We investigated the epidemic pattern of chickenpox incidence among 47 prefectures in Japan. There were two peaks in chickenpox incidence in all prefectures. The first peaks appear at almost the same time in a year, while the second peaks occur at different times with relatively different types of size and shape. The feature of the second peak might characterize the epidemic pattern of chickenpox. We first introduced the second peak index, that is, the ratio of the difference between the incidence at the point of the second peak and the minimum incidence between the first and second peaks to the difference between the incidence at the point of the second peak and the minimum incidence in the year. There was a close correlation between the second peak index and the magnitude of variation in temperature within a year corresponding to the difference between the maximum and the minimum of the monthly mean of the highest daily temperature. This is the first article focusing on the close relationship between the second peak of epidemic pattern of chickenpox incidence and the variation of temperature within a year.

Staphylococcus aureus is the most prevalent pathogen causing mastitis of dairy ruminants. This study was developed to ascertain the genotypes and genealogical relationship among strains isolated from milk of bovines with mastitis in Argentina. Molecular epidemiological analysis of S. aureus was performed on 112 isolates from 21 districts. Clonality was assessed by SmaI pulsed-field gel electrophoresis (PFGE) typing, automated EcoRI ribotyping and restriction enzyme analysis of plasmid (REAP) DNA profiles. A total of 22 band patterns distributed in four clusters were found by SmaI PFGE analysis. The similarity of clusters 2, 3 and 4 with cluster 1 was 0·73, 0·69 and 0·33, respectively, and 101 of 112 isolates belonged in cluster 1. PFGE band patterns from 42 isolates within cluster 1 were indistinguishable from each other (type A). The second largest group of isolates with indistinguishable PFGE band patterns was subtype A11, which was composed of 19 isolates. Automated ribotyping assigned the 112 isolates into 13 ribotypes. Among these, the most prevalent ribotypes I and VI were composed of 49 and 35 isolates respectively. Although there was certain correspondence between PFGE genotypes and ribotypes, further discrimination was achieved by combining both methods. REAP DNA profile analysis was useful to provide even further discrimination between isolates with identical PFGE genotype and ribotype. The most prevalent S. aureus strains A/I and A11/VI were widely distributed in the country and were not restricted to individual nearby locations. Prevalence of these two strains varied consecutively within a period of 8 years. Whether the shift in type prevalence was due to selection of a phenotypic trait remains undisclosed.

Deterministic models were employed to investigate the biology of Trypanosoma evansi infection in the Indonesian buffalo. Models were fitted to two age-structured data sets of infection. The Susceptible–Infected–Susceptible (SIS) model was the best supported description of this infection, although the results of the analysis depended on the serological test used: the Tr7 Ag-ELISA was judged the most reliable indicator of infection. Estimated forces of infection increase with age from 1·2 to 2·0 acquisitions per buffalo per year. The buffaloes would clear infection in an estimated mean time period of 16·8 months (95% CIs: 12·5–25·9 months) since acquisition, either by drug treatment by owners or self-cure. A general discussion on the role of immunity in protozoan infections includes consideration that the fitted SIS model would be consistent with strain-specific immunity. The model may become a useful tool for the evaluation of control programmes.

African swine fever (ASF) suspected clinically in Madagascar (1998–9) was confirmed by polymerase chain reaction (PCR) and nucleotide sequencing, following virus isolation. No haemadsorption or cytopathic effect could be detected following leukocyte inoculation, but viral growth in cells was confirmed by PCR. Detection of ASF virus genome was carried out by amplification of a highly conserved region coding for the p72 protein. Nucleotide sequencing of the amplicon revealed 99·2% nucleotide identity between the recent Malagasy strains and a virus recovered from the 1994 outbreak in Mozambique (SPEC265). A serological survey performed on 449 sera, revealed that only 5·3% of the sera taken from pigs between 1998 and 1999 were positive.

Varicella is one of the most common childhood diseases. The course of the disease is usually mild and uncomplicated. In Slovenia, varicella is a notifiable communicable disease which must be reported. Data collected from 1979–98 were analysed. Over the 20-year period the number of varicella cases reported ranged from a low of 11 086 (in 1994) to a maximum of 21 141 (in 1987). During the last 10 years, the highest incidence of varicella was reported in children aged from 12 months to 2 years. In adults over 20, incidence has slightly but steadily increased over the 20 year period. Overall, the number of males with varicella exceeded that of females. The proportion of females was higher only in the 20–30-year age group, probably as a consequence of more frequent and closer contact with infected children by mothers. The highest number of reported cases was during winter and early spring.

