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.

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]

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.

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.