Patterns and characteristics of TB among key risk groups in Canada, 1993-2018.

BACKGROUND: Canada has a low incidence of TB, although certain groups are disproportionately affected.OBJECTIVE: To describe and compare the epidemiology, trends and characteristics of TB in Quebec, Canada, among all patients reported during 1993-2018.METHODS: Demographics and risk factors were compared for the three groups accounting for most TB diagnoses reported in Quebec (foreign-born, Canadian-born non-Indigenous and Inuit). Average annual incidence and incidence rate ratios (IRRs) were estimated and compared using Poisson regression.RESULTS: Of 6,941 persons with a first episode of TB, 4,077 (59%) were foreign-born, 2,314 (33%) were Canadian-born non-Indigenous and 389 (6%) were Inuit. The average annual incidence for foreign-born, Canadian-born non-Indigenous and Inuit was respectively 17.0, 1.4 and 137.1 per 100,000 population. Compared to Canadian-born non-Indigenous, the IRR for foreign-born and Inuit was respectively 12.3 (95% CI 11.6-12.9) and 98.7 (95% CI 88.6-109.9). There was evidence of community transmission among the Inuit, with more than 80% of patients having a TB contact (2012-2018 data) and 65% (251/389) of diagnoses in those aged <25 years.CONCLUSION: Although TB rates among the Canadian-born non-Indigenous are extremely low, there are persistent and distinct TB epidemics among the foreign-born and Inuit. Tailored approaches to TB prevention and care are needed to address TB among high-risk populations in low TB incidence settings.

Outbreak of tuberculosis among substance users and homeless people in Greater Montréal, Canada, 2003-2016.

BACKGROUND: In Canada, active tuberculosis (TB) is found mainly among migrants from endemic countries and Indigenous populations. However, cases of active tuberculosis in substance users and homeless persons have been reported in Greater Montréal since 2003. OBJECTIVE: To describe the Montréal TB outbreak in terms of the sociodemographic characteristics, risk factors and clinical characteristics of cases, as well as the intensity of public health interventions, the follow-up and identification of locations of potential transmission. METHODS: All cases of active tuberculosis with the same genotype of interest residing in Quebec and epidemiologically linked cases were included in the analysis. Data were retrospectively extracted from routine public health investigations. Characteristics of cases were summarized using Excel. Spatial analysis of locations frequented during cases' infectiousness periods was performed. RESULTS: Between January 2003 and February 2016 a total of 35 cases were identified. Most (86%) were non-Indigenous people born in Canada. Of these, 28 had several risk factors, including substance use (93%), alcohol abuse (64%), homelessness (46%), comorbidities such as HIV coinfection (36%) and advanced stage of the disease. Seven cases without risk factors were all close contacts of cases. Intensity of case management by public health authorities was high. Locations frequented by cases with risk factors included crack houses, shelters and rehabilitation centers in Montréal's downtown core and a residential setting in a suburban area. CONCLUSION: TB outbreaks can occur in marginalized Canadian-born urban populations, especially those with substance use. Tailored interventions in this population may be needed for screening, and earlier identification of both latent and active TB and better linkage to care.

Screening employees of services for homeless individuals in Montréal for tuberculosis infection.

The results of a tuberculin skin test (TST) screening program offered to employees of services for homeless people in Montréal from 1998 to 2005 were analyzed to assess the occupational risk of tuberculosis (TB) infection. Employees with no known contact with TB were selected among volunteer participants. They were followed in two dynamic cohorts: individuals with a negative two-step baseline TST (cohort A) and individuals with a negative single baseline TST (cohort B). We estimated the prevalences of initial positive TST, boosting effect, and conversion rate. The average age of the workers was 38.9 years. The prevalence of an initial positive TST was 12.9%. A booster effect was observed in 5.1% of workers who completed a two-step TST. The incidence of conversion was 2.3/100 person-years for cohort A (n=93) and 3.5/100 person-years for cohort B (n=221). The incidence of conversion was not significantly associated with any of the demographics or workplace factors investigated. Our findings are comparable to the rates reported among community workers, whose risk is higher than the average health worker. This suggests that there are occasional unidentified contagious cases among the homeless individuals of participating institutions.

Mycobacterium tuberculosis transmission over an 11-year period in a low-incidence, urban setting.

