That "closeness" of contact is actually largely a proxy for duration of exposure is demonstrated in this study.  An un-diagnosed sputum smear-positive flight attendant was the index case.  Exposure time of crew members to this case could be determined rather unusually precisely as in-flight time was exactly known for each member of the frequently changing crew compositions.

It is noteworthy that in excess of 10 hours exposure where needed to observe and appreciable increase in the prevalence of infection above the baseline value (diamond symbol).

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