It has come to our notice that a paper we published in Epidemiology & Infection contained a substantial amount of previously published material.

Hepatitis A virus (HAV) is spread by faecal–oral contact or ingestion of contaminated food or water. Lifelong immunity is conferred by infection or vaccination, so anti-HAV seroprevalence studies can be used to indicate which populations are susceptible to infection. Seroprevalence rates are highly correlated with socioeconomic status and access to clean water and sanitation. Increasing household income, education, water quality and quantity, sanitation, and hygiene leads to decreases in HAV prevalence. Japan, Australia, New Zealand, Canada, the United States, and most European nations have low anti-HAV rates. Although anti-HAV rates remain high in most Latin American, Asian, and Middle Eastern nations, average seroprevalence rates are declining. Surveys from Africa generally indicate no significant decline in anti-HAV rates. Because the severity of illness increases with age, populations with a high proportion of susceptible adults should consider targeted vaccination programmes.

We explored the dual influence of the patient's age and the infecting serotype on the blood invasiveness patterns of non-Typhi Salmonella enterica (NTS). Blood invasiveness ratio (BIR) was calculated as the ratio between the number of blood and blood+stool isolates. Analysis of 14951 NTS isolates showed that the BIR increased drastically above the age of 60 years, reaching levels 3·5–7 times higher compared to age group <2 years. Different patterns of age-related invasiveness were observed for the five most common NTS serotypes (Enteritidis, Typhimurium, Virchow, Hadar, Infantis). Among children <2 years, the BIR was highest for serotype Virchow and lowest for serotype Hadar, while in persons [ges ]60 years it was highest for serotypes Enteritidis and lowest for serotype Infantis. The tendency of NTS serotypes to invade the bloodstream was significantly influenced by the patient's age, however the impact of age differed for various NTS serotypes.

Previous studies showed differences in in vitro heterophil function between parental (A>B) broilers and F1 reciprocal crosses (D>C). Our objectives were to (1) determine if in vitro variations translate to differences in resistance to Salmonella enteritidis (SE) and (2) quantitate cytokine mRNA in heterophils from SE-infected chicks. One-day-old chicks were challenged and organs were cultured for SE. Chicks with efficient heterophils (A and D) were less susceptible to SE compared to chicks with inefficient heterophils (B and C). Heterophils were isolated from SE-infected chicks and cytokine mRNA expression was evaluated using quantitative real-time RT–PCR. Pro-inflammatory cytokine mRNA was up-regulated in heterophils from SE-resistant chicks compared to susceptible chicks. This is the first report to quantitate cytokine mRNA in heterophils from SE-infected chicks. These data show a relationship between in vitro heterophil function, increased pro-inflammatory cytokine mRNA expression, and increased resistance to SE in 1-day-old chicks.

F4+ Escherichia coli is an important agent of post-weaning diarrhoea in piglets. Piglets that express an adhesion site for F4+ E. coli in their small intestine (F4R+) shed higher numbers of F4+ E. coli than piglets lacking this site (F4R−). We hypothesized that F4R+ piglets are more infectious and more susceptible for F4+ E. coli. This implies that in populations with F4R+ and F4R− piglets, the transmission would be dependent on the frequency of both types of animals. To quantify the difference in infectiousness and susceptibility, a one-to-one transmission experiment was performed with 20 pairs consisting of one inoculated and one contact piglet. Based on the contact infections observed, transmission parameters were estimated with generalized linear models. F4R+ piglets were infectious for other piglets and the reproduction ratio (R0) for homogeneous F4R+ populations, that is the average number of secondary infections that one F4R+ pig will cause during its entire infectious period in a population of susceptible F4R+ individuals only, was estimated as 7·1. F4R+ piglets were more susceptible than F4R− piglets and reducing the fraction of F4R+ piglets of a population will reduce transmission. It was calculated that in order to prevent major outbreaks of F4+ E. coli (R0<1), the fraction of F4R+ piglets must be lower than 0·14.

This is a surveillance study of the antimicrobial resistance of the S. flexneri group in the context of its serotype diversity. It includes 1422 isolates, which were sent to the National Shigella Reference Centre (NSRC) by hospitals and outpatient clinics in Israel during a 3-year period (2000–2002). The strains were identified and classified according to the prevalence and antigenic structure of their serotypes. All samples were checked for resistance to ampicillin (AMP), trimethoprim–sulphamethoxazole (TMP–SMX), ceftriaxone (CRO), tetracycline (TE), nalidixic acid (NAL), and chloramphenicol (C) by the disk diffusion method of Bauer et al. There were significant differences in their resistance to the individual antimicrobials with resistance to AMP, TE and C being lower among the strains of serotype 6 than among those of serotypes 2a and 1b. The resistant phenotypes were also serotype-specific. The similarities both in individual and in phenotype resistance between the rare and the prevalent serotypes (but not serotype 6) may be attributed to their antigenic relatedness. The serospecificity of the antimicrobial resistance was not affected by external factors such as seasonality and source (hospital or outpatient laboratory) of the isolates, and the age and sex of the patients. The serotype-specific approach can assist in properly assessing the problem of the antimicrobial resistance of the Shigella flexneri group and may prove useful for the empirical therapy of shigellosis. The observed interdependency between resistance and the antigenic specificity and relatedness of the S. flexneri serotypes requires additional investigation.

