Helicobacter pylori infection plays a role in the development of chronic gastritis, peptic ulcer and gastric cancer, yet the route of transmission into susceptible hosts remains unknown. Studies employing microbiological techniques have demonstrated that H. pylori has the ability to survive when introduced into water and that H. pylori is present in water and other environmental samples all over the world. Epidemiological studies have shown that water source and exposures related to water supply, including factors related to sewage disposal and exposure to animals, are risk factors for infection. This review describes the microbiological and epidemiological evidence for, and proposes a model of, waterborne H. pylori transmission outlining important features in the transmission cycle. In the model, humans and animals shed the bacteria in their faeces and the mechanisms for entry into water, and for survival, ingestion and infection are dependent upon a range of environmental influences. Verification of the proposed model pathways has important implications for public-health prevention strategies.

Helicobacter pylori is transmitted within households and high concordance is observed among siblings. To better understand the contributions of close interpersonal contact and family relatedness to transmission, we compared concordance of H. pylori infection among 241 sibling and non-sibling children aged 2–18 years in 68, predominantly low-income, Hispanic households with at least two nuclear families. Prevalence of H. pylori infection was 24%. Compared to children with no infected siblings or non-siblings and adjusting for age, odds of H. pylori infection were 1·2 (95% CI 0·52–2·9), 3·2 (95% CI 1·14–9·1), and 9·4 (95% CI 3·1–28·5) for children residing with at least one infected non-sibling, one infected sibling, and with at least one infected sibling and non-sibling, respectively. The study further implicates intersibling transmission as a pathway for H. pylori infection in childhood. In addition, living with a non-sibling in extended-family homes may contribute to infection risk but only in households with prevalent H. pylori infection within all family groups.

Helicobacter pylori prevalence is elevated in German submarine crews and in United States Navy (USN) surface fleet personnel, but H. pylori prevalence in USN submariners was unknown. The goal of the study was to determine the prevalence of H. pylori in the crews of USN nuclear submarines compared to other military personnel and to the general US population. The presence of H. pylori IgG antibodies was determined in serum samples using a commercial ELISA. Only 47 out of 451 submariners (9·4%) were H. pylori positive, which is similar to that of the US general population with a similar level of education. In contrast, H. pylori prevalence is significantly higher in US Army recruits (26%), USN surface fleet personnel (25%), and German diesel submariners (38%). These data demonstrate that submarine service (and by inference activity requiring isolation and close contact, per se) is not a risk factor for H. pylori infection.

To examine work-related blood and body fluid exposure (BBFE) among health-care workers (HCWs), to explore potential risk factors and to provide policy suggestions, a 6-year retrospective study of all reported BBFE among HCWs (1998–2003) was conducted in a 430-bed teaching hospital in Australia. Results showed that BBFE reporting was consistent throughout the study period, with medical staff experiencing the highest rate of sharps injury (10·4%). Hollow-bore needles were implicated in 51·7% of all percutaneous injuries. Most incidents occurred during sharps use (40·4%) or after use but before disposal (27·1%). Nursing staff experienced 68·5% of reported mucocutaneous exposure. Many such exposures occurred in the absence of any protective attire (61·1%). This study indicated that emphasis on work practice, attire, disposal systems and education strategies, as well as the use of safety sharps should be employed to reduce work-related injuries among HCWs in Australia.

The aim of this study was to describe the natural history of HCV after 16 years of infection, in a cohort of individuals who acquired their infections on a known date in the United Kingdom. A total of 924 HCV-infected transfusion recipients (cases) and 475 anti-HCV negative transfusion recipients (controls) were eligible for inclusion in the study. Survival was compared between cases and controls to see if there was any excess mortality attributable to HCV. The results show that all-cause mortality was not significantly different between cases and controls (hazard ratio 1·17, 95% CI 0·92–1·49, P=0·21). However, the risk of death directly from liver disease was higher in cases than controls (hazard ratio 2·71, 95% CI 1·09–6·75, P=0·03). Nearly 30% of those HCV-infected cases who died directly from liver disease were known to have consumed excess alcohol.

Hepatitis C virus (HCV) and hepatitis B virus (HBV) are highly prevalent, often co-occuring infections among drug users. We examined HBV prevalence and risk behaviour patterns among a group of HCV-negative heroin and/or cocaine users in order to understand HBV risk and prevention opportunities among this unique group. Of 164 people enrolled, 44% had injected drugs. Overall, 24% of participants tested positive for exposure to HBV; drug injectors (28%) were only slightly and not significantly (P=0·287) more likely to test positive than those who had never injected drugs (21%). HBV exposure was significantly associated with multiple indicators of greater sex risk. HBV status was not associated with any demographic characteristic, but participants who reported longer duration of cocaine use were significantly less likely to test positive to exposure for HBV. It appears that HBV risk among HCV-negative drug users in this cohort is primarily due to sexual behaviour.

