Rachel Savage

Older Age and a Reduced Likelihood of 2009 H1N1 Virus Infection

Among persons who were at risk for infection with 2009 H1N1 virus, being born before 1957 was associated with a lower infection risk.

Assessing secondary attack rates among household contacts at the beginning of the influenza A (H1N1) pandemic in Ontario, Canada, April-June 2009: A prospective, observational study

BackgroundUnderstanding transmission dynamics of the pandemic influenza A (H1N1) virus in various exposure settings and determining whether transmissibility differed from seasonal influenza viruses was a priority for decision making on mitigation strategies at the beginning of the pandemic. The objective of this study was to estimate household secondary attack rates for pandemic influenza in a susceptible population where control measures had yet to be implemented.MethodsAll Ontario local health units were invited to participate; seven health units volunteered. For all laboratory-confirmed cases reported between April 24 and June 18, 2009, participating health units performed contact tracing to detect secondary cases among household contacts. In total, 87 cases and 266 household contacts were included in this study. Secondary cases were defined as any household member with new onset of acute respiratory illness (fever or two or more respiratory symptoms) or influenza-like illness (fever plus one additional respiratory symptom). Attack rates were estimated using both case definitions.ResultsSecondary attack rates were estimated at 10.3% (95% CI 6.8-14.7) for secondary cases with influenza-like illness and 20.2% (95% CI 15.4-25.6) for secondary cases with acute respiratory illness. For both case definitions, attack rates were significantly higher in children under 16 years than adults (25.4% and 42.4% compared to 7.6% and 17.2%). The median time between symptom onset in the primary case and the secondary case was estimated at 3.0 days.ConclusionsSecondary attack rates for pandemic influenza A (H1N1) were comparable to seasonal influenza estimates suggesting similarities in transmission. High secondary attack rates in children provide additional support for increased susceptibility to infection.

The epidemiology of travel-related Salmonella Enteritidis in Ontario, Canada, 2010–2011

BackgroundIncreases in the number of salmonellosis cases due to Salmonella Enteritidis (SE) in 2010 and 2011 prompted a public health investigation in Ontario, Canada. In this report, we describe the current epidemiology of travel-related (TR) SE, compare demographics, symptoms and phage types (PTs) of TR and domestically-acquired (DA) cases, and estimate the odds of acquiring SE by region of the world visited.MethodsAll incident cases of culture confirmed SE in Ontario obtained from isolates and specimens submitted to public health laboratories were included in this study. Demographic and illness characteristics of TR and DA cases were compared. A national travel survey was used to provide estimates for the number of travellers to various destinations to approximate rates of SE in travellers. Multivariate logistic regression was used to estimate the odds of acquiring SE when travelling to various world regions.ResultsOverall, 51.9% of SE cases were TR during the study period. This ranged from 35.7% TR cases in the summer travel period to 65.1% TR cases in the winter travel period. Compared to DA cases, TR cases were older and were less likely to seek hospital care. For Ontario travellers, the adjusted odds of acquiring SE was the highest for the Caribbean (OR 37.29, 95% CI 17.87-77.82) when compared to Europe. Certain PTs were more commonly associated with travel (e.g., 1, 4, 5b, 7a, Atypical) than with domestic infection. Of the TR cases, 88.9% were associated with travel to the Caribbean and Mexico region, of whom 90.1% reported staying on a resort. Within this region, there were distinct associations between PTs and countries.ConclusionsThere is a large burden of TR illness from SE in Ontario. Accurate classification of cases by travel history is important to better understand the source of infections. The findings emphasize the need to make travellers, especially to the Caribbean, and health professionals who provide advice to travellers, aware of this risk. The findings may be generalized to other jurisdictions with travel behaviours in their residents similar to Ontario residents.