The presumptive treatment of parasitosis among immigrants with albendazole has been shown to save both money and lives, primarily via a reduction in the burden of Strongyloides stercoralis. Ivermectin is more effective than albendazole, but is also more expensive. This coupled with confusion surrounding the cost-effectiveness of guiding therapy based on eosinophil counts has led to disparate practices. We used the newly arrived year 2000 immigrant population as a hypothetical cohort in a decision analysis model to examine the cost-effectiveness of various interventions to reduce parasitosis among immigrants. When the prevalence of S. stercoralis is greater than 2%, the incremental cost-effectiveness ratios of all presumptive treatment strategies were similar. Ivermectin is associated with an incremental cost-effectiveness ratio of $1700 per QALY gained for treatment with 12 mg ivermectin relative to 5 days of albendazole when the prevalence is 10%. Any presumptive treatment strategy is cost-effective when compared with most common medical interventions.

The spatial epidemiology of intestinal nematodes in Uganda was investigated using generalized additive models and geostatistical methods. The prevalence of Ascaris lumbricoides and Trichuris trichiura was unevenly distributed in the country with prevalence greatest in southwest Uganda whereas hookworm was more homogeneously distributed. A. lumbricoides and T. Trichiura prevalence were nonlinearly related to satellite sensor-based estimates of land surface temperature; hookworm was nonlinearly associated with rainfall. Semivariogram analysis indicated that T. trichiura prevalence exhibited no spatial structure and that A. lumbricoides exhibited some spatial dependency at small spatial distances, once large-scale, mainly environmental, trends had been removed. In contrast, there was much more spatial structure in hookworm prevalence although the underlying factors are at present unclear. The implications of the results are discussed in relation to parasite spatial epidemiology and the prediction of infection distributions.

Streptococcus pneumoniae (pneumococcus) is one of the most important bacterial pathogens and a leading cause of mucosal infections (e.g. otitis media) and various forms of serious diseases (e.g. pneumonia, meningitis, bacteraemia) in developing and developed countries. Based on the polysaccharide capsule, there are at least 90 different pneumococcal serotypes, which may compete with each other to colonize the nasopharynx. Newly developed protein–polysaccharide conjugated vaccines have been shown to provide protection against disease caused by the serotypes included in the vaccine, and also against colonization (carriage). It is feared that yet uncommon, but nonetheless pathogenic serotypes which have been suppressed by competition, may become more prevalent in carriage and disease after large-scale use of conjugate vaccines. In this paper, we use transmission models of pneumococcal carriage to study how competition and vaccination influence the coexistence of two serotypes. According to our results, direct (physical) competition between two pneumococcal serotypes only influences colonization if the duration of naturally acquired immunity is short. By contrast, indirect (antibody-mediated) competition is of influence only if naturally acquired immunity is long lasting. Vaccination reduces the prevalence of the target serotype – an effect that is enforced by the presence of directly competing bacteria. The emergence of a non-target serotype after vaccination is only observed if bacteria compete directly. These results emphasize the importance of studying whether bacteria compete directly or indirectly and for how long people are protected in order to assess the long-term effects of sero-competition.

During the period 1984–2002, 472 cases of invasive group B streptococcal (GBS) disease in infants aged 0–90 days in Denmark were registered. The overall incidence was 0·4/1000 live births. Most infants (73%) had early-onset GBS infection with 53% registered within the first day. Serotype III predominated (59%) with other serotypes as follows: Ia (16%), Ib (8%), NT (7%), II (6%), other serotypes (5%). Recurrence of GBS infection was registered in six infants, and the interval with no antibiotic therapy varied from 2 to 39 days. The serotypes of the isolates obtained from first and second episodes were identical (serotype III in five, and serotype Ia in one infant). Paired isolates were indistinguishable by PFGE and antibiotic susceptibility testing. Invasive GBS infections in infants are still a problem in Denmark, and recurrent infections are registered in 1% of these infants.

