Breakthrough cases of mpox: One-dose vaccination is associated with milder clinical manifestations.

BACKGROUND: Very few studies have investigated the effectiveness of vaccination in decreasing the severity of breakthrough mpox. Our goal was to estimate the strength of the associations between recent mpox vaccination with MVA-BN and various clinical manifestations of the disease. METHODS: Telephone interviews using standardized questionnaires, upon notification and 28 days later, of the 403 persons with mpox reported to Montreal Public Health in 2022. MVA-BN vaccination data were obtained from the provincial immunization registry. The main outcomes were numbers of skin lesions and body sites affected, other clinical manifestations (OCM) compatible with mpox, complications, and hospitalization. FINDINGS: 155 persons with mpox (39% of 403) had received 1 dose of vaccine at least 14 days before symptom onset. One-dose vaccination, adjusting for age and HIV status, was significantly associated with fewer lesions, sites affected with lesions, and OCMs. HIV-positive persons with breakthrough mpox reported significantly more lesions, sites affected, and OCMs at initial interview, than HIV-negative ones. However, vaccination was associated with a lower risk of all outcomes to the same degree irrespective of HIV status. INTERPRETATION: One dose of MVA-BN vaccine was about 60% effective in decreasing the frequency and extent of clinical manifestations, among both HIV-positive and HIV-negative persons with breakthrough mpox. Beyond preventing infection, mpox vaccination can be promoted to reduce clinical manifestations in persons at risk for mpox, even if HIV+ . FUNDING: This work used data obtained as part of Montreal Public Health's 2022 mpox outbreak response and received no external funding.

Analysis of COVID-19 Risk Following a Ring Vaccination Intervention to Address SARS-CoV-2 Alpha Variant Transmission in Montreal, Canada.

Importance: Given limited COVID-19 vaccine availability early in the pandemic, optimizing immunization strategies was of paramount importance. Ring vaccination has been used successfully to control transmission of other airborne respiratory viruses. Objective: To assess the association of a ring vaccination intervention on COVID-19 spread in the initial epicenter of SARS-CoV-2 Alpha variant transmission in Montreal, Canada. Design, Setting, and Participants: This cohort study compared COVID-19 daily disease risk in 3 population-based groups of neighborhoods in Montreal, Canada, defined by their intervention-specific vaccine coverage at the neighborhood level: the primary intervention group (500 or more vaccinated persons per 10 000 persons), secondary intervention group (95 to 499), and control group (0 to 50). The groups were compared within each of 3 time periods: before intervention (December 1, 2020, to March 16, 2021), during and immediately after intervention (March 17 to April 17, 2021), and 3 weeks after the intervention midpoint (April 18 to July 18, 2021). Data were analyzed between June 2021 and November 2021. Exposures: Vaccination targeted parents and teachers of children attending the 32 schools and 48 childcare centers in 2 adjacent neighborhoods with highest local transmission (case counts) of Alpha variant shortly after its introduction. Participants were invited to receive 1 dose of mRNA vaccine between March 22 and April 9, 2021 (before vaccine was available to these age groups). Main Outcomes and Measures: COVID-19 risk in 3 groups of neighborhoods based on intervention-specific vaccine coverage. Results: A total of 11 794 residents were immunized, with a mean (SD) age of 43 (8) years (range, 16-93 years); 5766 participants (48.9%) lived in a targeted neighborhood, and 9784 (83.0%) were parents. COVID-19 risk in the primary intervention group was significantly higher than in the control group before (unadjusted risk ratio [RR], 1.58; 95% CI 1.52-1.65) and during (RR, 1.63; 95% CI, 1.52-1.76) intervention, and reached a level similar to the other groups in the weeks following the intervention (RR, 1.03; 95% CI, 0.94-1.12). A similar trend was observed when restricting to SARS-CoV-2 variants and persons aged 30 to 59 years (before: RR, 1.72; 95% CI, 1.63-1.83 vs after: RR, 1.01; 95% CI, 0.88-1.17). Conclusions and Relevance: Our findings show that ring vaccination was associated with a reduction in COVID-19 risk in areas with high local transmission of Alpha variant shortly after its introduction. Ring vaccination may be considered as an adjunct to mass immunization to control transmission in specific areas, based on local epidemiology.

