clinical isolates of enterococci derived from a university hospital in Japan. The aac(6′)-aph(2″), which is related to high level gentamicin resistance, was detected at higher frequency in Enterococcus faecalis (42·5 %) than in Enterococcus faecium (4·3 %). Almost half of E. faecalis and E. faecium isolates possessed ant(6)-Ia and aph(3′)-IIIa. The profile of AME gene(s) detected most frequently in individual strains of E. faecalis was aac(6′)-aph(2″)+ant(6)-Ia+aph(3′)-IIIa, and isolates with this profile showed high level resistance to both gentamicin and streptomycin. In contrast, AME gene profiles of aac(6′)-Ii+ant(6)-Ia+aph(3′)-IIIa, followed by aac(6′)-Ii alone, were predominant in E. faecium. Only one AME gene profile of ant(6)-Ia+aph(3′)-IIIa was found in Enterococcus avium. The ant(4′)-Ia and ant(9)-Ia, which have been known to be distributed mostly among Staphylococcus aureus strains, were detected in a few enterococcal strains. An AME gene aph(2″)-Ic was not detected in any isolates of the three enterococcal species. These findings indicated a variety of distribution profiles of AME genes among enterococci in our study site.

This study evaluated the epidemiology of Pseudomonas aeruginosa keratitis in contact lens (CL) wearers; the relationships between CL storage case contamination and CL hygiene practice and between CL hygiene and the development of keratitis. Sixteen CL wearers with keratitis were compared with 44 asymptomatic controls. Lens hygiene practice was assessed and CL care materials, domestic water sites and endogenous sites were evaluated microbiologically. Poor CL hygiene was not associated with Ps. aeruginosa keratitis. There was an association between keratitis and bacterial contamination of the CL and storage case (P < 0·0005). Lens and storage case contamination were not significantly associated with poor hygiene. No domestic or endogenous source for Ps. aeruginosa was found. Causative organisms may be derived from other sources, but CLs and CL storage cases provide a favourable environment for Ps. aeruginosa colonization. Changing the CL care environment to one less favourable for Ps. aeruginosa may help to eliminate this problem.

Non-typhoidal Salmonella is estimated to be the most common bacterial cause of foodborne illness in the United States, causing an estimated one million domestically acquired foodborne illnesses annually. Recent, large outbreaks have highlighted the importance of ground beef as an important source of multidrug-resistant Salmonella. We analysed the epidemiology of salmonellosis outbreaks that were attributed to beef in the United States reported to the Centers for Disease Control and Prevention (CDC) from 1973 to 2011. During 1973–2011, of the 1965 outbreaks of Salmonella where a food vehicle was implicated, 96 were attributed to beef, accounting for 3684 illnesses. We observed a shift in the type of beef implicated in salmonellosis outbreaks, from roast to ground beef. Delicatessen-style roast beef cooked in commercial processing establishments was the predominant type during the 1970s and early 1980s; regulations on cooking and processing essentially eliminated this problem by 1987. Ground beef emerged as an important vehicle in the 2000s; it was implicated in 17 (45%) of the 38 beef-attributed outbreaks reported during 2002–2011. Although this emergence was likely due in part to increased participation in CDC's PulseNet, which was established in 1996, and proactive decisions by the United States Department of Agriculture's Food Safety and Inspection Service, stronger measures are needed to decrease contamination of ground beef with Salmonella.

An outbreak of cryptosporidiosis resulted in 516 cases in Wiltshire and Oxfordshire. The outbreak caused widespread interest and led to an official inquiry. The majority of cases were in children; 8% of cases were admitted to hospital and the median duration of illness was 3 weeks. The geographical distribution of cases matched the distribution of water supplies from three treatment works and eryptosporidium oocysts were found at these works and in the treated water. Attack rates in electoral wards supplied by the three treatment works were significantly higher than in other wards. The cause of the outbreak appeared to be the failure of normal treatment to remove oocysts. Measures at the treatment works reduced the number of oocysts detected in treated water, after which the outbreak came to an end. The conclusion of the investigations was that cryptosporidiosis is a risk of conventionally treated public water supplies.

The prevalence of Neisseria meningitidis carriage is highest in teenagers and lowest in young children. In contrast, invasive meningococcal disease is most common in young children with a smaller secondary peak in teenagers. Data on carriage and disease were analysed to quantify the risks of infection and disease by age and serogroup. The forces of infection for serogroups B, C, other meningococci and Neisseria lactamica were modelled together with the risk of disease given infection for serogroups B and C, using maximum likelihood to fit the models to the available data. The risk of meningococcal disease given infection declines steeply through childhood and is higher for serogroup C than for serogroup B. The secondary peak in disease in teenagers appears to be explained mostly by increased transmission although there is a suggestion that other factors may also contribute. These analyses provide important insights and may be used to guide further data collection and modelling studies.

