Most studies describing high rates of acute respiratory illness in aboriginals have focused on rural or remote communities. Hypothesized causes include socioeconomic deprivation, limited access to healthcare, and a high prevalence of chronic disease. To assess influenza rates in an aboriginal community while accounting for healthcare access, deprivation and chronic disease prevalence, we compared rates of influenza-related outpatient and emergency-department visits in an urban Mohawk reserve (Kahnawá:ke) to rates in neighbouring regions with comparable living conditions and then restricted the analysis to a sub-population with a low chronic disease prevalence, i.e. those aged <20 years. Using medical billing claims from 1996 to 2006 we estimated age-sex standardized rate ratios. The rate in Kahnawá:ke was 58% greater than neighbouring regions and 98% greater in the analysis of those aged <20 years. Despite relatively favourable socioeconomic conditions and healthcare access, rates of influenza-related visits in Kahnawá:ke were elevated, particularly in the younger age groups.
A central tenet of close-contact or respiratory infection epidemiology is that infection patterns within human populations are related to underlying patterns of social interaction. Until recently, few researchers had attempted to quantify potentially infectious encounters made between people. Now, however, several studies have quantified social mixing behaviour, using a variety of methods. Here, we review the methodologies employed, suggest other appropriate methods and technologies, and outline future research challenges for this rapidly advancing field of research.
Contact diary; infectious disease control; mathematical modelling; proximity; social mixing; social network; transmission
We studied seasonal patterns of swine hepatitis E virus (HEV) infection in China. From 2008 through 2011, 4200 swine bile specimens were collected for the detection of HEV RNA. A total of 3.83% (92/2400) of specimens in eastern China and 2.61% (47/1800) in southwestern China were positive for HEV. Seasonal patterns differing by geographical area were suggested. In eastern China, the major peak of HEV RNA prevalence was during March-April, with a minor peak during September-October, and a dip during July-August. In southwestern China, the peak was during September-October and the dip during March-April. The majority of subtype 4a cases (76.83%, 63/82) were detected in the first half of the year, while the majority of subtype 4b cases (89.66%, 26/29) were concentrated in the second half of the year, suggesting different subtype contribute to different peaks. Our results indicate that the distribution of HEV subtypes is associated with seasonal patterns.
There are limited data examining whether outcomes of MRSA healthcare-associated infections (HAIs) are worse when caused by community-associated strains compared to healthcare-associated strains. We reviewed all patient charts at our institution from 1999 to 2009 that had MRSA first isolated only after 72 hours of hospitalization (n=724). Of these, 384 patients had an MRSA-HAI by CDC criteria. Treatment failure was similar in those infected with a phenotypically CA-MRSA strain compared to a phenotypically HA-MRSA strain (23% vs. 15%, P=0.10) as was 30-day mortality (16% vs. 19%, P=0.57). Independent risk factors associated with (p<0.05) treatment failure were higher Charlson Comorbidity Index, higher APACHE II score, and no anti-MRSA treatment. These factors were also associated with 30-day mortality, as were female gender, older age, MRSA bloodstream infection, MRSA pneumonia, and HIV. Our findings suggest that clinical and host factors, not MRSA strain type, predict treatment failure and death in hospitalized patients with MRSA-HAIs.
MRSA; healthcare-associated; community-associated; outcomes; genotype
This study investigates neighbourhood variation in rates of pneumococcal bacteraemia and community-level factors associated with neighbourhood heterogeneity in disease risk. We analysed data from 1416 adult and paediatric cases of pneumococcal bacteraemia collected during 2005–2008 from a population-based hospital surveillance network in metropolitan Philadelphia. Cases were geocoded using residential address to measure disease incidence by neighbourhood and identify potential neighbourhood-level risk factors. Overall incidence of pneumococcal bacteraemia was 36·8 cases/100 000 population and varied significantly (0–67·8 cases/100 000 population) in 281 neighbourhoods. Increased disease incidence was associated with higher population density [incidence rate ratio (IRR) 1·10/10 000 people per mile2, 95% confidence interval (CI) 1·0–1·19], higher percent black population (per 10% increase) (IRR 1·07, 95% CI 1·04–1·09), population aged ≤5 years (IRR 3·49, CI 1·8–5·18) and population aged ≥65 years (IRR 1·19, CI 1·00–1·38). After adjusting for these characteristics, there was no significant difference in neighbourhood disease rates. This study demonstrates substantial small-area variation in pneumococcal bacteraemia risk that appears to be explained by neighbourhood sociodemographic characteristics. Identifying neighbourhoods with increased disease risk may provide valuable information to optimize implementation of prevention strategies.
