West Nile virus (WNV) is now endemic in the USA. After the widespread surge of virus activity across the USA, research has flourished, and our knowledge base has significantly expanded over the past 10 years since WNV was first recognized in New York City. This article provides a review of the virology of WNV, history, epidemiology, clinical features, pathology of infection, the innate and adaptive immune response, host risk factors for developing severe disease, clinical sequelae following severe disease, chronic infection, and the future of prevention.

West Nile virus (WNV) was detected in Italy, in late summer 2008 in horses and birds in the Po valley. As a consequence, an intense WNV surveillance was implemented in that area involving Emilia-Romagna, Veneto and Lombardy. This paper presents the results of the September 2008–November 2009 surveillance on equines, mosquitoes, wild birds, dogs and cattle in Veneto. WNV was detected in equines and dogs, and, to a lesser extent in cattle and wild birds. Simultaneous circulation of Usutu virus was detected by testing wild birds found dead. Usutu virus but not WNV was also found in mosquitoes monitored during 2009. Equine practices monitoring allowed the definition of an area of WNV circulation and the 2008–2009 westward and northward spread of the infection. Although a relatively low number of human cases and a low virus circulation in vectors and birds detected in Veneto region could be considered favourable conditions for a limited risk of human exposure, it remains difficult to predict the possible evolution of the epidemiological situation.

Vaccination coverage and seroprevalence of poliovirus antibodies were assessed in Argentinean children (aged 8–12 and 19–21 months) living in Cordoba City pre-/post-implementation of a DTwP-IPV-Hib vaccination programme, and compared to those of controls from neighbouring populations receiving a full oral poliovirus vaccine schedule. Vaccination coverage was higher in control areas pre-intervention; this increased post-intervention in Cordoba (>90%) but not in control areas. Poliovirus types 1 and 2 seroprotection rates were >97% in all groups pre-/post-intervention. Type 3 seroprotection rates were generally lower, but increased post-intervention in Cordoba becoming significantly higher than control rates. Anti-type 1 and 3 antibody titres increased twofold and sevenfold, respectively, post-intervention, whereas anti-type 2 antibody titres decreased ~40% in the 8–12 months group. All titres increased in the 19–21 months post-intervention group. The introduction of a three-dose primary DTwP-IPV-Hib schedule maintained protection against poliovirus types 1 and 2, and increased protection against type 3, while vaccine coverage in the study area increased.

We developed an individual-based (IB) model to explore the stochastic attributes of state transitions, the heterogeneity of the individual interactions, and the impact of different network structure choices on the poliovirus transmission process in the context of understanding the dynamics of outbreaks. We used a previously published differential equation-based model to develop the IB model and inputs. To explore the impact of different types of networks, we implemented a total of 26 variations of six different network structures in the IB model. We found that the choice of network structure plays a critical role in the model estimates of cases and the dynamics of outbreaks. This study provides insights about the potential use of an IB model to support policy analyses related to managing the risks of polioviruses and shows the importance of assumptions about network structure.

Japanese encephalitis (JE) is an important arboviral infection of public health concern. There is a significant variation in mortality (10–30%) in JE viral infection. Epidemics of JE have become regular features in the northen states of India. The recent resurgence of the A226V mutation leading to a widespread Chikungunya epidemic motivated the investigators to search for any such mutational occurrence with Japanese encephalitis virus (JEV) isolated from this region. This study looked for mutation of clinical strains at amino-acid positions 176, 177, 227, 244, 264 and 279. A novel mutation S227T was detected corresponding to the loop region of domain II, E gene of JEV in comparison to Indian and other isolates from different parts of the world. Genotype III was found to be circulating in this geographical area. Further studies are required to ascertain its role in JE pathogenesis and vector competency.

Dengue is an emerging arboviral disease and currently poses the greatest arboviral threat to human health. In recent decades, there has been a substantial increase in dengue outbreaks in many parts of the world including India. We performed an in-depth investigation of a major dengue outbreak in Andhra Pradesh, southern India in 2007 by serology, virus isolation, RT–PCR and genotyping. The results revealed an unusual emergence of dengue virus type 4 (DENV-4) along with the prevailing DENV-3. Phylogenetic analysis based on complete envelope gene of 182 globally diverse DENV-4 isolates demonstrated the involvement of a unique clade of genotype I of DENV-4 in the outbreak. This study also demonstrated a clear shift in the dominant serotype from DENV-3 to DENV-4 in India. This is the first report regarding the molecular characterization of Indian isolates of DENV-4, which has the potential to be involved in future outbreaks.

We report a nosocomial outbreak of Crimean-Congo haemorrhagic fever (CCHF) that affected six patients in June 2009 in Ghaem Hospital, Mashhad, Iran, apparently related to one index case. The last four cases were healthcare workers. Infection was spread by percutaneous exposure to two cases, and probably by direct contact with blood, clothes and sheets, to three others. The diagnosis in the two fatal cases was not confirmed virologically. The diagnosis in four cases who survived was confirmed by specific reverse transcription polymerase chain reaction. The patients were treated with ribavirin. In endemic areas, every patient presenting with a febrile haemorrhagic syndrome should be considered to have a viral haemorrhagic fever until proven otherwise. Patients who meet the criteria for probable CCHF should be admitted to hospital and treated with ribavirin. Appropriate isolation precautions should be immediately initiated.