Compliance with COVID-19 preventive measures is high among university-level students in Québec, Canada.

Background: Canada's nationwide lockdown to curb coronavirus disease 2019 (COVID-19) infections affected many sectors of activity, including universities. During the 2020-2021 academic year, all students were forced to follow their lectures from home and the only in-person activity permitted to Québec university level students was to study in designated spaces of campus libraries where COVID-19 preventive measures were in place and mandatory at all times for all staff and students. The objective of this study is to evaluate university-level students' compliance with COVID-19 preventive measures in a Québec campus library. Methods: A direct in-person evaluation by a trained observer was put in place to assess students' compliance with COVID-19 preventive measures defined as proper mask wearing and 2 meter distancing. Measurements were made each Wednesday, Saturday, and Sunday at 10 a.m., 2 p.m., and 6 p.m. from March 28 to April 25, 2021, in a university library in Québec, Canada. Results: Students' compliance with COVID-19 preventive measures was high overall (78.4%) and increased over the weeks, with differences between weeks, weekdays, and time of day. Non-compliance was lower on weeks three and four of the assessment compared with week one, and higher on Sunday compared with Wednesday. Differences seen throughout the day were not statistically significant. Non-compliance with physical distancing was rarely seen. Conclusion: Most university-level students are compliant with COVID-19 preventive measures in a Québec university library: an encouraging behaviour from a public health perspective. These findings may support public health authorities or university administrators in decisions regarding different COVID-19 preventive measures directed to different universities settings, as this method can be applied to focused, rapid observational studies and can lead to data of sufficient statistical power.

A population-based study of chronic hepatitis C in immigrants and non-immigrants in Quebec, Canada.

BACKGROUND: Immigrants originating from intermediate and high HCV prevalence countries may be at increased risk of exposure to hepatitis C infection (HCV) in their countries of origin, however they are not routinely screened after arrival in most low HCV prevalence host countries. We aimed to describe the epidemiology of HCV in immigrants compared to the Canadian born population. METHODS: Using the reportable infectious disease database linked to the landed immigration database and several provincial administrative databases, we assembled a cohort of all reported cases of HCV in Quebec, Canada (1998-2008). Underlying co-morbidities were identified in the health services databases. Stratum specific rates of reported cases/100,000, rate ratios (RRs) and trends over the study period were estimated. RESULTS: A total of 20,862 patients with HCV were identified, among whom 1922 (9.2%) were immigrants. Immigrants were older and diagnosed a mean of 9.8 ± 7 years after arrival. The Canadian born population was more likely to have behavior co-morbidities (problematic alcohol or drug use) and HIV co-infection. Immigrants from Sub-Saharan Africa, Asia and Eastern Europe had the highest HCV reported rates with RRs compared to non-immigrants ranging from 1.5 to 1.7. The age and sex adjusted rates decreased by 4.9% per year in non-immigrants but remained unchanged in immigrants. The proportion of HCV occurring in immigrants doubled over the study period from 5 to 11%. CONCLUSIONS: Immigrants from intermediate and high HCV prevalence countries are at increased risk for HCV and had a mean delay in diagnosis of almost 10 years after arrival suggesting that they may benefit from targeted HCV screening and earlier linkage to care.

Enteric disease episodes and the risk of acquiring a future sexually transmitted infection: a prediction model in Montreal residents.

OBJECTIVE: The sexual transmission of enteric diseases poses an important public health challenge. We aimed to build a prediction model capable of identifying individuals with a reported enteric disease who could be at risk of acquiring future sexually transmitted infections (STIs). MATERIALS AND METHODS: Passive surveillance data on Montreal residents with at least 1 enteric disease report was used to construct the prediction model. Cases were defined as all subjects with at least 1 STI report following their initial enteric disease episode. A final logistic regression prediction model was chosen using forward stepwise selection. RESULTS: The prediction model with the greatest validity included age, sex, residential location, number of STI episodes experienced prior to the first enteric disease episode, type of enteric disease acquired, and an interaction term between age and male sex. This model had an area under the curve of 0.77 and had acceptable calibration. DISCUSSION: A coordinated public health response to the sexual transmission of enteric diseases requires that a distinction be made between cases of enteric diseases transmitted through sexual activity from those transmitted through contaminated food or water. A prediction model can aid public health officials in identifying individuals who may have a higher risk of sexually acquiring a reportable disease. Once identified, these individuals could receive specialized intervention to prevent future infection. CONCLUSION: The information produced from a prediction model capable of identifying higher risk individuals can be used to guide efforts in investigating and controlling reported cases of enteric diseases and STIs.

