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Background: In response to the COVID-19 pandemic, a new oral antiviral called nirmatrelvirritonavir (PaxlovidTM) was authorized for use in Canada in January 2022. In vitro studies have reported mutations in Mpro protein that may be associated with the development of nirmatrelvir resistance. Objectives: To survey the prevalence, relevance and temporal patterns of Mpro mutations among SARS-CoV-2 Omicron lineages in Ontario, Canada. Methods: A total of 93,082 Mpro gene sequences from December 2021 to September 2023 were analyzed. Reported in vitro Mpro mutations were screened against our database using in-house data science pipelines to determine the nirmatrelvir resistance. Negative binomial regression was conducted to analyze the temporal trends in Mpro mutation counts over the study time period. Results: A declining trend was observed in non-synonymous mutations of Mpro sequences, showing a 7.9% reduction (95% CI: 6.5%--9.4%; p<0.001) every 30 days. The P132H was the most prevalent mutation (higher than 95%) in all Omicron lineages. In vitro nirmatrelvir-resistant mutations were found in 3.12% (n=29/929) Omicron lineages with very low counts, ranging from one to 19. Only two mutations, A7T (n=19) and M82I (n=9), showed temporal presence among the BA.1.1 in 2022 and the BQ.1.2.3 in 2022, respectively. Conclusion: The observations suggest that, as of September 2023, no significant or widespread resistance to nirmatrelvir has developed among SARS-CoV-2 Omicron variants in Ontario. This study highlights the importance of creating automated monitoring systems to track the emergence of nirmatrelvir-resistant mutations within the SARS-CoV-2 virus, utilizing genomic data generated in real-time. [ABSTRACT FROM AUTHOR]

Nontuberculous mycobacteria (NTM) pulmonary disease (PD) is increasing in North America (1-3). The 2 most common causes of NTM PD in Ontario, Canada, are Mycobacterium avium complex (MAC) and M. [...]

Mycobacterium xenopi is responsible for pulmonary disease (PD) in Europe and Canada. Despite its high prevalence and increasing clinical importance, little is known about the genetic diversity of M. xenopi. Through a prospective study for M. xenopi strain type and the relation to clinical phenotype, 39 patients with M. xenopi PD were analyzed. Our study demonstrated that sequence type (ST) 5 was dominant in Ontario among 15 distinct STs and caused PD in people even without underlying lung disease, whereas disease due to non-ST5 was found almost exclusively in patients with underlying lung disease., Author(s): Takashi Hirama [sup.1] [sup.2] [sup.3] , Alex Marchand-Austin [sup.4] [sup.5] , Jennifer Ma [sup.5] , David C. Alexander [sup.6] , Sarah K. Brode [sup.1] [sup.2] [sup.3] , Theodore K. [...]

Nontuberculous mycobacteria (NTM) cause pulmonary and nonpulmonary disease, but most isolates and disease cases are pulmonary (1). Studies have demonstrated temporal increases in pulmonary NTM isolation and disease (2,3). To [...]

Nontuberculous mycobacterial pulmonary disease (NTM-PD) is an increasingly common problem (1-3) that is associated with substantially impaired quality of life (4) and is difficult and costly to treat (5,6). At [...]

Middle East respiratory syndrome coronavirus (MERS-CoV) was originally described in 2012 in a patient with severe pneumonia in Saudi Arabia (1). The virus has been detected in several countries of [...]

Pulmonary nontuberculous mycobacterial (pNTM) disease is clinically challenging. Therapy entails complex antimycobacterial drug combinations, typically for 18 months (1), often with poor tolerability (2) and limited success (3). pNTM disease [...]

Respiratory tract illnesses are a major cause of illness and death among elderly persons, especially those in long-term care facilities. Although the most commonly identified viruses have been influenza virus [...]

Respiratory infection outbreaks in institutions housing large numbers of residents create an ideal environment for disease transmission (1). Patients in long-term care facilities (LTCFs) for the elderly are more susceptible [...]

