Tuberculosis in recent Asian immigrants to British Columbia, Canada: 1982–1985

doi:10.1016/0041-3879(91)90054-V

Tubercle

Volume 72, Issue 4, December 1991, Pages 277-283

Tubercle

https://doi.org/10.1016/0041-3879(91)90054-V Get rights and content

Abstract

The prevalence and incidence of active tuberculosis among 21 959 recently arrived (1982–1985) immigrants from 7 selected Asian countries into British Columbia (BC), Canada, were reviewed. Among these newly arrived immigrants, 1173 (5.3%) were judged to have inactive tuberculosis at the immigration examination in their country of origin. In this subgroup, 14 of 932 (1.5%) were found to have active tuberculosis at the initial examination after arrival in Canada. Subsequently, 7 further cases arose in this group of inactive cases giving an average annual incidence rate of 0.33% over the 4-year period of study. Only 3 of these 21 cases had previous antituberculosis chemotherapy. The remaining 20 786 recent immigrants with normal X-rays at the immigration examination contributed 30 cases during the next 4 years — an average annual incidence rate of 0.08% or 8 times the comparable rate for BC (0.01%).

The limitations of the immigration screening process are illustrated and the value of early surveillance of immigrants designated as having inactive tuberculosis is underlined. The apparent failure to exclude active disease prior to the arrival of these immigrants is one factor elevating the incidence of active tuberculosis in the first few years after arrival in the host country. Other factors include the relatively high prevalence of inactive tuberculosis among the immigrants from certain countries and their high rate of early relapse after entry, especially in those not previously treated. Such immigrants should be considered for chemoprophylaxis immediately after entry.

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Cited by (38)