Although reports of isolation of methicillin-resistant Staphylococcus aureus (MRSA) from patients admitted from the community have increased, few studies have investigated colonization of healthy subjects. This study aimed to determine community levels of MRSA in Hong Kong. Nasal swabs from a cross section of young adults and family units were cultured for MRSA. Antibiotic sensitivities and risk factors for carriage were determined and clonal relationships were investigated by pulsed-field gel electrophoresis (PFGE). Overall carriage was low (1·4%), and associated with health-care exposures (OR 13·56, 95% CI 1·11–165·21). Subjects working in health care yielded multi-resistant MRSA strains, but isolates from non-hospital-exposed subjects were methicillin-resistant only. Strains indistinguishable by PFGE were carried by subjects working together, and some spread to other contacts was observed. MRSA colonization in the community is rare in Hong Kong and is largely associated with working in health care. Community-acquired staphylococcal infections may be treated with agents effective against methicillin-sensitive strains.

Drug-resistant tuberculosis can be transmitted (primary) or develop during the course of treatment (secondary). We investigated risk factors for each type of resistance. We compared all patients in England and Wales with isoniazid- and multidrug-resistant tuberculosis in two time-periods (1993–1994 and 1998–2000) with patients with fully sensitive tuberculosis, examining separately patients without and with previous tuberculosis (a proxy for primary and secondary drug-resistant tuberculosis). Patients with previous tuberculosis smear positivity and arrival in the United Kingdom <5 years were strongly associated with multidrug resistance and isoniazid resistance. In patients with no previous tuberculosis HIV infection, residence in London and foreign birth were risk factors for multidrug resistance, and non-white ethnicity, residence in London and HIV infection for isoniazid resistance. Risk factors for each type of resistance differ. Elevated risks associated with London residence, HIV positivity, and ethnicity were mainly seen in those without previous tuberculosis (presumed transmission).

The epidemiological features and clinical manifestations of adult cases of brucellosis admitted to the Department of Infectious Diseases, Babol Medical University, Iran from 1997 to 2002 were investigated. Of 469 cases, 267 (56·9%) were males. The mean age of cases was 36·9±15 years. Most (60·8%) were from rural areas. Two thirds of cases (306, 66·3%) presented during spring or summer. Fresh cheese (22·4%), animal husbandry (11·3%), laboratory worker (8·1%) and veterinary profession (1·5%) were the main risk factors. Forty-five families (9·6%) had two cases. Sweating, fever, and arthralgia were the most frequent clinical symptoms. Complications were documented in 105 males (39·5%) and 41 females (20·3%, P=0·0001). Peripheral arthritis was seen in 24 (9%) males and 19 (9·4%) females, with knees and hips being the most common sites of infection. Sacroiliitis and spondylitis were seen in 28 (6%) and 32 (6·8%) cases respectively with spondylitis more common in males (P=0·023). Epididymo-orchitis was seen in 29 (10·9%) males. There were three cases each of endocarditis (0·6%) and neurological complications (0·6%). Most patients with brucellosis did not have any of the known risk factors for brucellosis. Thus consumption of unsafe dairy products could be the main route of infection. The disease manifested with a diversity of clinical manifestations and complications. Complications were more frequent in males than females.

Leptospirosis is an important public health problem in the Andaman Islands. The disease is being increasingly reported among children and adolescents in recent times. An attempt was made to find out the level of exposure to leptospires, to estimate the incidence of infection and to identity the risk factors for acquiring infection among children. A sample of 1544 schoolchildren was selected. Presence of anti-leptospiral antibodies was tested using the microscopic agglutination test (MAT). Students were interviewed for behavioural factors. In total, 341 (221 seronegative and 120 seropositive) students were followed up clinically and serologically during a subsequent outbreak. An overall seropositivity rate of 23·6% (95% CI 21·54–25·81) was observed. Infection rate was 33·5% among seronegatives whereas re-infection rate was 16·7% among seropositives during the outbreak that occurred 1 month after the first sample collection. Morbidity and mortality were found to be higher among seronegative individuals than serpositives, More than 90% of leptospiral infections were found to be subclinical or unnoticed. The high level of exposure among the children results in high infection rates and because they have less previous exposure than adults, they do not have sufficient protection to resist clinical illness during outbreaks.

A serological prevalence survey was carried out in Luxembourg during 2000–2001 to determine the antibody status of the Luxembourg population against vaccine-preventable infections including varicella-zoster virus (VZV). ELISA tests performed on 2679 sera indicated that 96 (3·6%) of the study population were seronegative. Age-specific seroprevalence rose rapidly from approximately 70% at age 4 years to 90% at age 6 years to 95% at age 12 years. Significant heterogeneity of seroprevalence was observed between the six different primary schools. For age groups 0–5, 6–11 and 12+ years, we estimated an annual force of infection of 0·361 [95% confidence interval (CI) 0·31–0·415)], 0·204 (95% CI 0·12–0·29) and 0·05 (95% CI 0·024–0·082) respectively. Our results indicate that transmission of VZV is highest in children below the age of 6 years and that much lower levels of VZV transmission occur in secondary schools and throughout adulthood.

