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Air-travel related TB incident follow up - effectiveness and outcomes: a systematic review.

BACKGROUND
The World Health Organization (WHO) recommends following up passengers following possible exposure to a case of infectious tuberculosis (TB) during air travel. This is known to be time consuming and difficult, and increasingly so with higher numbers of flights and passengers to and from countries with high TB endemicity each year.


OBJECTIVES
This paper systematically reviews the literature on contact tracing investigations following a plane exposure to active pulmonary TB. Evidence for in-flight transmission was assessed by reviewing the positive results of contacts without prior risk factors for latent TB.


DATA SOURCES & ELIGIBILITY
A search of Medline, EMBASE, BIOSIS, Cochrane Library and Database of Systematic Reviews was carried out, with no restrictions on study design, index case characteristics, duration of flight or publication date.


RESULTS
Twenty-two papers were included, with a total of 469 index cases and 15 889 contacts. Only 26.4% of all contacts identified completed screening following exposure. The yield of either a single positive tuberculin skin test (TST) or a TST conversion attributable to in-flight transmission is between 0.19% (95%CI 0.13-0.27) and 0.74% (95%CI 0.61-0.88) of all contacts identified (0.00%, 95%CI 0.00-0.00 and 0.13%, 95%CI 0.00-0.61 in random effects meta-analysis).


LIMITATIONS
The main limitation is heterogeneity of reporting.


CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS
The evidence behind the criteria for initiating investigations is weak and it has been widely demonstrated that active screening of contacts is labour intensive and unlikely to be effective. Based on our findings, formal comprehensive contact tracing may be of limited utility following a plane exposure.