Geographic information systems; neighbourhood risk factors; pneumococcal disease
Causal mechanisms of norovirus outbreaks are often not revealed. Understanding the transmission route (e.g., foodborne, waterborne, or environmental) and vehicle (e.g., shellfish or recreational water) of a norovirus outbreak, however, is of great public health importance; this information can facilitate interventions for an ongoing outbreak and regulatory action to limit future outbreaks. Towards this goal, we conducted a systematic review to examine whether published outbreak information was associated with the implicated transmission route or vehicle. Genogroup distribution was associated with transmission route and food vehicle, but attack rate and the presence of GII.4 strain were not associated with transmission route, food vehicle, or water vehicle. Attack rate, genogroup distribution, and GII.4 strain distribution also varied by other outbreak characteristics (e.g. setting, season, and hemisphere). These relationships suggest that different genogroups exploit different environmental conditions and thereby can be used to predict the likelihood of various transmission routes or vehicles.
The impact of human metapneumovirus (HMPV) in children older than 5 years of age and the risk factors associated with disease severity for all ages have not been well characterized. A retrospective cohort study of 238 children 0–15 years hospitalized over a 3-year period was performed. Medical records were reviewed for demographic, clinical parameters and outcomes. Multivariable analyses were performed to identify independent factors associated with worse disease severity assessed by length of hospitalization (LOS), need for ICU care, respiratory support, and a disease severity score. Pulmonary diseases were associated with all outcomes of care, while congenital heart disease (CHD) and neuromuscular disorders were associated with longer LOS, and CHD and trisomy 21 were associated with worse severity scores independent of other covariables. Fever, retractions, use of steroids and albuterol were also associated with enhanced disease severity. Understanding the determinants of HMPV disease in children may help design targeted preventive strategies.
In Finland, the pandemic influenza virus A(H1N1)pdm09 was the dominant influenza strain during the pandemic season in 2009/2010 and presented alongside other influenza types during the 2010/2011 season. The true number of infected individuals is unknown, as surveillance missed a large portion of mild infections. We applied Bayesian evidence synthesis, combining available data from the national infectious disease registry with an ascertainment model and prior information on A(H1N1)pdm09 influenza and the surveillance system, to estimate the total incidence and hospitalization rate of A(H1N1)pdm09 infection. The estimated numbers of A(H1N1)pdm09 infections in Finland were 211 000 (4% of the population) in the 2009/2010 pandemic season and 53 000 (1% of the population) during the 2010/2011 season. Altogether, 1·1% of infected individuals were hospitalized. Only 1 infection per 25 was ascertained.
A(H1N1)pdm09; Bayesian analysis; influenza; mathematical modelling
Antimicrobial resistance is a priority emerging public health threat, and the ability to detect promptly outbreaks caused by resistant pathogens is critical for resistance containment and disease control efforts. We describe and evaluate the use of an electronic laboratory data system (WHONET) and a space–time permutation scan statistic for semi-automated disease outbreak detection. In collaboration with WHONET-Argentina, the national network for surveillance of antimicrobial resistance, we applied the system to the detection of local and regional outbreaks of Shigella spp. We searched for clusters on the basis of genus, species, and resistance phenotype and identified 19 statistical ‘events’ in a 12-month period. Of the six known outbreaks reported to the Ministry of Health, four had good or suggestive agreement with SaTScan-detected events. The most discriminating analyses were those involving resistance phenotypes. Electronic laboratory-based disease surveillance incorporating statistical cluster detection methods can enhance infectious disease outbreak detection and response.
Antibiotic resistance; medical informatics; outbreaks; Shigella; surveillance
Recent discovery of genetically distinct hantaviruses in shrews and moles (order Soricomorpha, family Soricidae and Talpidae) has challenged the conventional view that rodents serve as the principal reservoir hosts. Nova virus (NVAV), previously identified in archival liver tissue of a single European mole (Talpa europaea) from Hungary, represents one of the most highly divergent hantaviruses identified to date. To ascertain the spatial distribution and genetic diversity of NVAV, we employed RT–PCR to analyse lungs from 94 moles, captured in two locations in France, during October 2012 to March 2013. NVAV was detected in more than 60% of moles at each location, suggesting efficient enzootic virus transmission and confirming that this mole species serves as the reservoir host. Although the pathogenic potential of NVAV is unknown, the widespread geographical distribution of the European mole might pose a hantavirus exposure risk for humans.