Using age, triage score, and disposition data from emergency department electronic records to improve Influenza-like illness surveillance.

OBJECTIVE: Markers of illness severity are increasingly captured in emergency department (ED) electronic systems, but their value for surveillance is not known. We assessed the value of age, triage score, and disposition data from ED electronic records for predicting influenza-related hospitalizations. MATERIALS AND METHODS: From June 2006 to January 2011, weekly counts of pneumonia and influenza (P&I) hospitalizations from five Montreal hospitals were modeled using negative binomial regression. Over lead times of 0-5 weeks, we assessed the predictive ability of weekly counts of 1) total ED visits, 2) ED visits with influenza-like illness (ILI), and 3) ED visits with ILI stratified by age, triage score, or disposition. Models were adjusted for secular trends, seasonality, and autocorrelation. Model fit was assessed using Akaike information criterion, and predictive accuracy using the mean absolute scaled error (MASE). RESULTS: Predictive accuracy for P&I hospitalizations during non-pandemic years was improved when models included visits from patients ≥65 years old and visits resulting in admission/transfer/death (MASE of 0.64, 95% confidence interval (95% CI) 0.54-0.80) compared to overall ILI visits (0.89, 95% CI 0.69-1.10). During the H1N1 pandemic year, including visits from patients <18 years old, visits with high priority triage scores, or visits resulting in admission/transfer/death resulted in the best model fit. DISCUSSION: Age and disposition data improved model fit and moderately reduced the prediction error for P&I hospitalizations; triage score improved model fit only during the pandemic year. CONCLUSION: Incorporation of age and severity measures available in ED records can improve ILI surveillance algorithms.

Accuracy of prospective space-time surveillance in detecting tuberculosis transmission.

To improve detection of tuberculosis transmission, public health can supplement contact tracing with space-time surveillance. However, investigation of space-time clusters not due to transmission (false alarms), may lead to costly, unnecessary interventions. We measured the accuracy of prospective space-time surveillance in detecting tuberculosis transmission, assessing the number of clusters containing transmission and the false alarm rate. We simulated monthly prospective applications of a scan statistic using the home addresses and diagnosis dates of all 1566 culture-positive TB cases reported in Montreal during 1996-2007. We verified transmission within the space-time clusters by analyzing the TB genotype. Over 11.5 years, at 1.3 false alarms per month, we detected 89 transmission chains; at 0.05 false alarms per month we detected 5 transmission chains. We found evidence that prospective space-time surveillance for TB leads to a high false alarm rate, limiting its practical utility in settings with TB epidemiology similar to Montreal.

Challenges to the surveillance of meningococcal disease in an era of declining incidence in montréal, Québec.

OBJECTIVES: Though rare in Montréal, meningococcal disease continues to cause serious morbidity and mortality. In an era of declining incidence, our objective was to evaluate the sensitivity and the timeliness of case reporting and the capacity to statistically detect disease clusters. METHODS: We used the public health department's reportable disease database (RDD) to calculate the timeliness of reporting by physicians and laboratories for the period 1995 to 2008. The sensitivity of case reporting was evaluated through capture-recapture estimation using the RDD and the hospitalization discharge database (MED-ECHO). To evaluate the detection of cases clustered by time and proximity, we applied scan statistics to the RDD with cases coded by time and geographic location for the period 1992 to 2008. RESULTS: While the system sensitivity was judged to be high at 94%, physicians reported only 54% of cases. A total of 92.3% of cases were notified by physicians or laboratories within seven days, meaning that in theory, 13 cases were not notified in time to conduct thorough contact tracing and offer chemoprophylaxis to close contacts. In high-incidence years, scan statistics detected two statistically-significant clusters one to two weeks earlier than traditional detection through the manual monitoring of cumulative cases. CONCLUSIONS: To improve system performance, we recommended increasing the emphasis of laboratory reporting, reinforcing early reporting by physicians and if incidence increases, using scan statistics to identify clusters that can add to a public health practitioner's initial "hunch" of an emerging outbreak.