Background The role of antibiotics in preventing urinary tract infection (UTI) in older adults is unknown. We sought to quantify the benefits and risks of antibiotic prophylaxis among older adults. Methods We conducted a matched cohort study comparing older adults (≥66 years) receiving antibiotic prophylaxis, defined as antibiotic treatment for ≥30 days starting within 30 days of a positive culture, with patients with positive urine cultures who received antibiotic treatment but did not receive prophylaxis. We matched each prophylaxis recipient to 10 nonrecipients based on organism, number of positive cultures, and propensity score. Outcomes included (1) emergency department (ED) visit or hospitalization for UTI, sepsis, or bloodstream infection within 1 year; (2) acquisition of antibiotic resistance in urinary tract pathogens; and (3) antibiotic-related complications. Results Overall, 4.7% (151/3190) of UTI prophylaxis patients and 3.6% (n = 1092/30 542) of controls required an ED visit or hospitalization for UTI, sepsis, or bloodstream infection (hazard ratio [HR], 1.33; 95% confidence interval [CI], 1.12–1.57). Acquisition of antibiotic resistance to any urinary antibiotic (HR, 1.31; 95% CI, 1.18–1.44) and to the specific prophylaxis agent (HR, 2.01; 95% CI, 1.80–2.24) was higher in patients receiving prophylaxis. While the overall risk of antibiotic-related complications was similar between groups (HR, 1.08; 95% CI,.94–1.22), the risk of Clostridioides difficile and general medication adverse events was higher in prophylaxis recipients (HR [95% CI], 1.56 [1.05–2.23] and 1.62 [1.11–2.29], respectively). Conclusions Among older adults with UTI, the harms of long-term antibiotic prophylaxis may outweigh their benefits. [ABSTRACT FROM AUTHOR]

Background Vaccine effectiveness (VE) studies provide essential evidence on waning vaccine-derived immunity, a major threat to pertussis control. We evaluated how study design affects estimates by comparing 2 case-control studies conducted in Ontario, Canada. Methods We compared results from a test-negative design (TND) with a frequency-matched design (FMD) case-control study using pertussis cases from 2005–2015. In the first study, we identified test-negative controls from the public health laboratory that diagnosed cases and, in the second, randomly selected controls from patients attending the same physicians that reported cases, frequency matched on age and year. We compared characteristics of cases and controls using standardized differences. Results In both designs, VE estimates for the early years postimmunization were consistent with clinical trials (TND, 84%; FMD, 89% at 1–3 years postvaccination) but diverged as time since last vaccination increased (TND, 41%; FMD, 74% by 8 years postvaccination). Overall, we observed lower VE and faster waning in the TND than the FMD. In the TND but not FMD, controls differed from cases in important confounders, being younger, having more comorbidities, and higher healthcare use. Differences between the controls of each design were greater than differences between cases. TND controls were more likely to be unvaccinated or incompletely vaccinated than FMD controls (P  < .001). Conclusions The FMD adjusted better for healthcare-seeking behavior than the TND. Duration of protection from pertussis vaccines is unclear because estimates vary by study design. Caution should be exercised by experts, researchers, and decision makers when evaluating evidence on optimal timing of boosters. [ABSTRACT FROM AUTHOR]

Background: Ontario is 1 of 5 provinces that immunize adolescents for hepatitis B virus (HBV), despite the World Health Organization recommendation for universal birth dose vaccination. One rationale for not vaccinating at birth is that universal prenatal screening and related interventions prevent vertical transmission. The aims of our study were to evaluate the uptake and epidemiology of prenatal HBV screening, and to determine the number of children in Ontario with a diagnosis of HBV before adolescent vaccination.Methods: We extracted data from ICES, Public Health Ontario and Better Outcomes & Registry Network (BORN) Ontario databases. We assessed prenatal screening uptake and prevalence of prenatal hepatitis B surface antigen (HBsAg) from 2012 to 2016, as well as subsequent hepatitis B e-antigen (HBeAg) and HBV DNA testing and percent positivity. We used age and region to subcategorize the results. In a separate unlinked analysis, we evaluated the number of children positive for HBV aged 0-11 years who were born in Ontario from 2003 to 2013.Results: From 2012 to 2016, 93% of pregnant women were screened for HBV, with an HBsAg prevalence of 0.6%. Prevalence of HBsAg increased with age, peaking at older than 45 years at 3%. North Toronto had the highest overall prevalence of 1.5%, whereas northern Ontario had the lowest. Of women who were HBsAg positive, HBeAg and HBV DNA tests were subsequently ordered in 13% and 38%, respectively. Of children born in Ontario between 2003 and 2013, 139 of 23 759 tested positive for HBV.Interpretation: Prenatal HBV screening is not universal and subsequent evaluation is poor, limiting optimal intervention and possibly contributing to some Ontario-born children being given a diagnosis of HBV before age 12 years. These findings underscore the limitations of the province's adolescent vaccination strategy. [ABSTRACT FROM AUTHOR]