France; hantavirus; mole; phylogeny; Talpa
Methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia cause significant morbidity and mortality in hospitalized patients. Using a nested case-control design, 204 MRSA bacteraemia cases were compared to 301 unmatched methicillin-susceptible Staphylococcus aureus (MSSA) bacteraemia controls and were matched 1:2 with non-infected controls. The independent risk factors for MRSA bacteraemia compared to MSSA bacteraemia were older age (P=0·048), major organ transplant during current hospital stay (P=0·016) and quinolone use (P=0·016). Cases were more likely than non-infected controls to have renal failure (P=0·003), cirrhosis (P=0·013), and a central venous catheter (P=0·003) after controlling for other risk factors. This large case-control study made it possible to assess risk factors for MRSA bacteraemia using two sets of controls and showed that risk factors differed greatly depending on the control group chosen. These results confirm the need for careful selection of appropriate control groups and the need to carefully adjust for underlying severity of illness.
Antibiotic resistance; bacteraemia; methicillin-resistant Staphylococcus aureus; multidrug-resistant infections
Human campylobacteriosis exhibits a distinctive seasonality in temperate regions. This paper aims to identify the origins of this seasonality. Clinical isolates [typed by multi-locus sequence typing (MLST)] and epidemiological data were collected from Scotland. Young rural children were found to have an increased burden of disease in the late spring due to strains of non-chicken origin (e.g. ruminant and wild bird strains from environmental sources). In contrast the adult population had an extended summer peak associated with chicken strains. Travel abroad and UK mainland travel were associated with up to 17% and 18% of cases, respectively. International strains were associated with chicken, had a higher diversity than indigenous strains and a different spectrum of MLST types representative of these countries. Integrating empirical epidemiology and molecular subtyping can successfully elucidate the seasonal components of human campylobacteriosis. The findings will enable public health officials to focus strategies to reduce the disease burden.
Bacterial typing; Campylobacter; foodborne zoonoses; modelling; molecular epidemiology
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.
Enterococci; fluoroquinolone resistance; urinary tract infection
The incidence of myocardial infarctions and influenza follow similar seasonal patterns. To determine if acute myocardial infarctions (AMIs) and ischemic strokes are associated with influenza activity, we built time series models using data from the Nationwide Inpatient Sample. In these models, we used influenza activity to predict the incidence of AMI and ischemic stroke. We fit national models as well as models based on four geographic regions and five age groups. Across all models, we found consistent significant associations between AMIs and influenza activity, but not between ischemic strokes and influenza. Associations between influenza and AMI increased with age, were greatest in those over 80 years old, and were present in all geographic regions. In addition, the natural experiment provided by the second wave of the influenza pandemic in 2009 provided further evidence of the relationship between influenza and AMI, because both series peaked in the same non-winter month.
acute myocardial infarction; ischemic stroke; influenza; pandemic
To assess the prevalence and risk factors for colonization with Staphylococcus aureus in inmates entering two maximum-security prisons in New York State, USA, inmates (N=830) were interviewed and anterior nares and oropharyngeal samples collected. Isolates were characterized using spa typing. Overall, 50·5% of women and 58·3% of men were colonized with S. aureus and 10·6% of women and 5·9% of men were colonized with MRSA at either or both body sites. Of MSSA isolates, the major subtypes were spa type 008 and 002. Overall, risk factors for S. aureus colonization varied by gender and were only found in women and included younger age, fair/poor self-reported general health, and longer length of prior incarceration. Prevalence of MRSA colonization was 8·2%, nearly 10 times greater than in the general population. Control of epidemic S. aureus in prisons should consider the constant introduction of strains by new inmates.
Estimating; methicillin-resistant Staphylococcus aureus (MRSA); molecular epidemiology; prevalence of disease; risk assessment; Staphylococcus aureus
This paper examines whether previously identified community-level factors (high proportion of crowded households and/or persons below the poverty level) remain associated with childhood pneumococcal carriage in the heptavalent pneumococcal conjugate vaccine (PCV7) era. Using logistic regression, individual factors were used to develop base models to which community-level factors were added to evaluate impact on pneumococcal carriage within two pediatric study cohorts from Massachusetts (urban Boston, outside Boston). Six years after introduction of universal childhood PCV7 vaccination, we found no consistent evidence that census tract characteristics (e.g. population size and density, age and race distribution, percent participating in group child care, parental education, percent lacking in-unit plumbing, poverty, and community stability) affected odds of pneumococcal carriage when added to individual predictors (e.g. younger age, current respiratory tract infections, and attendance in group child care). How community-level factors influence carriage continues to change in the era of increasing immunization coverage.