Completion rates of treatment for latent tuberculosis infection in Quebec, Canada from 2006 to 2010.

OBJECTIVE: Treatment of latent TB infection (LTBI) in high-risk populations has been identified as a priority activity for reducing TB incidence. Treatment completion rates are usually far from the 80% target. The objective of this study was to evaluate the proportion of individuals who obtained enough medication for standard LTBI treatment. METHODS: Using the Régie de l'assurance maladie du Québec database, we extracted data on all prescriptions filled as part of the free anti-tuberculosis medication program. We calculated the proportion of patients who had obtained at least 270 doses among patients who had started treatment with isoniazid (INH), and the proportion of patients who had obtained at least 120 doses among patients who had started treatment with rifampin (RMP). RESULTS: Among the 2,895 patients who had started INH, 907 (31.3%) obtained at least 270 doses. Among the 373 patients who had started RMP, 242 (64.9%) obtained at least 120 doses. Women were more likely to stop INH treatment before acquiring 270 doses of the medication than men (hazard ratio [HR] = 1.08; 95% confidence interval [CI]: 1.01-1.17). CONCLUSION: Only 31.3% of patients who started treatment with INH had procured at least 270 doses. Completion rates are far below target values.

Campylobacter coli outbreak in men who have sex with men, Quebec, Canada, 2010-2011.

During September 2010-November 2011, a cluster of erythromycin-susceptible, tetracycline- and ciprofloxacin-resistant Campylobacter coli pulsovar 1 infections was documented, involving 10 case-patients, in Montreal, Quebec, Canada. The findings suggested sexual transmission of an enteric infection among men who have sex with men.

Predictors of methadone program non-retention for opioid analgesic dependent patients.

This study evaluates loss to follow-up in a methadone maintenance treatment (MMT) program for patients dependent on opioid analgesics in a community in eastern Canada. Data were collected using the Addiction Severity Index Lite. The probability of loss to follow-up was evaluated using a time-to-event analysis. Involuntary and voluntary program discharges were treated separately as the outcomes of interest. Multivariate Cox proportional hazards models were used to explore the role of various patient-related attributes. The probabilities of involuntary and voluntary discharges at 1 year were 20% and 14%, respectively. In this exploratory analysis, determinants of loss to follow-up were characteristics related to drug use history (e.g., use of sedatives) and its consequences (e.g., number of lifetime arrests), and differed for each outcome. Some determinants of involuntary discharge were modified by sex. Understanding predictors of specific loss to follow-up outcomes may help MMT programs improve patient retention.

Examining the association between neighbourhood characteristics and gonorrhea rates among women aged 15 to 24 years in Montreal, Canada.

OBJECTIVE: The reported incidence rate of gonorrhea has more than doubled from 2000 to 2010 in Montréal, increasing in both sexes and all age groups; however, the increase was particularly high in females aged 15 to 24 years. As the reasons for this increase among young women are not fully understood, we wanted to determine whether neighbourhood-level population characteristics were associated with incidence rates in this group, to help target intervention strategies. METHODS: Incident gonorrhea cases were female residents of Montréal aged 15 to 24 years who met Québec's gonorrhea surveillance definition, with a notification date from 2002 to 2009. Adjusted incidence rate ratios (IRR) were estimated by negative binomial regression and show the change in the incidence of gonorrhea for each unit increase in neighbourhood-level independent variables, which included material and social deprivation indices (plus the latter's combination and components) and ethnic origin. In the final model, independent variables were normalized to facilitate comparison of their respective IRRs. RESULTS: A total of 837 cases were reported (cumulative incidence rate 5.6 per 100,000). Higher proportions of persons of African, Aboriginal and Caribbean ethnicity were associated with higher rates of gonorrhea, even after adjustment for deprivation indices. CONCLUSION: Customary methods for gonorrhea surveillance consider individual characteristics of cases as risk factors for disease. However, our results show that gonorrhea is clustered in neighbourhoods that have high proportions of three ethnic origin groups. Findings from this ecological approach suggest that although ethnicity may be strongly correlated with socio-economic status, there are factors in ethnicity that transcend poverty.

Community-acquired Clostridium difficile-associated diarrhea, Montréal, 2005-2006: frequency estimates and their validity.