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Purpose Population-based cohorts of diagnosed people living with HIV (PLWH) are limited worldwide. In Ontario, linked HIV diagnostic and viral load (VL) test databases are centralised and contain laboratory data commonly used to measure engagement in HIV care. We used these linked databases to create a population-based, retrospective cohort of diagnosed PLWH in Ontario, Canada. Participants A datamart was created by integrating diagnostic and VL databases and linking records at the individual level. These databases contain information on laboratory test results and sociodemographic/clinical information collected on requisition/surveillance forms. Datamart individuals enter our cohort with the first record of a nominal HIV-positive diagnostic test (1985-2015) or VL test (1996-2015), and remain unless administratively lost to follow-up (LTFU; no VL test for >2 years and no VL test in later years). Non-nominal diagnostic tests are excluded as they lack identifying information to permit linkage to other tests. However, individuals diagnosed non-nominally are included in the cohort with record of a VL test. The LTFU rule is applied to indirectly censor for death/out-migration. Findings to date As of the end of 2015, the datamart contained 40 372 HIV-positive diagnostic tests and 23 851 individuals with =1 VL test. Almost half (46.3%) of the diagnostic tests were non-nominal and excluded, although this was lower (~15%) in recent years. Overall, 29 587 individuals have entered the cohort--contributing 229 302 person-years of follow-up since 1996. Between 2000 and 2015, the number of diagnosed PLWH (cohort individuals not LTFU) increased from 8859 to 16 110, and the percent who were aged =45 years increased from 29.1% to 62.6%. The percent of diagnosed PLWH who were virally suppressed (<200 copies/mL) increased from 40.7% in 2000 to 79.5% in 2015. Future plans We plan to conduct further analyses of HIV care engagement and link to administrative databases with information on death, migration, physician billing claims and prescriptions. Linkage to other data sources will address cohort limitations and expand research opportunities. [ABSTRACT FROM AUTHOR]

Objectives: Compare the molecular epidemiology of tuberculosis (TB) between two large Canadian provinces–Ontario and British Columbia (BC)–to identify genotypic clusters within and across both provinces, allowing for an improved understanding of genotype data and providing context to more accurately identify clusters representing local transmission. Design: We compared 24-locus Mycobacterial Interspersed Repetitive Units-Variable Number of Tandem Repeats (MIRU-VNTR) genotyping for 3,314 Ontario and 1,602 BC clinical Mycobacterium tuberculosis isolates collected from 2008 through 2014. Laboratory data for each isolate was linked to case-level records to obtain clinical and demographic data. Results: The demographic characteristics of persons with TB varied between provinces, most notably in the proportion of persons born outside Canada, which was reflected in the large number of unique genotypes (n = 3,461). The proportion of clustered isolates was significantly higher in BC. Substantial clustering amongst non-Lineage 4 TB strains was observed within and across the provinces. Only two large clusters (≥10 cases/cluster) representing within province transmission had interprovincial genotype matches. Conclusion: We recommend expanding analysis of shared genotypes to include neighbouring jurisdictions, and implementing whole genome sequencing to improve identification of TB transmission, recognize outbreaks, and monitor changing trends in TB epidemiology. [ABSTRACT FROM AUTHOR]

Background: The HIV cascade is an important framework for assessing systems of care, but population-based assessment is lacking for most jurisdictions worldwide. We measured cascade indicators over time in a population-based cohort of diagnosed people living with HIV (PLWH) in Ontario, Canada. Methods: We created a retrospective cohort of diagnosed PLWH using a centralized laboratory database with HIV diagnostic and viral load (VL) test records linked at the individual-level. Individuals enter the cohort with record of a nominal HIV-positive diagnostic test or VL test, and remain unless administratively lost to follow-up (LTFU, >2 consecutive years with no VL test and no VL test in later years). We calculated the annual percent of diagnosed PLWH (cohort individuals not LTFU) between 2000 and 2015 who were in care (≥1 VL test), on ART (as documented on VL test requisition) or virally suppressed (<200 copies/ml). We also calculated time from diagnosis to linkage to care and viral suppression among individuals newly diagnosed with HIV. Analyses were stratified by sex and age. Upper/lower bounds were calculated using alternative indicator definitions. Results: The number of diagnosed PLWH increased from 8,859 (8,859–11,389) in 2000 to 16,110 (16,110–17,423) in 2015. Over this 16-year period, the percent of diagnosed PLWH who were: in care increased from 81% (63–81%) to 87% (81–87%), on ART increased from 55% (34–60%) to 81% (70–82%) and virally suppressed increased from 41% (23–46%) to 80% (67–81%). Between 2000 and 2014, the percent of newly diagnosed individuals who linked to care within three months of diagnosis or achieved viral suppression within six months of diagnosis increased from 67% to 82% and from 22% to 42%, respectively. Estimates were generally lower for females and younger individuals. Discussion: HIV cascade indicators among diagnosed PLWH in Ontario improved between 2000 and 2015, but gaps still remain—particularly for younger individuals. [ABSTRACT FROM AUTHOR]

