Table 1.

Efficiency of airport-based interventions to screen international travellers departing Guinea, Liberia, and Sierra Leone by frontier

		Exit screening	Entry screening of direct flights	Entry screening of indirect flights
Number of cities where screening would be required		3*	15†	1238
Estimated number of travellers who would be screened		144 798	144 798	362 855 926
Estimated number of low-risk‡ travellers who would be screened (%)		376 (0·1%)	376 (0·1%)	362 711 504 (99·9%)
Number of travellers needed to screen to assess one traveller with potential exposure to Ebola virus§		1	1	2512
Travel time until screening, h
	Median (IQR)	0	2·7 (2·0–6·1)	4·0 (2·0–7·6)¶
	Mean (SD)	0	3·9 (2·6)	5·8 (4·9)

Data include travellers departing Guinea, Liberia, and Sierra Leone and travellers on connecting flights departing these countries. Data are based on air traveller flows reported from Sept 1, 2013, to Dec 31, 2013.

^*Four international airports in three cities across three countries (since these countries do not have any solely domestic airport this number represents all airports in the three countries); one airport in Monrovia has since been closed.

^†16 airports in 15 cities across 15 countries.

^‡We defined low-risk travellers as any traveller with an origin outside Guinea, Liberia, or Sierra Leone, including those simply transiting through these countries.

^§We defined travellers with possible exposure to Ebola virus as individuals initiating travel from any domestic or international airport within Guinea, Liberia, and Sierra Leone. Travellers transiting through airports within Guinea, Liberia, and Sierra Leone or initiating travel from Senegal or Nigeria were not deemed to have such an exposure risk.

^¶We assumed a 1 h layover for domestic flights and a 2 h layover for international flights.