Effectiveness of Canada's tuberculosis surveillance strategy in identifying immigrants at risk of developing and transmitting tuberculosis: a population-based retrospective cohort study
2017, The Lancet Public Health
Citation Excerpt :
Referrals either had evidence of old, healed tuberculosis on chest radiograph or a history of tuberculosis. They might have achieved some degree of accommodation27 with their tuberculosis infection, which might render their active disease less severe and less infectious. This theory was originally posited by Toman in 1979,28 when he noted that “[t]he hypothesis that all cases (of active pulmonary TB) could be detected at an early stage by x-raying the entire population at intervals of a few years (assumes) that tuberculosis in adults starts as a rule with a minimal lesion ‘early infiltrate’ that—without treatment—would all develop step by step into advanced, smear-positive tuberculosis.
In Canada, tuberculosis disproportionately affects the foreign-born population. The national tuberculosis medical surveillance programme aims to prevent these cases. Individuals referred for further in-country surveillance (referrals) have a history of active tuberculosis or have features of old, healed tuberculosis on chest radiograph; those not referred (non-referrals) do not undergo surveillance. We aimed to examine the risk of transmission arising from referrals versus non-referrals.
We did this population-based retrospective cohort study of foreign-born migrants (aged 15–64 years) to Alberta, Canada, between Jan 1, 2002, and Dec 31, 2013. We obtained information about year of arrival and country of citizenship from Immigration, Refugees and Citizenship Canada, and data for tuberculosis cases and their contacts from the Alberta Tuberculosis Registry. The outcome of interest was culture-positive pulmonary tuberculosis. We compared the incidence of pulmonary tuberculosis and the odds of transmission among referrals versus non-referrals. By use of conventional and molecular epidemiological techniques, we defined transmission as either a secondary case or a tuberculin skin-test (TST) conversion among close contacts. We used multivariate logistic regression to determine the independent association between referral for tuberculosis surveillance and transmission.
Between 2002 and 2013, there were 223 225 foreign-born migrants to Alberta, of whom 5500 (2%) were referrals and 217 657 (98%) were non-referrals. 3805 (69%) referrals and 115 226 (53%) non-referrals were from countries with a tuberculosis incidence of more than 150 per 100 000 populations, or sub-Saharan Africa. 234 foreign-born individuals were diagnosed with culture-positive pulmonary tuberculosis between Jan 1, 2004, and Dec 31, 2013. The incidence of culture-positive pulmonary disease was nine times higher in referrals (n=50) than all non-referrals (n=184; incidence rate ratio 9·1, 95% CI 6·7–12·5) and five times higher in referrals than non-referrals from high-risk countries (n=167; 5·0, 3·6–6·8). 71 total transmission events arose from the individuals with culture-positive pulmonary tuberculosis—three (4%) from referrals and 68 (96%) from non-referrals. No secondary cases were attributable to a referral source case, whereas 18 secondary cases were attributable to 11 different non-referral source cases. Three TST conversions were attributable to three different referral source cases compared with 50 conversions from 31 different non-referral source cases. That is, three (6%) referrals transmitted tuberculosis compared with 42 (22%) non-referrals (adjusted odds ratio of 0·19, 95% CI 0·054–0·66; p=0·009).
Despite a much higher incidence of pulmonary tuberculosis in referrals than non-referrals, referrals were 80% less likely to transmit tuberculosis. Rather than a focus on referrals, Canada could consider screening and treatment of latent tuberculosis in all migrants from high-risk countries—a group that accounted for 100% of secondary cases.
Canadian Institutes of Health Research.
Post-migration follow-up of migrants identified to be at increased risk of developing tuberculosis at pre-migration screening: a systematic review and meta-analysis
2017, The Lancet Infectious Diseases
Citation Excerpt :
A summary of outcomes measures is presented in table 2. The pooled cumulative incidence of tuberculosis was 2794 per 100 000 high-risk migrants (95% CI 2179–3409; 2·8%; I2=99%) in 19 studies reporting on 22 cohorts (figure 2).19–37 Point estimates for the cumulative incidence of tuberculosis ranged from 521 per 100 000 persons25 to 7032 per 100 000 persons.21
Post-migration follow-up of migrants considered at increased risk of developing tuberculosis based on pre-migration screening abnormalities (high-risk migrants) is implemented in several low-incidence countries. We aimed to determine the rate of tuberculosis in this population to inform cross-border tuberculosis control policies.
We searched MEDLINE and Embase (since inception to Jan 12, 2017) for studies evaluating post-migration follow-up of high-risk migrants. Outcomes evaluated were the number of tuberculosis cases occurring post-migration, expressed as the tuberculosis incidence per 100 000 person-years of follow-up, as cumulative incidence of tuberculosis per 100 000 persons, and the cumulative incidence of tuberculosis at the first post-migration follow-up visit. Random-effects models were used to summarise outcomes across studies.
We identified 20 publications (describing 23 study cohorts) reporting the pre-migration screening outcomes of 8 355 030 migrants processed between Jan 1, 1981, and May 1, 2014, with 222 375 high-risk migrants identified. The pooled cumulative incidence of tuberculosis post-migration in our study population from 22 cohorts was 2794 per 100 000 persons (95% CI 2179–3409; I²=99%). The pooled cumulative incidence of tuberculosis at the first follow-up visit from ten cohorts was 3284 per 100 000 persons (95% CI 2173–4395; I²=99%). The pooled tuberculosis incidence from 15 cohorts was 1249 per 100 000 person-years of follow-up (95% CI 924-1574; I²=98%).
The high rate of tuberculosis in high-risk migrants suggests that tuberculosis control measures in this population, including more sensitive pre-migration screening, preventive treatment of latent tuberculosis infection, or post-migration follow-up, are potentially effective cross-border tuberculosis control strategies in low-incidence countries.
Australian National Health and Medical Research Council.
Pre-entry screening programmes for tuberculosis in migrants to low-incidence countries: A systematic review and meta-analysis
2014, The Lancet Infectious Diseases
Several high-income countries have pre-entry screening programmes for tuberculosis. We aimed to establish the yield of pre-entry screening programmes to inform evidence-based policy for migrant health screening.
We searched six bibliographic databases for experimental or observational studies and systematic reviews, which reported data on migrant screening for active or latent tuberculosis by any method before migration to a low-incidence country. Primary outcomes were principal reported screening yield of active tuberculosis, yield of culture-confirmed cases, and yield of sputum smear for acid-fast bacilli cases. Where appropriate, fixed-effects models were used to summarise the yield of pre-entry screening across included studies.