Introduction: Under-reporting of pertussis cases is a longstanding challenge. We estimated the true number of pertussis cases in Ontario using multiple data sources, and evaluated the completeness of each source. Methods: We linked data from multiple sources for the period 2009 to 2015: public health reportable disease surveillance data, public health laboratory data, and health administrative data (hospitalizations, emergency department visits, and physician office visits). To estimate the total number of pertussis cases in Ontario, we used a three-source capture-recapture analysis stratified by age (infants, or aged one year and older) and adjusting for dependency between sources. We used the Bayesian Information Criterion to compare models. Results: Using probable and confirmed reported cases, laboratory data, and combined hospitalizations/emergency department visits, the estimated total number of cases during the six-year period amongst infants was 924, compared with 545 unique observed cases from all sources. Using the same sources, the estimated total for those aged 1 year and older was 12,883, compared with 3,304 observed cases from all sources. Only 37% of infants and 11% for those aged 1 year and over admitted to hospital or seen in an emergency department for pertussis were reported to public health. Public health reporting sensitivity varied from 2% to 68% depending on age group and the combination of data sources included. Sensitivity of combined hospitalizations and emergency department visits varied from 37% to 49% and of laboratory data from 1% to 50%. Conclusions: All data sources contribute cases and are complementary, suggesting that the incidence of pertussis is substantially higher than suggested by routine reports. The sensitivity of different data sources varies. Better case identification is required to improve pertussis control in Ontario. [ABSTRACT FROM AUTHOR]

Mycobacterium xenopi is responsible for pulmonary disease (PD) in Europe and Canada. Despite its high prevalence and increasing clinical importance, little is known about the genetic diversity of M. xenopi. Through a prospective study for M. xenopi strain type and the relation to clinical phenotype, 39 patients with M. xenopi PD were analyzed. Our study demonstrated that sequence type (ST) 5 was dominant in Ontario among 15 distinct STs and caused PD in people even without underlying lung disease, whereas disease due to non-ST5 was found almost exclusively in patients with underlying lung disease. [ABSTRACT FROM AUTHOR]

Objective: Develop a tool to disseminate integrated laboratory, clinical, and demographic case data necessary for improved contact tracing and outbreak detection of tuberculosis (TB).Methods: In 2007, the Public Health Ontario Laboratories implemented a universal genotyping program to monitor the spread of TB strains within Ontario. Ontario Universal Typing of TB (OUT-TB) Web utilizes geographic information system (GIS) technology with a relational database platform, allowing TB control staff to visualize genotyping matches and microbiological data within the context of relevant epidemiological and demographic data.Results: OUT-TB Web is currently available to the 8 health units responsible for >85% of Ontario's TB cases and is a valuable tool for TB case investigation. Users identified key features to implement for application enhancements, including an e-mail alert function, customizable heat maps for visualizing TB and drug-resistant cases, socioeconomic map layers, a dashboard providing TB surveillance metrics, and a feature for animating the geographic spread of strains over time.Conclusion: OUT-TB Web has proven to be an award-winning application and a useful tool. Developed and enhanced using regular user feedback, future versions will include additional data sources, enhanced map and line-list filter capabilities, and development of a mobile app. [ABSTRACT FROM AUTHOR]