A study was conducted to isolate and identify microorganisms of medical importance from cockroaches (Blattella germanica) and to ascertain their vector potential in the epidemiology of nosocomial infections. Bacteria, fungi and parasites of medical importance were isolated and identified. Important bacterial pathogens responsible for wound infections, were further studies by antibiograms. One hundred and fifty-eight out of 159 (99·4%) cockroaches collected from hospital (test) and 113 out of 120 (94·2%) cockroaches collected from residential areas (control) were carrying medically important microorganisms (P < 0·05). A significantly higher (P < 0·001) number of test cockroaches were carrying a higher bacterial load (1 × 104 and 1 × 105) as compared to control cockroaches. Multiple drug-resistant bacteria were isolated from test cockroaches. The diversity of drug-resistant bacterial species isolated from test cockroaches suggests their involvement in the transmission of drug-resistant bacteria. Various fungi and parasitic cysts of medical importance were also isolated from the test and control cockroaches, but the carriage rates were low. The findings suggest that cockroaches, in hospitals, can act as potential vectors of medically important bacteria/parasites/fungi.

Epidemics of visceral leishmaniasis (VL) in major Brazilian cities are new phenomena since 1980. As determinants of transmission in urban settings probably operate at different geographic scales, and information is not available for each scale, a multilevel approach was used to examine the effect of canine infection and environmental and socio-economic factors on the spatial variability of incidence rates of VL in the city of Teresina. Details on an outbreak of greater than 1200 cases of VL in Teresina during 1993–1996 were available at two hierarchical levels: census tracts (socio-economic characteristics, incidence rates of human VL) and districts, which encompass census tracts (prevalence of canine infection). Remotely sensed data obtained by satellite generated environmental information at both levels. Data from census tracts and districts were analysed simultaneously by multilevel modelling. Poor socio-economic conditions and increased vegetation were associated with a high incidence of human VL. Increasing prevalence of canine infection also predicted a high incidence of human VL, as did high prevalence of canine infection before and during the epidemic. Poor socio-economic conditions had an amplifying effect on the association between canine infection and the incidence of human VL. Focusing interventions on areas with characteristics identified by multilevel analysis could be a cost-effective strategy for controlling VL. Because risk factors for infectious diseases operate simultaneously at several levels and ecological data usually are available at different geographical scales, multilevel modelling is a valuable tool for epidemiological investigation of disease transmission.

The distribution of 3001 cases of verocytotoxigenic Escherichia coli (VTEC) reported in the Province of Ontario, Canada, were examined to describe the magnitude of this condition geographically and to evaluate the spatial relationship between livestock density and human VTEC incidence using a Geographical Information System. Incidence of VTEC cases had a marked seasonal pattern with peaks in July. Areas with a relatively high incidence of VTEC cases were situated predominantly in areas of mixed agriculture. Spatial models indicated that cattle density had a positive and significant association with VTEC incidence of reported cases (P=0·000). An elevated risk of VTEC infection in a rural population could be associated with living in areas with high cattle density. Results of this study suggested that the importance of contact with cattle and the consumption of contaminated well water or locally produced food products may have been previously underestimated as risk factors for this condition.

We all recognise that some diseases are more “catching” than others. Every mother knows that measles is very catching and most people set aside a group of common complaints, measles, mumps, whooping-cough, scarlet fever, diphtheria—perhaps roughly in that order—as catching complaints. Then again, still keeping ourselves within the circle of ideas of educated non-medical people, one has such complaints as common colds or influenza which one thinks of as running through a house indeed but does not put quite into the measles category, as one feels that factors determine the spread other than mere proximity to a sick person. Lastly, one has some illnesses, gonorrhoea would be a fair example, which everybody recognises to be spread wholly by contagion, almost always by a particular method of contagion, but does not regard as catching at all in the sense that measles and whooping-cough are catching. When we enquire into the reasons of these opinions they will be found, I think, to be these.

Hoyle & Fairbrother (1937) showed that tissues infected with influenza virus contained two distinct particles, the infective virus elementary body, and a smaller particle, the soluble antigen, which could be demonstrated by complement-fixation tests.