In France, haemorrhagic fever with renal syndrome (HFRS) is endemic along the Belgian border. However, this rodent-borne zoonosis caused by the Puumala virus has recently spread south to the Franche-Comté region. We investigated the space–time distribution of HFRS and evaluated the influence of environmental factors that drive the hantavirus reservoir abundance and/or the disease transmission in this area. A scan test clearly indicated space–time clustering, highlighting a single-year (2005) epidemic in the southern part of the region, preceded by a heat-wave 2 years earlier. A Bayesian regression approach showed an association between a variable reflecting biomass (normalized difference vegetation index) and HFRS incidence. The reasons why HFRS cases recently emerged remain largely unknown, and climate parameters alone do not reliably predict outbreaks. Concerted efforts that combine reservoir monitoring, surveillance, and investigation of human cases are warranted to better understand the epidemiological patterns of HFRS in this area.

The use of shared common water points (WPs) and grazing points (GPs) at two different levels of administrative aggregation (village and kebelle) in a region of the Highlands of Ethiopia was explored by means of a questionnaire survey and social network analysis. Despite GPs being more abundant than WPs (208 and 154, respectively), individual GPs provide more contact opportunities for animals. There was great variability in the contact structure of the selected villages within kebelles for both networks, with this variability being higher in the GP networks for each kebelle. Contrary to the commonly held view that WPs are critical for the potential transmission of infectious diseases, intervention at GPs in the Ethiopian Highlands may have greater impact on contacts and thereby opportunities for transmission of infectious diseases between flocks. Some villages appear naturally at much lower risk of introducing disease. These findings could help the design of surveillance and control activities for directly transmitted infectious diseases.

Pseudomonas aeruginosa is one of the leading nosocomial pathogens. The question of the respective contribution of endogenous and exogenous sources remains controversial. In this study, we shed new light on this issue by means of a multilevel logistic regression analysis which allowed a simultaneous investigation of factors associated with prevalence of patients infected with P. aeruginosa at two levels: patient and healthcare facility (HCF) in the eastern regions of France. A total of 25 533 in-patients from 51 HCFs were included in the analysis. The overall prevalence was 0·37% (range 0–1·65%). Multilevel modelling estimated that <14% of total variability of the outcome variable was explained by differences between HCFs and that after adjusting for patient-level variables, which explained 52% of HCF-level variance, the latter became non-significantly different from zero. A compositional effect (patient factors), rather than a contextual effect (ecological factors), explains heterogeneity of the prevalence of patients infected with P. aeruginosa in the eastern HCFs of France.

EuroRotaNet, a laboratory network, was established in order to determine the diversity of co-circulating rotavirus strains in Europe over three or more rotavirus seasons from 2006/2007 and currently includes 16 countries. This report highlights the tremendous diversity of rotavirus strains co-circulating in the European population during three years of surveillance since 2006/2007 and points to the possible origins of these strains including genetic reassortment and interspecies transmission. Furthermore, the ability of the network to identify strains circulating with an incidence of ⩾1% allowed the identification of possible emerging strains such as G8 and G12 since the beginning of the study; analysis of recent data indicates their increased incidence. The introduction of universal rotavirus vaccination in at least two of the participating countries, and partial vaccine coverage in some others may provide data on diversity driven by vaccine introduction and possible strain replacement in Europe.

Faecal specimens of diarrhoea cases (n=2495, collected between November 2007 and October 2009) from Infectious Diseases and Beliaghata General (ID&BG) Hospital, Kolkata, India, were screened by RT–PCR using specific primers targeting region C of the capsid gene of noroviruses (NoVs) to determine the seasonal distribution and clinical characteristics of NoVs associated with diarrhoea. NoV infection was detected in 78 cases, mostly in children aged <2 years. In 22/78 positive cases, the virus was detected as the sole agent; others were as mixed infections with other enteric pathogens. Sequencing of NVGII strains showed clustering with GII.4 NoVs followed by GII.13 and GII.6 NoVs. Clinical characteristics of the diarrhoeic children and adults in Kolkata indicated that NoV infections were detected throughout the year and were associated with a mild degree of dehydration.

Acute diarrhoea remains a major public health challenge in developing countries. We examined the role of a probiotic in the prevention of acute diarrhoea to discover if there was an effect directed towards a specific aetiology. A double-blind, randomized, controlled field trial involving 3758 children aged 1–5 years was conducted in an urban slum community in Kolkata, India. Participants were given either a probiotic drink containing Lactobacillus casei strain Shirota or a nutrient drink daily for 12 weeks. They were followed up for another 12 weeks. The primary outcome of this study was the occurrence of first episodes of diarrhoea. We assessed this during 12 weeks of intake of study agent and also for 12 weeks of follow-up. There were 608 subjects with diarrhoea in the probiotic group and 674 subjects in the nutrient group during the study period of 24 weeks. The level of protective efficacy for the probiotic was 14% (95% confidence interval 4–23, P<0·01 in adjusted model). The reduced occurrence of acute diarrhoea in the probiotic group compared to nutrient group was not associated with any specific aetiology. No adverse event was observed in children of either probiotic or nutrient groups. The study suggests that daily intake of a probiotic drink can play a role in prevention of acute diarrhoea in young children in a community setting of a developing country.