A retrospective search for community-acquired Clostridium difficile-associated diarrhea in 15 hospitals revealed important discrepancies with numbers for the same period reported in real time to the surveillance system. Several of the observed problems could be solved by implementing case-by-case notification with subsequent investigation by local public health, as for other reportable diseases.

Trends in duration of hospitalization for patients with tuberculosis in Montreal, Canada from 1993 to 2007.

OBJECTIVE: To study the trend of hospital stays for patients diagnosed with pulmonary TB in Montreal from 1993 to 2007. METHODS: From the registry of hospital discharge summary information, we selected first hospitalizations for patients with a diagnosis of TB, and from the reportable diseases registry, patients with culture positive pulmonary TB. We linked the selected cases, using the first 3 characters of postal code of residence, sex and age. From the linked cases, we included those for whom date of patient's admission to hospital (from the former registry) was similar to the date of notification to the public health department (from the latter registry), while allowing for an appropriate variation. RESULTS: Among the 563 linked cases, the median duration of hospitalization was 17.0 days. Duration of hospitalization did not significantly decrease during the study period. Cases with positive sputum smear were more likely to stay in hospital > or = 14 days compared to those without one (OR = 1.90, 95% CI: 1.34-2.70). TB cases > or = 50 years of age remained in hospital longer than those between 18-49 years of age (OR = 1.66, 95% CI: 1.15-2.40). CONCLUSION: For 63.9% (360) of the cases studied, the duration of hospitalization was > or = 14 days, which is consistent with the minimum recommended hospital stay for patients with pulmonary TB in Canada. Further studies are necessary to examine the impact of discharging hospitalized TB patients before 14 days of hospital stay on the risk of TB transmission in the community.

The reported incidence of campylobacteriosis modelled as a function of earlier temperatures and numbers of cases, Montreal, Canada, 1990-2006.

Previous studies have detected an effect of earlier temperatures on the incidence of campylobacteriosis in humans, but without adjustment for earlier numbers of cases of the disease. We estimated the effect of temperature on the number of cases notified by week in Montreal, Canada, from 1 January 1990 to 26 March 2006, simultaneously with the effect of the numbers of cases notified in the preceding weeks. The current campylobacteriosis count (week 0) was modelled by negative binomial regression, with earlier weekly average temperatures and earlier counts as predictors. Secular trends were accounted for by cubic spline functions and seasonal variations by sine-cosine functions. Indicator variables identified weeks with fewer than 5 working days. In the final statistical model, a 1°C increase in temperature above 10°C during any of weeks -1 to -6 was associated with a 0.8% (95% CI: 0.3% to 1.3%) increase in the current count. For each additional notified case during any of weeks -1 to -5 or -9 to -12, the increase in the current count was approximately 0.5% (95% CI: 0.2% to 1.0%). Thus, earlier temperatures and earlier counts have independent effects, that of temperatures being the larger one. The temperature effect is too small to require short term public health planning. However, in Montreal, an increase in average temperature of the order of 4.5°C, forecast by some for 2055, could produce a 23% increase in incidence, resulting in about 4,000 excess cases per year.

Diabetes and the severity of pandemic influenza A (H1N1) infection.

OBJECTIVE: To confirm the existence of an increased risk of complications from influenza A (H1N1)p among patients with diabetes. RESEARCH DESIGN AND METHODS: Using data from an enhanced influenza surveillance project in Montreal, Canada, and age/sex-specific population estimates of diabetes prevalence, we estimated the risk of hospitalization among persons with diabetes. Comparing hospitalized patients admitted or not to an intensive care unit (ICU), we estimated the risk of ICU admission associated with diabetes, controlling for other patient characteristics. RESULTS: Among 239 hospitalized patients with PCR-confirmed influenza A (H1N1)p, 162 (68%) were interviewed, of whom 22 had diabetes, when 7.1 were expected (prevalence ratio 3.10 [95% CI 2.04-4.71]). The odds ratio for ICU admission was 4.29 (95% CI 1.29-14.3) among hospitalized patients with diabetes compared to those without. CONCLUSIONS: Diabetes triples the risk of hospitalization after influenza A (H1N1)p and quadruples the risk of ICU admission once hospitalized.

Estimating attributable mortality due to nosocomial infections acquired in intensive care units.