Streptococcus pneumoniae; pneumococcal conjugate vaccine; colonization; community risk factors
The factors underlying the temporal dynamics of rubella outside of Europe and North America are not well known. Here we used 20 years of incidence reports from Mexico to identify variation in seasonal forcing and magnitude of transmission across the country and to explore determinants of inter-annual variability in epidemic magnitude in rubella. We found considerable regional variation in both magnitude of transmission and amplitude of seasonal variation in transmission. Several lines of evidence pointed to stochastic dynamics as an important driver of multi-annual cycles. Since average age of infection increased with the relative importance of stochastic dynamics, this conclusion has implications for the burden of congenital rubella syndrome. We discuss factors underlying regional variation, and implications of the importance of stochasticity for vaccination implementation.
Analysis of data; epidemiology; rubella; statistics
Vancomycin-resistant Enterococcus bloodstream infections (VRE-BSI) are a growing problem with few clinical trials to guide therapy. We conducted a retrospective study of management and predictors of mortality for VRE-BSI at a tertiary care centre from January 2005 to August 2008. Univariate and multivariable analyses examined the relationship of patient characteristics and antibiotic therapy with 30-day all-cause mortality. Rates of VRE-BSI increased from 0.06 to 0.17 infections/thousand patient days (p=0.03). Among 235 patients, 30-day mortality was 34.9%. Patients were primarily treated with linezolid (44.2%) or daptomycin (36.5%). Factors associated with mortality were haemodialysis (OR 3.2, 95% CI 1.6-6.3, p=0.007), mechanical ventilation (OR 3.7, 95% CI 1.3-10.4, p=0.01), and malnutrition (OR 2.0, 95% CI 1.0-4.0, p=0.046). Use of linezolid, but not daptomycin (p=0.052) showed a trend toward an association with survival. In conclusion, VRE-BSI is a growing problem, associated with significant 30-day mortality. Multiple factors were associated with poor outcomes at our hospital.
Reduced vancomycin susceptibility (RVS) may lead to poor clinical outcomes in Staphylococcus aureus bacteraemia. We conducted a cohort study of 392 patients with S. aureus bacteraemia within a university health system. The association between RVS, as defined by both Etest [vancomycin minimum inhibitory concentration (MIC) > 1.0 µg/ml] and broth microdilution (vancomycin MIC ≥ 1.0 µg/ml), and patient and clinical variables were evaluated to create separate predictive models for RVS. In total, 134 (34.2%) and 73 (18.6%) patients had S. aureus isolates with RVS by Etest and broth microdilution, respectively. The final model for RVS by Etest included methicillin resistance [odds ratio (OR) 1.51, 95% confidence interval (CI) 0.97–2.34], non-white race (OR 0.67, 95% CI 0.42–1.07), healthcare-associated infection (OR 0.56, 95% CI 0.32–0.96), and receipt of any antimicrobial therapy ≤ 30 days prior to the culture date (OR 3.06, 95% CI 1.72–5.44). The final model for RVS by broth microdilution included methicillin resistance (OR 2.45, 95% CI 1.42–4.24), admission through the emergency department (OR 0.54, 95% CI 0.32–0.92), presence of an intravascular device (OR 2.24, 95% CI 1.30–3.86), and malignancy (OR 0.51, 95% CI 0.26–1.00). The availability of an easy and rapid clinical prediction rule for early identification of RVS can be used to help guide the timely and individualized management of these serious infections.
Hospital-acquired (nosocomial) infections; infectious disease epidemiology; methicillin-resistant S. aureus (MRSA); Staphylococcus aureus
Infectious mononucleosis is a clinical manifestation of primary Epstein–Barr virus infection. It is unknown whether genetic factors contribute to risk. To assess heritability, we compared disease concordance in monozygotic to dizygotic twin pairs from the population-based California Twin Program and assessed the risk to initially unaffected co-twins. One member of 611 and both members of 58 twin pairs reported a history of infectious mononucleosis. Pairwise concordance in monozygotic and dizygotic pairs was respectively 12·1% [standard error (s.e.)=1·9%] and 6·1% (s.e.=1·2%). The relative risk (hazard ratio) of monozygotic compared to dizygotic unaffected co-twins of cases was 1·9 [95% confidence interval (CI) 1·1–3·4, P=0·03], over the follow-up period. When the analysis was restricted to same-sex twin pairs, that estimate was 2·5 (95% CI 1·2–5·3, P=0·02). The results are compatible with a heritable contribution to the risk of infectious mononucleosis.