We describe a major outbreak of pseudorabies virus (PRV) in a sow herd in which the sows were vaccinated simultaneously three times a year with a vaccine containing Bartha strain. Also in the associated rearing herd in which the gilts were vaccinated twice an outbreak of PRV occurred. The outbreak was analysed with mathematical models, statistical methods and Monte-Carlo simulation. Under the assumption that the outbreak started with one introduction of virus the reproduction ratio Rind – as a measure of transmission of PRV between individuals – in the sow herd was estimated with a Generalized Linear Model to be 1·6. Also under the assumption of one introduction of virus Rind in the rearing herd was estimated with a martingale estimator to be 1·7. Both estimates were significantly larger than 1. Mathematical analysis showed that heterogeneity in the sow herd, because of the presence of not-optimally immunized replacement sows could not be the only cause of the observed outbreak in the sow herd. With Monte-Carlo simulations, the duration of an outbreak after a single introduction of virus and Rind = 1·6 did not mimic the data and thus the hypothesis of a single introduction with Rind = 1·6 could also be rejected and Rind is thus, not necessarily above 1. Moreover, with statistical analysis, endemicity in the combination of herds as a cause for the observed outbreak could be rejected. Endemicity in the rearing herd alone could not be excluded. Therefore, multiple introductions from outside and most probably from the rearing herd were possibly the cause of the observed outbreak(s). The implications for eradication of pseudorabies virus were discussed.

This multi-centre, cross-sectional study was designed to reveal the present status of hepatitis B infection markers among Lebanese children, and provide recommendations regarding childhood immunization policies. A total of 841 children, aged between 6 months and 6·5 years, were enrolled from Lebanon's five districts. Their sera were tested for hepatitis B surface antigen and hepatitis B core IgG. The overall prevalence of hepatitis B virus infection markers was 0·8 % with increasing age-specific rates from 0 % at 6 months to 1·3 % at > 5 years. There was no statistically significant association between the presence of hepatitis B markers and family characteristics or risk factors for infection. The highest prevalence rates were among children from Beirut suburbs (2·9 %) and South Lebanon (1·6 %). The risk of horizontal transmission of hepatitis B to uninfected children increased substantially after the age of 2 years. An expanded programme on immunization that integrates hepatitis B vaccine during the first year of life is needed.

This study evaluated the roles of multiple factors in hepatitis C virus (HCV) infection, with emphasis on the modification of various individual characteristics on the risk associated with percutaneous exposure to blood. Serum samples taken from 4869 men in Taiwan within a cohort study were tested for HCV antibody. The overall positive rate of anti-HCV was 1·6 %. In a logistic regression, factors positively associated with anti-HCV positivity were previous blood transfusion (odds ratio [OR] = 7·28; 95 % confidence interval [CI] = 4·26–12·45), a history of surgery (OR = 2·06; 95 % CI = 1·23–3·46), and lower educational levels (OR = 1·94; 95 % CI = 1·14–3·32). The anti-HCV positive rate was significantly lower in hepatitis B surface antigen (HBsAg) carriers than in non-carriers (OR = 0·60; 95 % CI = 0·37–0·95). Ageing, lower educational levels, O blood group, and Taiwanese ethnicity enhanced the likelihood of HCV infection through blood transfusion/surgery, whereas HBsAg status, cigarette smoking, and habitual alcohol drinking reduced it.

Shiga toxin-producing Escherichia coli (STEC) O157 was investigated with respect to its halotolerance and whether it can survive in marine water. STEC O157 could multiply in a medium containing 5% NaCl and in sterilized marine water, and could survive in unsterilized marine water for at least 15 days. On the basis of these results, we postulated that STEC O157 may survive in natural marine water, and attempted to isolate the bacterium and Shiga toxin gene (stx) from marine water in Japan. The stx, comprising stx1 and stx2, was detected from marine water samples by PCR. STEC and other stx-positive bacteria, however, could not be isolated from these samples in this study. These results indicate that stx-positive bacteria may survive in marine water and suggest the necessity of a survey.

In 1996, serological responses to two Cryptosporidium antigens were determined for 200 Las Vegas (LV), Nevada, and 200 Albuquerque, New Mexico, blood donors to evaluate associations between endemic infections, water exposures, and other risk factors. LV uses chlorinated filtered drinking water from Lake Mead while Albuquerque uses chlorinated ground water. The intensity of serological response to both markers was higher for older donors (P < 0·05), donors who washed food with bottled water (P < 0·05) and donors from LV (P < 0·05). A decreased serological response was not associated with bottled water consumption, nor was an increased response associated with self-reported cryptosporidiosis-like illness or residence in LV at the time of a cryptosporidiosis outbreak 2 years earlier. Although these findings suggest the serological response may be associated with type of tap water and certain foods, additional research is needed to clarify the role of both food and drinking water in endemic Cryptosporidium infection.

