Elsevier

The Lancet

Volume 356, Issue 9228, 5 August 2000, Pages 461-465
The Lancet

Articles
Risk of infection with Mycobacterium tuberculosis in travellers to areas of high tuberculosis endemicity

https://doi.org/10.1016/S0140-6736(00)02554-XGet rights and content

Summary

Background

No data exist on risks of infection with Mycobacterium tuberculosis in travellers. We studied incidences of and risk factors for tuberculin skin-test conversion among Dutch long-term travellers to countries of high tuberculosis endemicity.

Methods

In a multicentre, prospective cohort study based in travel and tuberculosis clinics in the Netherlands, 1072 BCG-naïve immunocompetent travellers to countries with an estimated annual risk of M tuberculosis infection of at least 1% were skin tested before departure with 1 tuberculin unit purified protein derivative (PPD) of M tuberculosis in Tween-80. Those with results less than 2 mm were retested 2–4 months after their return with simultaneous testing for cross-sensitivity to environmental mycobacteria (1 tuberculin unit PPD of M scrofulaceum in Tween-80). M tuberculosis infection was defined as a post-travel M tuberculosis tuberculin skin-test result of at least 10 mm that was 3 mm or more larger than the M scrofulaceum result.

Findings

Post-travel skin-test results were available for 656 (66%) of 988 individuals who were eligible for follow-up. Among these, 12 M tuberculosis infections were identified (1·8%). The overall incidence rate was 3·5 per 1000 person-months of travel (95% Cl 2·0–6·2), and 2·8 per 1000 person-months of travel (1·2–5·5) after exclusion of health-care workers. Two had active tuberculosis at the time of testing (incidence rate 0·6 per 1000 person-months of travel [0·3–2·3]). Work in patient care abroad was an independent risk factor (adjusted rate ratio 5·34, p=0·015).

Interpretation

The risk of M tuberculosis infection in long-term travellers to high-endemicity countries, even if not engaged in health-care work, is substantial and of similar magnitude to the average risk for the local population. BCG vaccination or post-travel tuberculin skin-testing of high-risk travellers should be considered.

Introduction

International travel and migration increase the spread of infectious diseases such as cholera, dengue, and AIDS.1, 2 Tuberculosis—a disease still highly endemic in large parts of the world—also has the potential for introduction into and further transmission within countries where it has become rare.3 Of particular concern is the spread of drugresistant strains.4 International travellers to highendemicity areas have received little attention as a possible source of introduction of tuberculosis. In some countries where vaccination with BCG is not given routinely, including the Netherlands, selected travellers are routinely advised to have tuberculin skin tests to identify recent infections. Compliance with such screening programmes is low, and little is known about cost-effectiveness, primarily because of lack of data on the risk of Mycobacterium tuberculosis infection during international travel.5, 6 The risk of tuberculosis in travellers is difficult to determine, because of the wide range in incubation periods of active infection, the low lifetime risk of active disease after infection, differences in background prevalence of latent infections, and the limited specificity of tuberculin testing after vaccination with BCG and in populations with high rates of non-specific reactions.7, 8, 9, 10 To quantify the risk of M tuberculosis infection in international travel, we estimated the rate of tuberculin skin-test conversion in a multisite cohort of BCG-naïve, skin-test-negative Dutch travellers who intended to stay for 3–12 months in areas of high tuberculosis endemicity.

Section snippets

Study population

All travellers born in the Netherlands after Dec 31, 1944, and who were at least 15 years old were eligible if they had not received BCG vaccination and intended to travel for a period of 3–12 months to countries highly endemic for tuberculosis. Such countries were defined as those with a reported or estimated annual incidence of tuberculosis of 1% or more.11 BCG status was ascertained by history, inspection for typical scars, and, in case of doubt, checking against the BCG registry. Exclusion

Results

Of 1072 individuals initially included, 988 were eligible for follow-up (figure). A post-travel M tuberculosis PPD result was available for 656 (66·4%). Of these, 616 (93·9%) were done with 1 tuberculosis unit PPD, and 40 with 2 tuberculosis units Rt23; an M scrofulaceum PPD post-travel test result was available for 618 (94·2%). For 32 individuals (4·9%), results of M tuberculosis PPD tests done elsewhere were used. Seven post-travel tests were repeated (1·1%). The mean age of the 656

Discussion

The risks of latent M tuberculosis infection in travellers found in this study, both overall and for non-health-care workers (3·5 and 2·8 per 1000 person-months of travel), are similar to those of hepatitis A in holiday makers or of malaria in tourists to Kenya, but are several-fold higher than the incidence rates of most other vaccine-preventable infections, including typhoid fever, cholera, and meningococcal disease.1, 14, 15, 16, 17 For non-health-care workers, the average annual incidence

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