An outbreak of food intoxication involving over 265 cases in western United States occurred in October 1991. Staphylococcus intermedius was implicated as the aetiologic agent. Representative outbreak isolates (five clinical and ten from foods) produced type A enterotoxin. DNA fragments generated by four restriction endonucleases and analysed by pulsed-field gel electrophoresis (PFGE) provided definitive evidence that all isolates from nine different counties in California and Nevada were derived from a single strain. The PFGE pattern of these outbreak isolates was distinct from those of a heterogeneous collection of seven S. intermedius strains of veterinary origin and five unrelated S. aureus laboratory strains. The data show a significant PFGE pattern heterogeneity not only among members of different Staphylococcus species but also within members of the same species and even the same enterotoxin type. The results indicate that PFGE is a valuable strain-specific discriminator for the epidemiological characterization of S. intermedius. To our knowledge, this represents the first documented foodborne outbreak caused by S. intermedius. These findings suggest that the presence of S. intermedius and other species such as S. hyicus in food should be reason for concern.

Between 1976 and 1986, 258 incidents of suspected scombrotoxic fish poisoning were reported in Britain. Histamine analysis was carried out on 240 fish samples from these incidents, and 101 were found to contain > 5 mg histamine/100 g fish. The symptoms most consistently reported were rash, diarrhoea, flushing and headache. In recent years there has been a decrease in the number of confirmed scombrotoxic outbreaks and a trend towards more sporadic incidents. Of fish samples with > 20 mg histamine/100 g, 94% were from incidents in which scombrotoxic symptoms were characteristic, but where fish had 5–20 mg/100g only 38% of incidents were clinically distinctive. Guidelines are presented based on the interpretation of quantitative histamine analysis of fish samples from scombrotoxic poisoning incidents.

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.

The survival and growth of toxigenic Vibrio cholerae 01 in water under various conditions of salinity, pH, temperature and cation composition and concentration were studied in an extensive series of laboratory experiments. Inter- and intra-strain variation in stress response (of 01 and non-01 strains) and the ability of V. cholerae to adapt to stressful environments were also studied. Toxigenic V. cholerae 01 were able to survive for at least 70 days at 25 °C in solutions of sea salt. The optimal salt concentration was 2·0% though all solutions in the range 0·25–3·0% gave good support. Substrains with enhanced capacity to persist at sub-optimal salinity (0·1%) were demonstrated. A great degree of inter-strain variation in stress response at low salinity (0·05%) was found among 59 strains, and this variation was unrelated to serogroup (01 or non-01), source (clinical or environmental) or country of origin (Tanzania or Bangladesh). At optimal salinity, inter-strain variation was less and 18 out of 20 strains remained viable at high concentrations for at least 40 months at 25 °C. V. cholerae 01 could not survive beyond 45 days at 4 °C and optimal salinity, either with or without nutrients. The optimal pH range for survival at 25 °C was 7·0–8·5 at optimal salinity, and 7·5–9·0 at low salinity. V. cholerae 01 require Na+ for survival in the absence of nutrients, and for enhanced growth in their presence. The presence of Ca2+ or Mg2+, in addition to Na+, further enhanced survival. These, and other results reported in this paper, suggest that toxigenic V. cholerae 01 are able to survive for extended periods in warm water containing no nutrients but having a salinity of 0·25–3·0% and a pH of around 8·0. With added nutrients and under the same conditions, rapid growth is possible. The implications of these findings for the identification of putative aquatic reservoirs of V. cholerae 01, and for the epidemiology of cholera, are considerable.

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.

National studies determining the burden of gastroenteritis have defined gastroenteritis by its clinical picture, using symptoms to classify cases and non-cases. The use of different case definitions has complicated inter-country comparisons. We selected four case definitions from the literature, applied these to population data from Australia, Canada, Ireland, Malta and the United States, and evaluated how the epidemiology of illness varied. Based on the results, we developed a standard case definition. The choice of case definition impacted on the observed incidence of gastroenteritis, with a 1·5–2·1 times difference between definitions in a given country. The proportion of cases with bloody diarrhoea, fever, and the proportion who sought medical care and submitted a stool sample also varied. The mean age of cases varied by <5 years under the four definitions. To ensure comparability of results between studies, we recommend a standard symptom-based case definition, and minimum set of results to be reported.

Human rotaviruses from the states of Rio de Janeiro, São Paulo and Pará of Brazil were analysed by RNA electrophoresis. At least some bands characteristic of rotavirus double-stranded RNA were detected in 138 (86·8%) of 159 faecal samples in which the presence of rotavirus had been demonstrated by enzyme immunoassay. Of the RNA-positi ve samples, 18 (13·0%) were classified as subgroup 1, 94 (68·1%) as subgroup 2, and 26 (18·8%) could not be classified due to absence of visible bands 10 and 11. Subgroup 2 was more frequent in the three states. All strains of subgroup 1 detected in Rio de Janeiro were associated with a single short-lived school outbreak. All strains of subgroup 1 resembled each other in electrophoretie pattern, irrespective of geographical origin, although minor differences could be detected by co-electrophoresis. Subgroup 2, on the other hand, showed a great degree of electrophoretic heterogeneity and could be divided into several sub-categories.