Background: A resurgence of pertussis cases among both vaccinated and unvaccinated people raises questions about vaccine effectiveness over time. Our objective was to study the effectiveness of the pertussis vaccine and characterize the effect of waning immunity and whole-cell vaccine priming.Methods: We used the test-negative design, a nested case-control study with test-negative individuals as controls. We constructed multivariable logistic regression models to estimate odds ratios (ORs). Vaccine effectiveness was calculated as (1 - OR) × 100. We assessed waning immunity by calculating the odds of developing pertussis per year since last vaccination and evaluated the relative effectiveness of priming with acellular versus whole-cell vaccine.Results: Between Dec. 7, 2009, and Mar. 31, 2013, data on 5867 individuals (486 test-positive cases and 5381 test-negative controls) were available for analysis. Adjusted vaccine effectiveness was 80% (95% confidence interval [CI] 71% to 86%) at 15-364 days, 84% (95% CI 77% to 89%) at 1-3 years, 62% (95% CI 42% to 75%) at 4-7 years and 41% (95% CI 0% to 66%) at 8 or more years since last vaccination. We observed waning immunity with the acellular vaccine, with an adjusted OR for pertussis infection of 1.27 (95% CI 1.20 to 1.34) per year since last vaccination. Acellular, versus whole-cell, vaccine priming was associated with an increased odds of pertussis (adjusted OR 2.15, 95% CI 1.30 to 3.57).Interpretation: We observed high early effectiveness of the pertussis vaccine that rapidly declined as time since last vaccination surpassed 4 years, particularly with acellular vaccine priming. Considering whole-cell vaccine priming and/or boosters in pregnancy to optimize pertussis control may be prudent. [ABSTRACT FROM AUTHOR]

In August 2014, children’s hospitals in Kansas City, Missouri and Chicago, Illinois notified the Centers for Disease Control and Prevention (CDC) about increased numbers of pediatric patients hospitalized with severe respiratory illness (SRI). In response to CDC reports, Public Health Ontario Laboratories (PHOL) launched an investigation of patients being tested for enterovirus D-68 (EV-D68) in Ontario, Canada. The purpose of this investigation was to enhance our understanding of EV-D68 epidemiology and clinical features. Data for this study included specimens submitted for EV-D68 testing at PHOL from September 1, 2014 to October 31, 2014. Comparisons were made between patients who tested positive for the virus (cases) and those testing negative (controls). EV-D68 was identified in 153/907 (16.8%) of patients tested. In the logistic regression model adjusting for age, sex, setting and time to specimen collection, individuals younger than 20 years of age were more likely to be diagnosed with EV-D68 compared to those 20 and over, with peak positivity at ages 5–9 years. Cases were not more likely to be hospitalized than controls. Cases were more likely to be identified in September than October (OR 8.07; 95% CI 5.15 to 12.64). Routine viral culture and multiplex PCR were inadequate methods to identify EV-D68 due to poor sensitivity and inability to differentiate EV-D68 from other enterovirus serotypes or rhinovirus. Testing for EV-D68 in Ontario from July to December, 2014 detected the presence of EV-D68 virus among young children during September-October, 2014, with most cases detected in September. There was no difference in hospitalization status between cases and controls. In order to better understand the epidemiology of this virus, surveillance for EV-D68 should include testing of symptomatic individuals from all treatment settings and patient age groups, with collection and analysis of comprehensive clinical and epidemiological data. [ABSTRACT FROM AUTHOR]

Bordetella pertussis testing performed using real-time polymerase chain reaction (RT-PCR) is interpreted based on a cycle threshold (Ct) value. At Public Health Ontario Laboratories (PHOL), a Ct value <36 is reported as positive, and Ct values ≥36 and <40 are reported as indeterminate. PHOL reported indeterminate results to physicians and public health units until May 2012, after which these results were only reported to physicians. We investigated the association between Ct value and disease symptom and severity to examine the significance of indeterminate results clinically, epidemiologically and for public health reporting. B. pertussis positive and indeterminate RT-PCR results were linked to pertussis cases reported in the provincial Integrated Public Health Information System (iPHIS), using deterministic linkage. Patients with positive RT-PCR results had a lower median age of 10.8 years compared to 12.0 years for patients with indeterminate results (p = 0.24). Hospitalized patients had significantly lower Ct values than non-hospitalized patients (median Ct values of 20.7 vs. 31.6, p<0.001). The proportion of patients reporting the most indicative symptoms of pertussis did not differ between patients with positive vs. indeterminate RT-PCR results. Taking the most indicative symptoms of pertussis as the gold-standard, the positive predictive value of the RT-PCR test was 68.1%. RT-PCR test results should be interpreted in the context of the clinical symptoms, age, vaccination status, prevalence, and other factors. Further information on interpretation of indeterminate RT-PCR results may be needed, and the utility of reporting to public health practitioners should be re-evaluated. [ABSTRACT FROM AUTHOR]