We identified 15 unique studies with data for 3 739 266 migrants screened pre-entry for tuberculosis between 1982 and 2010. Heterogeneity was high for all primary outcomes. After stratification by prevalence in country of origin, heterogeneity was reduced for culture-confirmed and smear-confirmed cases. Yield of culture-confirmed cases increased with prevalence in the country of origin, and summary estimates ranged from 19·7 (95% CI 10·3–31·5) cases identified per 100 000 individuals screened in countries with a prevalence of 50–149 cases per 100 000 population to 335·9 (283·0–393·2) per 100 000 in countries with a prevalence of greater than 350 per 100 000 population.
Targeting high-prevalence countries could result in the highest yield for active disease. Pre-entry screening should be considered as part of a broad package of measures to ensure early diagnosis and effective management of migrants with active tuberculosis, and be integrated with initiatives that address the health needs of migrants.
Wellcome Trust, UK National Institute for Health Research, Medical Research Council, Public Health England.
Mandatory screening and treatment of immigrants for latent tuberculosis in the USA: Just restraint?
2001, Lancet Infectious Diseases
A report by the Institute of Medicine, Ending Neglect, and sponsored by the US Centers for Disease Control and Prevention, makes recommendations for achieving elimination of tuberculosis in the USA. Among them is the recommendation that a mandatory screening programme be introduced for latent tuberculosis infection in immigrants from high prevalence countries, and that the provision of a permanent residence card (green card) be linked to the completion of an approved course of preventive treatment. We examine the evidence put forward to support this proposal and assess whether such a mandatory programme for preventive treatment of individuals, who do not pose an immediate risk but could pose a risk in the future, meets internationally recognised standards for coercive public-health measures. We conclude from our analysis that there is reason to question (i) the risk analysis, (ii) the estimates of effectiveness of such a policy, (iii) the cost calculations, and (iv) the operational consequences put forward in the report. Moreover, we show that international standards for mandatory screening and treatment are not met.
Mycobacterium tuberculosis disease in Somali immigrants in Minnesota
2001, Chest
Citation Excerpt :
Lymphadenitis was alsothe most common manifestation in the Somalis, affecting 58% ofextrapulmonary cases. Previous studies have shown that immigrants classified as havinginactive disease at the time of screening in their country of originfrequently have active disease when initially evaluated in theirdestination country.1635 Minnesota's aggressivesurveillance program for the identification of new TB cases coupledwith heightened clinical suspicion for TB among community caregiverswhen evaluating Somalis likely contributes to the higher incidenceobserved in the study.
To characterize pulmonary andextrapulmonary Mycobacterium tuberculosis cases in the, Somali community in Minnesota.
Retrospectivechart review of active tuberculosis cases in Somalis reported to the, Minnesota Department of Health between January 1993 and June 1998.
Ethnic Somalis in the state of Minnesota withM tuberculosis diagnosed by positive culture orradiographic findings consistent with tuberculosis and clinicalimprovement when treated with antituberculous drugs.
Eighty-two Somali patients werediagnosed with tuberculosis during the study period. Extrapulmonarydisease (typically lymphadenopathy) was present in 46% (n = 38). The1997 incidence of tuberculosis in Minnesota's Somali population wasestimated at 170 cases per 100,000 population compared with a nationalincidence of 20.5 per 100,000 among African Americans and 2.5 per100,000 among whites. Ninety percent of Somali patients were < 40years of age; 63% were diagnosed within 1 year of immigration, and>90% had positive results with the purified protein derivative skintest. M tuberculosis was confirmed in 24 of 25 isolatesfrom extrapulmonary cases. Multidrug resistance was present in 3.4%,and only two patients had AIDS.
Somalishave a high incidence of active disease, with frequent extrapulmonaryinvolvement in the absence of AIDS, clinical presentation shortly afterimmigration, and infrequent infection with resistant organisms. Health-care providers should maintain an increased awareness fortuberculosis when evaluating Somali immigrants.
A model for tuberculosis with exogenous reinfection
2000, Theoretical Population Biology
Following primary tuberculosis (TB) infection, only approximately 10% of individuals develop active T.B. Most people are assumed to mount an effective immune response to the initial infection that limits proliferation of the bacilli and leads to long-lasting partial immunity both to further infection and to reactivation of latent bacilli remaining from the original infection. Infected individuals may develop active TB as a consequence of exogenous reinfection, i.e., acquiring a new infection from another infectious individual. Our results in this paper suggest that exogenous reinfection has a drastic effect on the qualitative dynamics of TB. The incorporation of exogenous reinfection into our TB model allows the possibility of a subcritical bifurcation at the critical value of the basic reproductive number $R$ ₀=1, and hence the existence of multiple endemic equilibria for $R$ ₀<1 and the exogenous reinfection rate larger than a threshold. Our results suggest that reducing $R$ ₀ to be smaller than one may not be sufficient to eradicate the disease. An additional reduction in reinfection rate may be required. These results may also partially explain the recently observed resurgence of TB.

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^∗: International Development Research Centre Scholar. Present address: Director, Tuberculosis Centre, 124 Chifeng Road, Tianjin 300041, PR. China.

^†: Present address: International Union Against Tuberculosis and Lung Disease, 68 Boulevard Saint-Michel, 75006 Paris, France.

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Original articleTuberculosis in recent Asian immigrants to British Columbia, Canada: 1982–1985

Abstract

Tubercle

Clin Chest Med

Medical Officers Handbook

Classifccation and Reporting of Tuberculosis in Canada

Reactivatioms in inactive pulmonary tuberculosis

Am Rev Respir Dis

Tuberculosis among patients with various radiologic abnormalities, followed by the chest clinic service

Am Rev Respir Dis

Lifelong follow-up of inactive tuberculosis: its value and limitations

Am Rev Respir Dis

The influence of immigration on tuberculosis in Ontario

Am Rev Respir Dis

Original article
Tuberculosis in recent Asian immigrants to British Columbia, Canada: 1982–1985