BACKGROUND: The strength of the association between intensive care unit (ICU)-acquired nosocomial infections (NIs) and mortality might differ according to the methodological approach taken. OBJECTIVE: To assess the association between ICU-acquired NIs and mortality using the concept of population-attributable fraction (PAF) for patient deaths caused by ICU-acquired NIs in a large cohort of critically ill patients. SETTING: Eleven ICUs of a French university hospital. DESIGN: We analyzed surveillance data on ICU-acquired NIs collected prospectively during the period from 1995 through 2003. The primary outcome was mortality from ICU-acquired NI stratified by site of infection. A matched-pair, case-control study was performed. Each patient who died before ICU discharge was defined as a case patient, and each patient who survived to ICU discharge was defined as a control patient. The PAF was calculated after adjustment for confounders by use of conditional logistic regression analysis. RESULTS: Among 8,068 ICU patients, a total of 1,725 deceased patients were successfully matched with 1,725 control patients. The adjusted PAF due to ICU-acquired NI for patients who died before ICU discharge was 14.6% (95% confidence interval [CI], 14.4%-14.8%). Stratified by the type of infection, the PAF was 6.1% (95% CI, 5.7%-6.5%) for pulmonary infection, 3.2% (95% CI, 2.8%-3.5%) for central venous catheter infection, 1.7% (95% CI, 0.9%-2.5%) for bloodstream infection, and 0.0% (95% CI, -0.4% to 0.4%) for urinary tract infection. CONCLUSIONS: ICU-acquired NI had an important effect on mortality. However, the statistical association between ICU-acquired NI and mortality tended to be less pronounced in findings based on the PAF than in study findings based on estimates of relative risk. Therefore, the choice of methods does matter when the burden of NI needs to be assessed.

Upsurge of chlamydial reinfection in a large Canadian city: an indication of suboptimal chlamydia screening practices?

OBJECTIVES: Given the limited knowledge on chlamydial reinfection (CR) in Canada, we examined the extent and predictors of CR in Montréal, a large Canadian city. METHODS: We retrospectively studied all Montréal residents aged > or =10 years for whom > or =1 laboratory-confirmed chlamydial infection was reported to the public health department between 1988 and 2007 (n = 44,580). Each person was passively followed for two years after baseline infection or until reinfection. Socio-demographic factors and histories of other notifiable diseases were examined as potential predictors. Cox multivariate regression was used to model the time to CR. Survival analyses were stratified by age group (<25 vs. > or =25 years). RESULTS: We estimated an overall two-year CR rate of 6.4%, an incidence density of 3.5 per 100 person-years, and a median time to reinfection of nine months. CR significantly increased over time. Among persons <25 years, reinfection was significantly more likely among females [adjusted hazard ratio (AHR): 1.58] and younger participants (10-14 years: AHR: 2.98; 15-19 years: AHR: 1.81). Residing within the South Central sector was deleterious for six months following initial infection after which it became protective. Among persons > or =25 years, a history of sexually transmitted infections increased the risk of reinfection (AHR: 1.79). CONCLUSION: CR is a significant and growing problem in Montreal. The current recommendation for a single repeat screening six months posttreatment might be usefully complemented with additional screenings. Our results also underscore the importance of screening high-risk populations, particularly young women.

Residential address errors in public health surveillance data: a description and analysis of the impact on geocoding.

The residential addresses of persons with reportable communicable diseases are used increasingly for spatial monitoring and cluster detection, and public health may direct interventions based upon the results of routine spatial surveillance. There has been little assessment, however, of the quality of address data in reportable disease notifications and of the corresponding impact of these errors on geocoding and routine public health practices. The objectives of this study were to examine address errors for a selected reportable disease in a large urban center in Canada and to assess the impact of identified errors on geocoding and the estimated spatial distribution of the disease. We extracted data for all notifications of campylobacteriosis from the Montreal public health department from 1995 to 2008 and used an address verification algorithm to determine the validity of the residential address for each case and to suggest corrections for invalid addresses. We assessed the types of address errors as well as the resulting positional errors, calculating the distance between the original address and the correct address as well as changes in disease density. Address errors and missing addresses were prevalent in the public health records (10% and 5%, respectively) and they influenced the observed distribution of campylobacteriosis in Montreal, with address correction changing case location by a median of 1.1 km. Further examination of the extent of address errors in public health data is essential, as is the investigation of how these errors impact routine public health functions.