Are Aircraft Passengers More Susceptible to Colds?

An impression exists among frequent fliers that colds and flu are more prevalent after flying than from normal ground level exposures. A recent, well designed survey of adult passengers on 2/2 hour flights established that an average of 20% selfreported colds were experienced by these travellers when questioned 5 to 7 days after the flight. We have taken the details of these survey results and compared them with the relevant frequency of colds, 2.2, or 2 to 4 colds per person year, experienced by ground level adults by converting these to common units. When the scenarios of 6 days, 24 hours, or 5 hours were taken as the relevant flight exposure times to colds, passenger transmission rates for colds of 5, 23, and 113 times the normal daily ground level transmission rate were obtained. Primarily for internal verification purposes annual infection rates were also calculated by a somewhat different method to give aircraft transmission rates of 12, 60, and 350 colds/person year for the same flight exposure scenarios. Recent published tuberculosis transmission rates are also compared and found to be substantially greater for aircraft passengers than for ground level adults. This revealed an exception for cockpit crew for whom tuberculosis transmission could not be demonstrated, which we attempt to explain.