SETTING: Montreal, Canada, has a mean annual tuberculosis (TB) incidence of 9 per 100,000 population, 1996-2007. OBJECTIVE: To characterise potential Mycobacterium tuberculosis transmission by patient subgroups defined by age, sex, birthplace, smear and human immunodeficiency virus status, and to estimate the proportion of cases that resulted from transmission between these patient subgroups. DESIGN: Retrospective study using DNA fingerprinting techniques, with clinical and demographic information from the public health department. Among cases with matching fingerprints, a pulmonary index case was identified. The transmission index was defined as the average number of subsequent TB cases generated directly or indirectly from an index case, and was compared among subgroups, including Haitian immigrants. RESULTS: Compared to non-Haitian foreign-born index cases, Canadian-born index cases were associated with 2.38 times as many (95%CI 1.24-4.58) subsequent cases, while Haitian-born index cases were associated with 3.58 times as many (95%CI 1.74-7.36). Smear-positive index cases were not independently associated with increased transmission. However, middle-aged Canadian-born index patients were associated with a disproportionate number of subsequent cases. CONCLUSION: In Montreal, index patients from several high-risk groups are associated with subsequent transmission. This approach can be applied to other low-incidence settings to identify where targeted interventions could potentially further reduce transmission.

Severe complications associated with varicella: Province of Quebec, April 1994 to March 1996.

OBJECTIVE: To determine the frequency and severity of serious complications associated with varicella in Quebec; the frequency and severity of cases of congenital varicella; and hospital costs associated with hospitalizations for varicella. STUDY DESIGN: All hospitalizations related to varicella were identified through the use of a hospital data bank and pertinent data were collected from hospital records. SETTING: Province of Quebec with a population of 6,895,960 people. STUDY POPULATION: All cases with a principal or secondary diagnosis of varicella hospitalized in Quebec between April 1, 1994 and March 31, 1996. OUTCOME MEASURES: Types of complications and reason for hospitalization, risk of complications and calculation of associated costs were studied. RESULTS: Nine hundred nine eligible hospitalizations were identified between April 1, 1994 and March 31, 1996. In all, 583 (64.1%) hospitalizations were for the treatment of complications, 127 (14.0%) for administration of intravenous acyclovir and 199 (21.9%) for supportive care. Healthy people accounted for 644 (70.8%) hospitalizations and immunosuppressed individuals for 136 (15.0%). Among children, one-half of the principal complications were skin infections, while 13.5% and 8.4% of principal complications were pneumonia and neurological complications, respectively. Among adults, the most common complication was pneumonia, with a rate of 43.5%, followed by thrombocytopenia and skin infections, with rates of 22.2% and 14.8%, respectively. The complication rate was 29.2 cases/10,000 cases of varicella. CONCLUSIONS: Although perceived as a benign childhood disease by the general population, varicella may be accompanied by severe complications. Morbidity associated with varicella is one of the elements that must be considered when evaluating the usefulness of varicella vaccine.

Initial drug regimen for active tuberculosis cases in Montreal, 1995 to 1998.

OBJECTIVES: To evaluate the proportion of tuberculosis (TB) cases initially treated with the recommended four-drug regimen of isoniazid (INH), rifampin (RIF), pyrazinamide (PZA) and ethambutol (EMB) or streptomycin; and to identify factors associated with the choice of initial therapy. DESIGN: Descriptive analysis of surveillance data obtained by TB case notifications from physicians and microbiology laboratories. SETTING: The island of Montreal (with a population of 1,854,435 people). STUDY POPULATION: All TB cases reported between January 1, 1995 and December 31, 1998. OUTCOME MEASURE: The proportion of TB cases initially treated with a four-drug regimen by sex, age, country of birth, site of disease and year of reporting. MAIN RESULTS: Seven hundred forty-one cases were reported during the study period. Among the 687 analyzed cases, 406 (59.1%) received the recommended initial four-drug regimen (INH-RIF-PZA-EMB), 187 (27.2%) received an INH-RIF-PZA regimen, 61 (8.9%) received an INH-RIF-EMB regimen and 33 (4.8%) received an INH-RIF regimen only. In a logistical regression model, a four-drug regimen was significantly associated with respiratory disease (odds ratio [OR] 4.48; 95% CI 3.15 to 6.39), age younger than 65 years (OR 2.32; 95% CI 1.55 to 3.45), being foreign-born (OR 1.62; 95% CI 1.06 to 2.48) and later year of reporting (OR 1.27; 95% CI 1.09 to 1.47). CONCLUSIONS: The proportion of TB cases initially treated with a four-drug regimen has increased steadily since 1995, reaching 65% in 1998. However, given the rate of INH resistance in Montreal, efforts to promote the use of the initial four-drug regimen must continue.

Epidemiology of tuberculosis in Montreal.