Risk factors for sporadic domestically acquired Salmonella serovar Enteritidis infections: a case-control study in Ontario, Canada, 2011

In Ontario, Canada, the number of Salmonella Enteritidis (SE) cases increased over the years 2005-2010. A population-based case-control study was undertaken from January to August 2011 for the purpose of identifying risk factors for acquiring illness due to SE within Ontario. A total of 199 cases and 241 controls were enrolled. After adjustment for confounders, consuming any poultry meat [adjusted odds ratio (aOR) 2·24, 95% confidence interval (CI) 1·31-3·83], processed chicken (aOR 3·32, 95% CI 1·26-8·76) and not washing hands following handling of raw eggs (OR 2·82, 95% CI 1·48-5·37) were significantly associated with SE infection. The population attributable fraction was 46% for any poultry meat consumption and 10% for processed chicken. Poultry meat continues to be identified as a risk factor for SE illness. Control of SE at source, as well as proper food handling practices, are required to reduce the number of SE cases.

The use of syndromic surveillance for decision-making during the H1N1 pandemic: A qualitative study

BackgroundAlthough an increasing number of studies are documenting uses of syndromic surveillance by front line public health, few detail the value added from linking syndromic data to public health decision-making. This study seeks to understand how syndromic data informed specific public health actions during the 2009 H1N1 pandemic.MethodsSemi-structured telephone interviews were conducted with participants from Ontario’s public health departments, the provincial ministry of health and federal public health agency to gather information about syndromic surveillance systems used and the role of syndromic data in informing specific public health actions taken during the pandemic. Responses were compared with how the same decisions were made by non-syndromic surveillance users.ResultsFindings from 56 interviews (82% response) show that syndromic data were most used for monitoring virus activity, measuring impact on the health care system and informing the opening of influenza assessment centres in several jurisdictions, and supporting communications and messaging, rather than its intended purpose of early outbreak detection. Syndromic data had limited impact on decisions that involved the operation of immunization clinics, school closures, sending information letters home with school children or providing recommendations to health care providers. Both syndromic surveillance users and non-users reported that guidance from the provincial ministry of health, communications with stakeholders and vaccine availability were driving factors in these public health decisions.ConclusionsSyndromic surveillance had limited use in decision-making during the 2009 H1N1 pandemic in Ontario. This study provides insights into the reasons why this occurred. Despite this, syndromic data were valued for providing situational awareness and confidence to support public communications and recommendations. Developing an understanding of how syndromic data are utilized during public health events provides valuable evidence to support future investments in public health surveillance.

The Effect of Inadequate Initial Empiric Antimicrobial Treatment on Mortality in Critically Ill Patients with Bloodstream Infections: A Multi-Centre Retrospective Cohort Study

Hospital mortality rates are elevated in critically ill patients with bloodstream infections. Given that mortality may be even higher if appropriate treatment is delayed, we sought to determine the effect of inadequate initial empiric treatment on mortality in these patients. A retrospective cohort study was conducted across 13 intensive care units in Canada. We defined inadequate initial empiric treatment as not receiving at least one dose of an antimicrobial to which the causative pathogen(s) was susceptible within one day of initial blood culture. We evaluated the association between inadequate initial treatment and hospital mortality using a random effects multivariable logistic regression model. Among 1,190 patients (1,097 had bacteremia and 93 had candidemia), 476 (40%) died and 266 (22%) received inadequate initial treatment. Candidemic patients more often had inadequate initial empiric therapy (64.5% versus 18.8%), as well as longer delays to final culture results (4 vs 3 days) and appropriate therapy (2 vs 0 days). After adjustment, there was no detectable association between inadequate initial treatment and mortality among bacteremic patients (Odds Ratio (OR): 1.02, 95% Confidence Interval (CI) 0.70–1.48); however, candidemic patients receiving inadequate treatment had nearly three times the odds of death (OR: 2.89, 95% CI: 1.05–7.99). Inadequate initial empiric antimicrobial treatment was not associated with increased mortality in bacteremic patients, but was an important risk factor in the subgroup of candidemic patients. Further research is warranted to improve early diagnostic and risk prediction methods in candidemic patients.

