Risk of measles transmission on aeroplanes: Australian experience 2007-2011

Objective: To quantify the risk of transmission of measles associated with infectious people who travelled on aeroplane flights to or within Australia. Design, setting and subjects: Data were obtained from state and territory health authorities on all measles notifications from January 2007 to June 2011 for people who were likely to have been infectious or infected while travelling on aeroplanes in Australia. Results: Forty-five infectious people travelled on aeroplanes. Twenty secondary infections occurred in people on seven of 49 flights (14%; 95% CI, 6%-29%), comprising 19% (95% CI, 8%-40%) of the 36 international flights and none of 13 (95% CI, 0-28%) domestic flights that carried infectious people. Secondary infections occurred in nine people who were seated within two rows of the index case and in 11 people who were seated outside of two rows. Secondary transmission was more likely to occur with younger index cases (P=0.025) and when there were multiple infectious people travelling (P = 0.018). About a third (15/49) of flight manifests were available to health authorities within 5 days of travel. Conclusion: Despite secondary measles transmission occurring on 19% of international flights carrying infectious people, risk was not clearly related to seating proximity, and contact tracing was ineffective, especially given delays in diagnosis, notification and accessing flight manifests. We recommend that direct contact tracing to identify susceptible people exposed to people infected with measles on aeroplane flights should not be undertaken routinely, and other strategies should be considered.