OBJECTIVE: To identify the epidemiologic characteristics of tuberculosis (TB) in Montreal and the patterns of resistance to antituberculous drugs in order to improve TB control in the region. DESIGN: Descriptive analysis of surveillance data for TB cases reported in Montreal by physicians and laboratories between 1992 and 1995. SETTING: Region of Montreal, population 1,775,889. PARTICIPANTS: All cases of active TB among Montreal residents reported to the Department of Public Health between Jan. 1, 1992, and Dec. 31, 1995. OUTCOME MEASURES: Epidemiologic characteristics, proportion of cases resistant to antituberculous drugs and types of resistance. RESULTS: A total of 798 cases of TB (mean annual incidence 11.2 per 100,000) were reported in Montreal during the study period. Of these patients, 617 (77.3%) were born outside Canada. The annual incidence of TB in the foreign-born population (37.5 per 100,000) was 10 times the rate in the Canadian-born population, and the highest rate among foreign-born residents (62.8 per 100,000) occurred in those 15-29 years of age. In general, annual incidence in Montreal's foreign-born population reflected the reported incidence of TB in their regions of birth. In 8.7% of all cases, the disease was resistant to isoniazid, and the proportion of cases resistant to this drug was greater than 4% in almost all age groups, among both foreign-born and Canadian-born patients. CONCLUSIONS: TB remains a major problem in Montreal, as in other large cities. Surveillance data give opportunities to public health agencies to adapt their prevention and control strategies to local situations and can also help clinicians in their clinical decision-making.

Risk factors for measles and vaccine efficacy during an epidemic in Montreal.

OBJECTIVES: 1) to identify potential risk factors for measles and 2) to assess the efficacy of the measles vaccine. METHODS: Cases of measles reported from primary and secondary schools in Montreal during the 1989 epidemic were compared with classroom and sibling controls with respect to age at vaccination against measles, time since vaccination, type of vaccination, type of providers and age of the mother. RESULTS: Subjects vaccinated at 12 months had an OR of 3.9 (CI 95%: 2.1 to 7.0) of contracting measles when compared with subjects vaccinated at 15 months or later. Vaccination at age 13 or 14 months was not associated with an increased risk. Subjects vaccinated before June 1979 had an OR of 5.8 (CI 95%: 2.8 to 12.1) of developing measles compared with subjects vaccinated after June 1980. Vaccine efficacy was 96.1%. DISCUSSION: In highly vaccinated populations, vaccination at 12 months and vaccination before 1980 are probably two reasons why outbreaks still occur. The two-dose schedule could reduce the proportion of vaccinated persons who remain susceptible.

[Tuberculin screening in a secondary school in Montreal following a case of pulmonary tuberculosis]. / Dépistage tuberculinique dans une école secondaire de Montréal suite à un cas de tuberculose pulmonaire.

We planned a tuberculin testing in a secondary school, following student exposure to a fellow student suffering from pulmonary tuberculosis. A first group of 71 students for whom exposure seemed greater, had an intradermal Mantoux test. Of these 71 students, 18 (25.3%) had a > or = 5 mm reactions; 52 went through a second test three months later, six of whom had a > or = 5 mm reaction. In light of the results of the screening in this first group, the tuberculin testing was offered to a second group of 108 students. In this second group, the result of the skin test was > or = 5 mm for 10 (9.3%) students. Out of 179 students, 34 (19.0%) had a significative reaction. A > or = 5 mm reaction was significantly associated with being male, being born outside of Québec and being a member of the first group screened.

Do conventional and innovative medical schools recruit different students?

A mail questionnaire was used to survey the social and demographic characteristics, educational background, attitudinal profiles and expected career choice of 243 first-year students enrolled in three US medical schools. The aim was to determine whether different types of schools selected different types of students. Two schools were considered as conventional whereas one school was considered as innovative both in its admission policies and in its curriculum which emphasizes a biopsychosocial approach to health care. The survey achieved an 84% response rate. The results showed no difference in students' career expectations. Students recruited in the innovative school, however, differed from students recruited in the conventional schools with regard to their social and demographic characteristics, educational background and attitudinal profiles. This study suggests that as some medical schools are innovating in their curriculum and admission policies, new types of medical students are entering medicine. Implications of these results are discussed.

Nonshivering thermogenesis and cold resistance in rats under severe cold conditions.

Following either chronic exposure to 6 degrees C, or outdoor winter exposure, or chronic treatment with tyramine rats were exposed to -40 degrees C and their oxygen consumption and colonic temperature monitored. Fall in body temperature with time of exposure followed a sigmoid curve which had an inflection point around 32.9 degrees C. Both the time required for body temperature to reach this point and hypothermic resistance defined as the total O2 consumed up to the inflection time were useful indices of resistance to severe cold; Three days before the cold tests, capacity for norepinephrine-induced nonshivering thermogenesis was measured in all animals by examination of their metabolic response to tyraminemthe magnitude of response to tyramine correlated well with hypothermic resistance only for those rats chroncally treated with tyramine. It is concluded that it is impossible to predict with any reasonable degree of confidence the cold resistance of a rat from its tyramine response. In cold-acclimated rats, factors in addition to norepinephrine sensitivity are significantly involved in cold resistance and deserve further studies.