Infectious gastroenteritis is a common illness in Australia as elsewhere. Data from a year-long national gastroenteritis survey in 2001–2002 showed that gastroenteritis was more common in the northern and hotter part of Australia. These data were used to quantify associations between local weather variables and gastroenteritis in people aged >5 years while controlling for socioeconomic status. A distributed lag model was used to examine the influence of weather over a period of days prior to an event and the maximal effect was found at a lag of 2–5 days. The total effect over the preceding week indicated a relative increase from baseline in the probability of gastroenteritis of 2·48% (95% CI 1·01–3·97) for each degree rise (°C) over that period. Given the very high burden of gastroenteritis, this represents a substantial effect at the population level and has relevance for health predictions due to climate change.

This paper describes morbidity and mortality parameters for Campylobacter spp., Salmonella spp., enterohaemorrhagic Escherichia coli, Listeria spp., norovirus infections and their primary associated sequelae [Guillain–Barré syndrome (GBS), haemolytic uraemic syndrome, reactive arthropathies and Reiter's syndrome]. Data from a period of 4 years were obtained from three national databases to estimate percentage of reported cases hospitalized, mean annual hospitalization incidence rate, frequency of hospitalization by age and sex, and number of deaths. The length of hospital stay, discharge disposition, hospitalization age, and number of diagnoses per case were also extracted and summarized. In addition, we estimated that each year in Canada, there are between 126 and 251 cases of Campylobacter-associated GBS. This study provides morbidity and mortality estimates for the top enteric pathogens in Canada, including their associated sequelae, which can contribute to the quantification of the burden of illness.

A cross-sectional study was conducted to investigate risk factors for sporadic Cryptosporidium infection in a paediatric population in Nigeria. Of 692 children, 134 (19·4%) were infected with Cryptosporidium oocysts. Cryptosporidium spp. were identified in 49 positive samples using PCR–restriction fragment length polymorphism and direct sequencing of the glycoprotein60 (GP60) gene. Generalized linear mixed-effects models were used to identify risk factors for all Cryptosporidium infections, as well as for C. hominis and C. parvum both together and separately. Risk factors identified for all Cryptosporidium infections included malaria infection and a lack of Ascaris infection. For C. hominis infections, stunting and younger age were highlighted as risk factors, while stunting and malaria infection were identified as risk factors for C. parvum infection.

Past studies exploring risk factors for fluoroquinolone (FQ) resistance in urinary tract infections (UTIs) focused only on UTIs caused by Gram-negative pathogens. The epidemiology of FQ resistance in enterococcal UTIs has not been studied. We conducted a case-control study at two medical centres within the University of Pennsylvania Health System in order to identify risk factors for FQ resistance in enterococcal UTIs. Subjects with positive urine cultures for enterococci and meeting CDC criteria for healthcare-acquired UTI were eligible. Cases were subjects with FQ-resistant enterococcal UTI. Controls were subjects with FQ-susceptible enterococcal UTI and were frequency matched to cases by month of isolation. A total of 136 cases and 139 controls were included from 1 January 2003 to 31 March 2005. Independent risk factors [adjusted OR (95% CI)] for FQ resistance included cardiovascular diseases [2·24 (1·05–4·79), P=0·037], hospitalization within the past 2 weeks [2·08 (1·05–4·11), P=0·035], hospitalization on a medicine service [2·15 (1·08–4·30), P<0·030], recent exposure to β-lactamase inhibitors (BLIs) [14·98 (2·92–76·99), P<0·001], extended spectrum cephalosporins [9·82 (3·37–28·60), P<0·001], FQs [5·36 (2·20–13·05), P<0·001] and clindamycin [13·90 (1·21–10·49), P=0·035]. Use of BLIs, extended spectrum cephalosporins, FQs and clindamycin was associated with FQ resistance in enterococcal uropathogens. Efforts to curb FQ resistance should focus on optimizing use of these agents.

Rubella, a mild, vaccine-preventable disease, can manifest as congenital rubella syndrome (CRS), a devastating disease of the fetus. To emphasize the inadequacy of the existing rubella vaccination programme in India, we evaluated epidemiological evidence of rubella virus activity with data available from a tertiary-care centre. The proportion of suspected CRS cases that were laboratory confirmed increased from 4% in 2000 to 11% in 2008. During the same period, 329 clinically suspected postnatal rubella cases were tested of which 65 (20%) were laboratory confirmed. Of women (n=770) of childbearing age, 12·5% were susceptible to rubella.