From August 2002 to February 2003 25 cases of hepatitis A were notified from one town in Jutland. The first cases were children of three families who returned from an endemic country. The infection spread subsequently in the local community and within households. A case-control study among household index cases showed that hepatitis A was associated with contact to a case in an after-school group (OR 29·6) and with contact to a case household member in a school class or day-care centre group (OR 9·5). From a serosurvey it was estimated that for each notified patient approximately one additional infection has occurred in the households. The infection was imported by children of immigrants, born in Denmark, returning from a visit to friends and relatives in the high-incidence country of origin of their parents and was then propagated through contact between children in after-school groups, schools and their families. Immunoprophylaxis should be given to children prior to visits to friends and relatives in endemic countries and to case contacts.

In the rapidly developing city of Almaty, Kazakhstan, rates of hepatitis A have fallen, but no data on prevalence of antibody to hepatitis A virus (anti-HAV) exist with which to interpret incidence data. In the autumn of 2001, we determined the anti-HAV prevalence among household and school contacts of hepatitis A cases. For contacts aged 0–4 years, 5–9 years, 10–14 years, 15–19 years, or 20–30 years, immune prevalences were 9, 12, 33, 33 and 77% respectively, among immediate-family household contacts and 15, 28, 49, 52 and 77% respectively, among community contacts. Child community contacts were more likely to be immune than their immediate-family household counterparts (odds ratio 2·0, 95% confidence interval 1·3–3·2). Almaty is experiencing an epidemiological shift in hepatitis A incidence. Feasible and effective prevention strategies using hepatitis A vaccine should be explored.

At the University Hospital of Besançon (département of Doubs, France), an unusually high number of patients were hospitalized for hepatitis A during the 1999–2000 period, some of whom had not travelled abroad. This prompted us to conduct an investigation on a population basis and search for clusters of cases possibly related to local sources of contamination. Accordingly, case definition was restricted to autochthonous cases. During the 1999–2002 period, 45 autochthonous cases were classified as possibly originating from local environmental sources. A space–time scan statistic detected one most likely cluster (standardized incidence ratio 20·63, 95% confidence interval 10·6–37·1), consisting of 11 persons (of whom five children had attended the same swimming pool). It remained significant in a sensitivity analysis, strongly supporting the hypothesis of an environmental source of contamination. This study reveals the necessity of regular surveillance for hepatitis A and raises the issue of virological surveys of pool waters.

This study analysed the role of several risk factors for hospitalization due to community-acquired, respiratory syncytial virus (RSV) infection. The risk factors detected in infants hospitalized for RSV infection in the first 24 months of life were compared with those in the general infant population in our region. There were 361 episodes of hospitalization in 357 infants. Eighty per cent of the infants did not present underlying conditions for severe RSV infection and only 10 (3%) were candidates for palivizumab prophylaxis. In multivariate analysis, birthweight of <2500 g was independently associated with hospitalization for RSV infection and was the most commonly detected medical risk factor. Other risk factors were maternal age at delivery <25 years, birth in the second half of the year, prematurity, suburban residence and congenital heart disease. In conclusion, together with well-known risk factors, we found that low birthweight was an independent factor for severe RSV infection.

The genetic variability of influenza virus is usually studied with sequences selected over numerous years and countries, and rarely within a single season. Here we examined the viral evolution and the correlation between genetic and clinical features during an epidemic. From a French prospective household-based study in 1999–2000, 99 infected patients were randomly selected. The HA1 genomic domain was sequenced. Phylogenetic analysis showed the existence of two groups of A/H3N2 viruses. We found no distinct pattern of genomic evolution within either group according to time. A spatial correlation with the nucleotide distances was shown. The average nucleotide diversity was 3·4×10−3 nucleotides per site, and did not differ between the groups. A lower number of segregating sites was observed in patients who experienced influenza-like symptoms during the previous epidemic. These results suggest that the influenza virus undergoes regular HA1 nucleotide changes, but without clonal expansion of mutant strains within a single epidemic.

Red squirrels are declining in the United Kingdom. Competition from, and squirrel poxvirus (SQPV) disease carried by, grey squirrels are assumed to be determining the decline. We analyse the incidence of disease and changes in distribution of the two species in Cumbria, from 1993 to 2003 and compare these to the predictions of an individual-based (IB) spatially explicit disease model simulating the dynamics of both squirrel species and SQPV in the landscape. Grey squirrels increased whilst red squirrels declined over 10 years. The incidence of disease in red squirrels was related to the time since grey squirrels arrived in the landscape. Analysis of rates of decline in red squirrel populations in other areas showed that declines are 17–25 times higher in regions where SQPV is present in grey squirrel populations than in those where it is not. The IB model predicted spatial overlap of 3–4 years between the species that was also observed in the field. The model predictions matched the observed data best when contact rates and rates of infection between the two species were low. The model predicted that a grey squirrel population control of >60% effective kill was needed to stop the decline in red squirrel populations in Cumbria.