Evaluating risk factors for endemic human Salmonella Enteritidis infections with different phage types in Ontario, Canada using multinomial logistic regression and a case-case study approach

BackgroundIdentifying risk factors for Salmonella Enteritidis (SE) infections in Ontario will assist public health authorities to design effective control and prevention programs to reduce the burden of SE infections. Our research objective was to identify risk factors for acquiring SE infections with various phage types (PT) in Ontario, Canada. We hypothesized that certain PTs (e.g., PT8 and PT13a) have specific risk factors for infection.MethodsOur study included endemic SE cases with various PTs whose isolates were submitted to the Public Health Laboratory-Toronto from January 20th to August 12th, 2011. Cases were interviewed using a standardized questionnaire that included questions pertaining to demographics, travel history, clinical symptoms, contact with animals, and food exposures. A multinomial logistic regression method using the Generalized Linear Latent and Mixed Model procedure and a case-case study design were used to identify risk factors for acquiring SE infections with various PTs in Ontario, Canada. In the multinomial logistic regression model, the outcome variable had three categories representing human infections caused by SE PT8, PT13a, and all other SE PTs (i.e., non-PT8/non-PT13a) as a referent category to which the other two categories were compared.ResultsIn the multivariable model, SE PT8 was positively associated with contact with dogs (OR=2.17, 95% CI 1.01-4.68) and negatively associated with pepper consumption (OR=0.35, 95% CI 0.13-0.94), after adjusting for age categories and gender, and using exposure periods and health regions as random effects to account for clustering.ConclusionsOur study findings offer interesting hypotheses about the role of phage type-specific risk factors. Multinomial logistic regression analysis and the case-case study approach are novel methodologies to evaluate associations among SE infections with different PTs and various risk factors.

Strengths and limitations of assessing influenza vaccine effectiveness using routinely collected, passive surveillance data in Ontario, Canada, 2007 to 2012: balancing efficiency versus quality.

Prompt evaluation of annual influenza vaccine effectiveness (IVE) is important. IVE is estimated in Ontario using a test-negative design (TND) within a national sentinel surveillance network (SPSN). To explore alternative approaches, we applied the screening method (SM) during five seasons spanning 2007 to 2012 to passive surveillance data to determine whether routinely collected data could provide unbiased IVE estimates. Age-adjusted SM-IVE estimates, excluding 2008/09 pandemic cases and cases with missing immunisation status, were compared with TND-IVE estimates in SPSN participants, adjusted for age, comorbidity, week of illness onset and interval to specimen collection. In four seasons, including the 2009 pandemic, the SM underestimated IVE (22–39% seasonal; 72% pandemic) by 20 to 35% relative to the TND-IVE (58–63% seasonal; 93% pandemic), except for the 2010/11 season when both estimates were low (33% and 30%, respectively). Half of the cases in the routine surveillance data lacked immunisation information; imputing all to be unimmunised better aligned SM-IVE with TND-IVE, instead overestimating in four seasons by 4 to 29%. While the SM approach applied to routine data may offer the advantage of timeliness, ease and efficiency, methodological issues related to completeness of vaccine information and/or case ascertainment may constitute trade-offs in reliability.

Assessing the Relative Timeliness of Ontario's Syndromic Surveillance Systems for Early Detection of the 2009 Influenza H1N1 Pandemic Waves