An outbreak of E. coli O157 infection occurred in the Highland Region of Scotland in the summer of 1999. The source of the outbreak was traced to an untreated private water supply. All six cases identified arose in visitors to the area, and most had very limited exposure to the contaminated water. Permanent residents on the same supply were unaffected. The E. coli O157 isolates from the water, sheep faeces collected from around the source and the human stool samples were indistinguishable using pulsed field gel electrophoresis. Previously reported outbreaks of E. coli O157 linked to potable water supplies have resulted from structural or treatment failures, which allowed faecal contamination of source water. Here, contamination of the water supply and subsequent human infection was due to the use of an untreated, unprotected private water source in a rural area where animals grazed freely.

In epidemiological studies of infectious disease, researchers often rely on specific cues of the host, such as clinical signs, as surrogate indicators of pathogen presence. A selection bias would manifest if the specific visual cues used in sampling for the pathogen were not representative of the full range of signs caused by the strains of that pathogen. In our molecular epidemiological studies of Escherichia coli associated with avian cellulitis in broilers, we collect carcasses at the processing plant based on visual cues of lesion morphology. Therefore, the objectives of this study were to: (1) explore the potential impacts of selection bias in an application of infectious disease epidemiology, and (2) utilize a validation protocol to assess the potential for selection bias in our molecular epidemiological studies of E. coli and avian cellulitis. In two different trials, E. coli DNA fingerprints were compared between birds that our observers collected and the birds that the observers missed. Using Fisher's exact tests and simulation models, we determined that the isolates collected by the observers were not significantly different from the isolates missed by the observers (P>0·60 in both trials). Our method of selecting birds suspected of having cellulitis did not significantly bias our inferences about the population of E. coli associated with cellulitis in the flock. We encourage more investigators to critically assess the relationship of the sample to the target population in epidemiological studies of infectious disease.

The natural habitat of Paracoccidioides brasiliensis, agent of paracoccidioidomycosis (PCM), remains unknown. This study is aimed at establishing associations between the ecological variables present in all Colombian municipalities and the incidence of PCM. Records of 940 patients were studied and several ecological variables analysed, as well as their association to amount of patients per total rural population in each municipality, determined through a multivariate analysis. All 940 patients came from 216 municipalities (20·3 %), out of which, 93 were birthplace and place of long-term residence for 121 patients. The Incidence Rate Ratio (IRR) was determined for these 93 municipalities. The following variables fitted the model: altitude from 1000 to 1499 metres above sea level (IRR = 6·37), rainfall from 2000 to 2999 mm (IRR = 2·15), presence of humid forests (Holdridge) (IRR = 1·79) and coffee (IRR = 1·95), tobacco (IRR = 3·59) crops. These results indicate that these municipalities constitute reservareas for P. brasiliensis (Borelli).

Aedes aegypti female mosquitoes are capable of the mechanical transmission of lumpy skin disease virus (LSDV) from infected to susceptible cattle. Mosquitoes that had fed upon lesions of LSDV-infected cattle were able to transmit virus to susceptible cattle over a period of 2–6 days post-infective feeding. Virus was isolated from the recipient animals in 5 out of 7 cases. The clinical disease recorded in the animals exposed to infected mosquitoes was generally of a mild nature, with only one case being moderate. LSDV has long been suspected to be insect transmitted, but these findings are the first to demonstrate this unequivocally, and they suggest that mosquito species are competent vectors.

Outbreaks of Legionnaire's disease present a public health challenge especially because fatal outcomes still remain frequent. The aim of this study was to describe the abundance and epidemiology of Legionellaceae in the human-made environment. Water was sampled from hot- water taps in private and public buildings across the area of Göttingen, Germany, including distant suburbs. Following isolation, we used polymerase chain reaction in order to generate strain specific banding profiles of legionella isolates. In total, 70 buildings were examined. Of these 18 (26%) had the bacterium in at least one water sample. Legionella pneumophila serogroups 1, 4, 5 and 6 could be identified in the water samples. Most of the buildings were colonized solely by one distinct strain, as proven by PCR. In three cases equal patterns were found in separate buildings. There were two buildings in this study where isolates with different serogroups were found at the same time.

The prevalence of parapoxvirus infection was examined in free-ranging wild ruminants in Japan, Japanese serow (Capricornis crispus) and Japanese deer (Cervus nippon centralis), in 1996–9. We collected a total of 151 serum samples from 101 Japanese serows and 50 Japanese deer and tested for antibodies against parapoxvirus by an enzyme-linked immunosorbent assay and an agar gel immunodiffusion test. Overall seroprevalences among Japanese serows were 5/25 (20·0%) in 1996, 4/14 (28·6%) in 1997, 5/32 (15·6%) in 1998 and 2/30 (6·7%) in 1999, respectively. The seroprevalence increased with age but was not affected by sex. No antibodies were detected from any of 50 serum samples taken from Japanese deer. Our results in this study suggest that parapoxvirus infection is widespread among the population of Japanese serows, however, Japanese deer appear to be still free of the disease.