This is the first large-scale study to investigate the seroprevalence of varicella zoster (VZV) in the general population of England and Wales. The study focused on those aged 1–20 years, that age group in whom most infections occur. Prevalence rose rapidly with age, with 53% of children showing evidence of prior infection by the age of 5 years and most young adults having experienced infection. In addition to using a fixed cut-off recommended by the manufacturer, a mixture modelling technique was also used to define the proportion of the population seropositive in each age group. This was shown to be a more accurate approach to categorizing data from an epidemiological perspective.

Inclusion of live varicella vaccine in the routine occupational health vaccination schedule requires knowledge of the natural immunity to varicella zoster virus (VZV) among high-risk occupations. This study aims were to evaluate VZV antibody positivity among health-care workers (HCWs) and day-care-centre workers (DCWs) and to assess its association with potential risk factors. Three groups of workers were tested for VZV antibody positivity: hospitals and community clinic HCWs (n=335), DCWs (n=117) and blue-collar workers as controls (n=121). The total VZV antibody positivity was 94·4%. There was no significant difference in VZV antibody positivity among study groups. DCWs had the lowest VZV seroprevalence (90·9%, 95% CI 85·7–96·1) and controls the highest (96·6%, 95% CI 93·2–99·9). This high VZV antibody positivity suggests that no special occupational measures are indicated in health-care or day-care occupational settings in Israel. On-going monitoring of the natural immunity to VZV is necessary to detect trends over time.

Prevalence and incidence measures are the common way to describe epidemics. The reproduction number supplies information on the potential for growth or decline of an epidemic. We define an actual reproduction number for infectious disease transmission that has taken place. An estimator is suggested, based on the number of new infections observed in a given time-interval, the number of those infected at the start of the interval, and the length of the infectious period. That estimator is applied to HIV among men having sex with other men over the period, 1977–1995, in Scandinavia. The actual reproduction number was estimated with acceptable certainty from the period, 1981–1982, yielding a value of 15 secondary cases. A value of less than one secondary case was assessed for the period, 1988–1995, in Denmark and Sweden. The actual reproduction number gives us some additional understanding of the dynamics of epidemics, compared with prevalence and incidence curves.

The majority of those infected and affected by HIV are younger adults. The ability of highly active antiretroviral therapies (HAART) to extend survival means that those infected when younger may reach older age, and future increases in numbers of older individuals living with HIV in England, Wales and Northern Ireland (E,W&NI) are expected. Evidence that older individuals engage in risky sexual behaviours suggests potential for HIV transmission. Data from national HIV/AIDS surveillance systems were reviewed (1997–2001). An older individual is defined as aged 45 years or over. Between 1997 and 2001, 2290 older individuals were diagnosed with HIV; 361 in 1997, rising to 648 in 2001. Heterosexual acquisition accounted for 1073 (47%) infections; 662 were male. Where reported, 666 (65%) older heterosexuals were probably infected in Africa, 144 (14%) in the United Kingdom and 113 (11%) in Asia. There were 1020 (45%) new diagnoses acquired homosexually; white (92%), infected in the United Kingdom (78%). Numbers of older individuals accessing HIV-related services more than doubled between 1997 (2488) and 2001 (5175). In 2001, 2270 (53%) were London residents. Between 1997 and 2001, among HIV-infected older individuals attending genitourinary medicine (GUM) clinics, the proportions previously undiagnosed were 60% and 82% in heterosexual males and females respectively, and for men who have sex with men (MSM), 42%. Numbers of older individuals newly diagnosed with HIV have increased in recent years. The increase in numbers of older individuals accessing HIV-related services were in excess of younger adults. A significant proportion of older HIV-infected female heterosexuals and MSM were undiagnosed. Awareness must be raised among clinicians, and an ‘aged response’ to HIV is required.

Blood, donated by asymptomatic donors, may contain and transmit parvovirus B19. To investigate the dynamics of parvovirus viraemia in asymptomatic blood donors, we studied the amounts of parvovirus DNA in pools of donor plasma, the prevalence of parvovirus antibodies among blood donors in relation to age, and the seasonal and year-to-year variation of the incidence of parvovirus infection in The Netherlands. The incidence of parvovirus infection follows a seasonal cycle and a cycle of several years. Among Dutch blood donors the incidence was estimated to be 0·56% per year. Forty seven out of 100 pools of 5000 plasma donations tested positive for parvovirus DNA. We inferred that the course of viraemia in asymptomatic donors shows a short peak (>109 copies parvovirus DNA/ml), followed by viraemia below 106 copies/ml for about 2 weeks.