Epstein–Barr virus; genetics; infectious mononucleosis; twins
Throughout the African meningitis belt, meningococcal meningitis outbreaks occur only during the dry season. Measles in Niger exhibits similar seasonality, where increased population density during the dry season likely escalates measles transmission. Because meningococcal meningitis and measles are both directly transmitted, we propose that host aggregation also impacts the transmission of meningococcal meningitis. Although climate affects broad meningococcal meningitis seasonality, we focus on the less examined role of human density at a finer spatial scale. By analysing spatial patterns of suspected cases of meningococcal meningitis, we show fewer absences of suspected cases in districts along primary roads, similar to measles fadeouts in the same Nigerien metapopulation. We further show that, following periods during no suspected cases, districts with high reappearance rates of meningococcal meningitis also have high measles reintroduction rates. Despite many biological and epidemiological differences, similar seasonal and spatial patterns emerge from the dynamics of both diseases. This analysis enhances our understanding of spatial patterns and disease transmission and suggests hotspots for infection and potential target areas for meningococcal meningitis surveillance and intervention.
Economic analyses of cholera immunization programmes require estimates of the costs of cholera. The Diseases of the Most Impoverished programme measured the public, provider, and patient costs of culture-confirmed cholera in four study sites with endemic cholera using a combination of hospital- and community-based studies. Families with culture-proven cases were surveyed at home 7 and 14 days after confirmation of illness. Public costs were measured at local health facilities using a micro-costing methodology. Hospital-based studies found that the costs of severe cholera were USD 32 and 47 in Matlab and Beira. Community-based studies in North Jakarta and Kolkata found that cholera cases cost between USD 28 and USD 206, depending on hospitalization. Patient costs of illness as a percentage of average monthly income were 21% and 65% for hospitalized cases in Kolkata and North Jakarta, respectively. This burden on families is not captured by studies that adopt a provider perspective.
In the incidence patterns of cholera, diphtheria and croup during the past when they were of epidemic proportions, we document a set of cycles (periods), one of which was reported and discussed by A. L. Chizhevsky in the same data with emphasis on the mirroring in human disease of the ~11-year sunspot cycle. The data in this study are based on Chizhevsky’s book The Terrestrial Echo of Solar Storms and on records from the World Health Organization. For meta-analysis, we used the extended linear and nonlinear cosinor. We found a geographically selective assortment of various cycles characterizing the epidemiology of infections, which is the documented novel topic of this paper, complementing the earlier finding in the 21st century or shortly before, of a geographically selective assortment of cycles characterizing human sudden cardiac death. Solar effects, if any, interact with geophysical processes in contributing to this assortment.
Analysis of data; cholera; diphtheria; epidemics; outbreaks
We recently developed and validated an index of socioeconomic status (SES) termed HOUSES (HOUsing-based index of SocioEconomic Status) based on real property data. We assessed whether HOUSES overcomes the absence of SES measures in medical records and is associated with risk of invasive pneumococcal disease (IPD) in children. We conducted a population-based case control study of children in Olmsted County, MN diagnosed with IPD (1996–2005). Each case was age- and gender-matched to two controls. HOUSES was derived using a previously reported algorithm from publicly available housing attributes (the higher HOUSES, the higher SES). HOUSES was available for 92.3% (n=97) and maternal education level for 43% (n=45). HOUSES was inversely associated with risk of IPD (odds ratio: 0.22, 95%CI: 0.05–0.89, p=0.034) whereas maternal education was not (OR: 0.77, 95% CI: 0.50–1.19, p=0.24). HOUSES may be useful for overcoming a paucity of conventional SES measures in commonly used datasets in epidemiological research.
Streptococcus pneumoniae; invasive pneumococcal disease; social class; socioeconomic status; epidemiology; education; immunization; housing; child
There is a strong relationship between socioeconomic status (SES) and health outcomes in the U.S, though the mechanisms are poorly understood. Increasing evidence points to links between lifelong exposure to infectious disease and subsequent chronic disease. Exposure and susceptibility to infections may be one way SES affects long-term health, though little population-based research to date has examined social patterning of infections in the U.S. This paper tests the relationship between income, education, race/ethnicity and seroprevalence of cytomegalovirus (CMV) infection at different ages in a representative sample of the U.S. population, and tests potential mediators for these relationships. The study finds significant racial and socioeconomic disparities in CMV seroprevalence beginning at early ages and persisting into middle age. Potential exposures do not explain the relationship between socioeconomic status and CMV positivity. Because reactivation of latent CMV infections may contribute to chronic disease and immune decline later in life, future research should determine the exposure or susceptibility pathways responsible for these disparities in the prevalence of CMV infection.
Socioeconomic factors; Immunity; Latent Infection; Cytomegalovirus