Abstract: An immuno-informatics study was conducted to determine possible pre-existing T cellular immunity to the recently emerged swine-origin triple reassortant H3N2 variant (S-OtrH3N2v-2011) which acquired the matrix gene of influenza A (H1N1)pdm09. Given the genetic origin of S-OtrH3N2v-2011, our study focused on the hemagglutinin (HA) and matrix1 (M1) proteins to identify common and conserved T cell epitopes. We compared HA CD4+ T cell epitopes of S-OtrH3N2v-2011 with seasonal H3N2 (1968–2011)-HA proteins. M1 CD4+ and CD8+ T cell epitopes of S-OtrH3N2v-2011 were compared with the M1 proteins of seasonal H1N1 (1977–2009) and A (H1N1)pdm09 (2009–2011) subtypes. The results revealed a high conservancy of epitopes localized particularly on HA2 and the entire M1 protein. The overall cross reactivity of predicted CD4+ T cell epitopes with previously experimentally defined (Immuno Epitope Database) CD4+ T epitopes of HA and M1 proteins was ∼51%. CD8+ T cell cross-reactivity of ∼74% was documented for M1 protein. Analysis suggests possible pre-existing CD4+ T cell immunity to S-OtrH3N2v-2011 in the human population. [Copyright &y& Elsevier]

Highlights • Immunization provides highly effective protection from pertussis. • Children are most protected from pertussis in the first few years after immunization. • Protection is sustained for the first decade after the last dose of vaccine, but subsequently falls rapidly. • Method of control selection affects estimates of vaccine effectiveness. Abstract Background Resurgences of pertussis have occurred in several high-income countries, often linked to waning of immunity from acellular pertussis vaccines. The degree of waning observed has varied by study design and setting. In Ontario, pertussis has not shown a substantial resurgence in the past decade. The routine immunization schedule comprises three priming doses in infancy, toddler and pre-school doses, and an adolescent dose at 14–16 years of age. Methods We estimated pertussis vaccine effectiveness (VE) through a case-control study of 1335 cases statutorily reported to public health in Ontario and occurring between January 1, 2009 and March 31, 2015, compared with 5340 randomly selected population controls, frequency-matched by age, primary-care provider and year of diagnosis. Pertussis cases met provincial confirmed or probable case definitions. We used multivariable logistic regression to estimate crude and adjusted odds ratios (aOR). Results VE against pertussis was sustained between 92% (95% confidence interval (95%CI) 88–95%) in 2–3 year olds and 90% (95%CI: 80–95%) in 8–9 year olds, but fell rapidly to 49% (95%CI: 2–73%) in children 12–13 years of age. VE following the teenage booster given at 14–16 years in Ontario reached 76% (95%CI: 52–88%) in 14–16 year olds and 78% (95%CI: −31 to 96%) in those 16–22 years old. For children who were up-to-date with the immunization schedule, VE declined from 87% (95%CI: 84–90%) during the first year to 74% (95%CI: 63–82%) after 8 or more years following their last dose of immunization. Conclusions VE is high during the first decade of life but then falls rapidly. Protection is not fully restored by the teenage booster. Our findings are consistent with the localized outbreaks we observe in high school children and underline the importance of additional policies to protect infants. [ABSTRACT FROM AUTHOR]

Background In 2010, there was an increase in enterovirus meningitis in the province of Ontario, Canada. Concurrently, there was also an increase in coxsackievirus A9-positive specimens in Alberta, Canada. This study aimed to describe the results of an investigation into the increase in coxsackievirus (A9 serotype) in 2010 in Ontario. Methods For the purpose of this study, we report on specimens tested by viral culture at Public Health Ontario Laboratory as part of routine laboratory testing from January 1, 2005 to December 31, 2011. Results Coxsackieviruses represented more than one third of enteroviruses detected, with A9 being the serotype most commonly identified. The most common specimen source in which A9 was isolated was cerebrospinal fluid, followed by nasopharyngeal swabs and stool. Patients in whom A9 was detected were older than individuals with any other coxsackievirus serotype. Conclusions The increase in enterovirus meningitis in Ontario in 2010 was likely due to an increase in A9 circulation. A9 was most commonly identified among children; however A9 may cause severe illness in both children and adults. Monitoring the circulation and epidemiology of enteroviruses can inform clinicians about circulating pathogens to optimize clinical testing and antibiotic use. [ABSTRACT FROM AUTHOR]