OBJECTIVES: Building on previous research noting variations in the operation and perceived utility of syndromic surveillance systems in Ontario, the timeliness of these different syndromic systems for detecting the onset of both 2009 H1N1 pandemic (A(H1N1)pdm09) waves relative to laboratory testing data was assessed using a standardized analytic algorithm.METHODS: Syndromic data, specifically local emergency department (ED) visit and school absenteeism data, as well as provincial Telehealth (telephone helpline) and antiviral prescription data, were analyzed retrospectively for the period April 1, 2009 to January 31, 2010. The C2-MEDIUM aberration detection method from the US Centers for Disease Control and Prevention’s EARS software was used to detect increases above expected in syndromic data, and compared to laboratory alerts, defined as notice of confirmed A(H1N1)pdm09 cases over two consecutive days, to assess relative timeliness.RESULTS: In Wave 1, provincial-level alerts were detected for antiviral prescriptions and Telehealth respiratory calls before the laboratory alert. In Wave 2, Telehealth respiratory calls similarly alerted in advance of the laboratory, while local alerts from ED visit, antiviral prescription and school absenteeism data varied in timing relative to the laboratory alerts. Alerts from syndromic data were also observed to coincide with external factors such as media releases.CONCLUSIONS: Alerts from syndromic surveillance systems may be influenced by external factors and variation in system operations. Further understanding of both the impact of external factors on surveillance data and standardizing protocols for defining alerts is needed before the use of syndromic surveillance systems can be optimized.RésuméOBJECTIFS: À partir des résultats de recherches antérieures sur les écarts dans le fonctionnement et l’utilité perçue des systèmes de surveillance syndromique en Ontario, nous avons évalué, à l’aide d’un algorithme analytique standardisé, la rapidité avec laquelle les différents systèmes syndromiques ont détecté l’apparition des deux vagues de la pandémie de grippe H1N1 de 2009 (A(H1N1)pdm09) par rapport aux données des épreuves de laboratoire.MÉTHODE: Les données syndromiques, plus précisément les visites aux services d’urgence locaux et l’absentéisme dans les écoles, ainsi que les appels à Télésanté (une ligne d’assistance téléphonique provinciale) et les ordonnances d’antiviraux, ont été analysées rétrospectivement pour la période du 1er avril 2009 au 31 janvier 2010. Nous avons utilisé la méthode de détection des aberrations C2-MEDIUM du logiciel EARS des Centers for Disease Control and Prevention des États-Unis pour déceler les hausses supérieures aux prévisions dans les données syndromiques, et nous les avons comparées aux alertes des laboratoires, définies comme étant les avis de cas de grippe A(H1N1)pdm09 confirmés au cours de deux journées consécutives, pour évaluer la rapidité relative des systèmes de surveillance syndromique.RÉSULTATS: Durant la 1e vague, des alertes de niveau provincial ont été détectées, dans les ordonnances d’antiviraux et les appels pour problèmes respiratoires à Télésanté, avant les alertes des laboratoires. Durant la 2e vague, les appels pour problèmes respiratoires à Télésanté ont aussi précédé les alertes des laboratoires, mais les alertes locales liées aux visites aux urgences, aux ordonnances d’antiviraux et aux taux d’absentéisme dans les écoles ont varié dans le temps par rapport aux alertes des laboratoires. Il a aussi été observé que les alertes déclenchées par les données syndromiques coïncidaient avec des facteurs externes, comme les communiqués.CONCLUSIONS: Les alertes des systèmes de surveillance syndromique peuvent être influencées par des facteurs externes et des variations dans le fonctionnement des systèmes. Il faudrait pousser la recherche sur deux plans: l’impact exercé par les facteurs externes sur les données de surveillance et la normalisation des protocoles de déclenchement des alertes, avant de pouvoir optimiser l’utilisation des systèmes de surveillance syndromique.

How Can We Keep Immigrant Travelers Healthy? Health Challenges Experienced by Canadian South Asian Travelers Visiting Friends and Relatives:

Immigrant travelers who visit friends and relatives (VFR travelers) experience substantially higher rates of travel-related infections than other travelers, in part due to low uptake of pretravel health advice. While barriers to accessing advice have been identified, better characterization is needed to inform targeted interventions. We sought to understand how South Asian VFR travelers perceived and responded to travel-related health risks by conducting group interviews with 32 adult travelers from an ethnoculturally diverse Canadian region. Travelers positioned themselves as knowledgeable of key health risks, despite not seeking pretravel health advice. Their responses to risks were pragmatic and rooted in experience, but often constrained by competing concerns, including rushed travel, familial obligations, cost, and a desire to preserve authentic experiences. Moving beyond risk awareness to reinforcing the value of medical advice and intervention, in a manner that is sensitive to these unique concerns, is needed when delivering tailored health promotion messages to VFR travelers.