Three physically separate incursions of the raccoon strain of rabies have entered Canada, two into eastern Ontario in 1999 and one into New Brunswick in 2000. The course of these epizootics is described. Phylogenetic analysis of the index cases from these two provinces with raccoon rabies viruses representative of this strain in the United States supported the independence of these incursions into Canada via cross-border transmission from the United States. Genetic characterization of 190 isolates from these two Canadian provinces over a 550-bp region of the variable central portion of the viral P gene distinguished 14 variants in Ontario and five in New Brunswick although in both regions the variant represented by the initial case was most commonly encountered. The quasi-species nature of the Ontario virus was analysed using isolates taken at different times during the main outbreak to examine whether viral variation was increasing with time as well as changing in nature. These data provide a framework for study of future incursions of this rabies strain into Canada.

The purpose of our retrospective 3-year study was to analyse and compare clinical and epidemiological characteristics in hospitalized patients older than 6 years with community-acquired pneumonia (CAP) caused by Chlamydia pneumoniae (87 patients) and Mycoplasma pneumoniae (147 patients). C. pneumoniae and M. pneumoniae infection was confirmed by serology. C. pneumoniae patients were older (42·12 vs. 24·64 years), and were less likely to have a cough, rhinitis, and hoarseness (P<0·001). C. pneumoniae patients had higher levels of C-reactive protein (CRP), and aspartate aminotransferase (AST) than M. pneumoniae patients (P<0·001). Pleural effusion was recorded more frequently in patients with M. pneumoniae (8·84 vs. 3·37%). There were no characteristic epidemiological and clinical findings that would distinguish CAP caused by M. pneumoniae from C. pneumoniae. However, some factors are indicative for C. pneumoniae such as older age, lack of cough, rhinitis, hoarseness, and higher value of CRP, and AST.

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.

We examined the epidemiology of community-acquired bacterial meningitis among adults in England and Wales between 1991 and 2002. Among 3169 cases, meningococcal infection was predominant among young adults and pneumococcal meningitis among older adults. Whilst infection due to most causes decreased, the incidence of tuberculous (TB) meningitis doubled over the 12 years. The mortality rate among meningococcal and pneumococcal infections fell from 0·45/105 to 0·31/105 (P=0·0001). This study demonstrates important changes in the epidemiology of bacterial meningitis among UK adults. Improvements in clinical management, childhood vaccination programmes and the re-emergence of tuberculosis are likely to be drivers of these changes.

Paediatric cases of epiglottitis declined markedly in England following the introduction of safe effective immunization against Haemophilus influenzae type b (Hib). With the recently described resurgence in Hib infections, a corresponding rise in the number of presentations of clinical epiglottitis in children was observed, although numbers were still well below those reported prior to vaccine availability. This was seen both in microbiology reports and hospital admissions data for England. In keeping with the more diverse aetiology of epiglottitis in adults, Hib vaccination had minimal impact on hospital presentations with upper airway infections in those aged 15 years and over, which showed an overall increasing trend over 10 years. The need for a high index of suspicion to allow early diagnosis of this life-threatening clinical presentation is reinforced.

A large serosurvey was carried out in Luxembourg in 2000–2001, to determine the population immunity against a number of vaccine-preventable infections including diphtheria and pertussis. Immunity to diphtheria and pertussis was assessed using an in-house neutralization assay and a commercial ELISA test respectively. Mean pertussis antibody activity decreased from 4 to 8 years of age, reflecting the effects of waning of vaccine-induced immunity. Mean pertussis antibody activity increased during adolescence due to infection in previously vaccinated individuals and levelled out after approximately 20 years of age. For adults >25 years age, a statistically significant 30% difference in mean antibody activity between men and women was observed. The proportion of seronegatives for diphtheria among children and adolescents aged <20 years was 2·5% reflecting the high vaccination coverage. The proportion seronegative for diphtheria tended to increase with age such that 42% of individuals aged >40 years were seronegative. Our study supports the recently introduced acellular pertussis vaccine booster at 6 years to reduce pertussis transmission in school-aged children and adolescents.

The distribution of antibody levels to Legionella (L.) pneumophila (serotypes 1–7) was compared between subjects who worked near the source of a large outbreak of Legionnaires' disease (n=668) and a population sample of comparable age (n=480). In a previous analysis of these data, it was estimated that 80% of those working near the source were infected with L. pneumophila. However, the estimation procedure implicitly assumes that the probability of infection does not depend on the antibody level of a person before exposure. This is questionable, as antibodies could protect against infection. We have now estimated the minimum value consistent with the data on the number of infected persons. We observed that a minimum of 40% [95% confidence interval (CI) 32–48] of those working near the source and 13% (95% CI 8–18) of those working further away were infected with L. pneumophila. Implications of these findings for design options in future research are discussed.

This paper describes the features of an outbreak of early syphilis in an institution for the care of adults with mental disorders. A case-note review was performed. In the period June to November 2001, 87 cases of syphilis were diagnosed [25 primary, 21 secondary and 41 early latent syphilis in 983 inmates (crude attack rate 8·9%)]. Among them 82 were heterosexual, four were homosexual or bisexual, and for one case sexual preference was not established. About half the cases were known to be promiscuous. The initial case was not identified. Penicillin therapy was administered to all cases and all known or suspected sexual contacts. Sporadic cases of syphilis have, however, continued to emerge from time to time. Institutions for patients with mental disorders are vulnerable to sexually transmitted diseases, and special strategies should be devised for their control.