Table 2. International air travellers arriving in cities suitable for yellow fever transmission from areas or cities where yellow fever was endemic, 2016.

Destination country or territory,a by rankb	No. travellers arriving from yellow fever-endemic areas		Urban population of destination country, millionsc	Proof of yellow fever vaccination required upon arrival
	Departure airport within 200 km of a yellow fever-endemic area (base scenario)d	Departure airport within 200 km of a city in a yellow fever-endemic area (urban scenario)e		From yellow fever-endemic countries only	From any country
1. United Statesf	2 762 081	1 659 163	9.6	No	No
2. Mexico	1 166 021	874 820	33.5	No	No
3. United Arab Emirates	890 623	717 232	0.5	No	No
4. Peru	752 113	536 161	12.1	No	No
5. Ecuador	595 181	405 106	3.0	No	No
6. Dominican Republic	538 042	322 848	3.5	No	No
7. Brazil	481 737	311 969	44.2	Nog	Nog
8. Venezuela (Bolivarian Republic of)	461 006	376 804	7.6	Yes	No
9. China	403 683	316 588	98.7	Yes	No
10. India	385 786	345 314	235.3	Yes	No
11. Cuba	372 455	237 228	3.2	Yes	No
12. Saudi Arabia	319 711	256 316	6.5	Yes	No
13. Costa Rica	283 169	216 087	1.2	Yes	No
14. United Republic of Tanzania	268 038	247 515	7.8	Yes	No
15. Egypt	217 597	204 251	22.8	Yes	No
16. Argentina	213 665	170 456	6.3	No	No
17. Rwanda	170 040	162 831	1.3	Yes	No
18. Guatemala	115 834	94 882	2.9	Yes	No
19. El Salvador	103 943	85 577	1.1	Yes	No
20. China, Hong Kong SAR	96 258	74 284	7.3	No	No
21. Sudan	90 037	48 723	5.6	Yes	No
22. Thailand	86 481	62 266	12.7	Yes	No
23. Puerto Rico	77 282	57 657	2.8	No	No
24. Jamaica	76 848	19 822	0.6	Yes	No
25. Nicaragua	68 481	59 128	1.0	No	No
Other countriesh	665 455	531 709	211.0	NA	NA
Total	11 661 567	8 394 737	742.1	NA	NA

NA: not applicable; SAR: Special Administrative Region.

^a Destination cities in these countries and territories were ecologically suitable for yellow fever virus transmission but were not in yellow fever-endemic areas.

^b Countries and territories were ranked according to the number of travellers arriving from yellow fever-endemic areas, which was determined by examining all outbound international flights from airports within areas where the World Health Organization (WHO) recommended yellow fever vaccination and all airports within 200 km of such areas.^17–19

^c Nationally aggregated population living in yellow fever-suitable cities. In the urban scenario, there were six fewer yellow fever-suitable destination cities than in the base scenario: Satna, India (population 0.31 million); Ibb, Yemen (population 0.45 million); Al Hudaydah, Yemen (population 0.57 million); Taiz, Yemen (population 0.69 million); Aden, Yemen (population 0.88 million); and Sana’a, Yemen (population 2.7 million).

^d Our base scenario considered international travellers arriving from airports within areas where WHO recommended yellow fever vaccination and all airports within 200 km of such areas.

^e Our urban scenario considered international travellers arriving from airports within 200 km of a city (population ≥ 300 000) in an area where WHO recommended yellow fever vaccination.

^f United States’ territory included all continental states and Hawaii. Puerto Rico was not included and is listed separately. Other United States territories, such as Guam, American Samoa and the United States Virgin Islands, do not have cities with at least 300 000 residents and are thus not included.

^g We did not take into account Brazil’s temporary yellow fever vaccination requirements for incoming passengers from Angola and the Democratic Republic of the Congo during the 2016 outbreak.

^h There were 29 other countries or territories suitable for yellow fever transmission (details available from the corresponding author on request).