Abstract
ObjectiveTo examine the potential for international travel to spread yellow fever virus to cities around the world.MethodsWe obtained data on the international flight itineraries of travellers who departed yellow fever-endemic areas of the world in 2016 for cities either where yellow fever was endemic or which were suitable for viral transmission. Using a global ecological model of dengue virus transmission, we predicted the suitability of cities in non-endemic areas for yellow fever transmission. We obtained information on national entry requirements for yellow fever vaccination at travellers’ destination cities.FindingsIn 2016, 45.2 million international air travellers departed from yellow fever-endemic areas of the world. Of 11.7 million travellers with destinations in 472 cities where yellow fever was not endemic but which were suitable for virus transmission, 7.7 million (65.7%) were not required to provide proof of vaccination upon arrival. Brazil, China, India, Mexico, Peru and the United States of America had the highest volumes of travellers arriving from yellow fever-endemic areas and the largest populations living in cities suitable for yellow fever transmission.ConclusionEach year millions of travellers depart from yellow fever-endemic areas of the world for cities in non-endemic areas that appear suitable for viral transmission without having to provide proof of vaccination. Rapid global changes in human mobility and urbanization make it vital for countries to re-examine their vaccination policies and practices to prevent urban yellow fever epidemics.
Highlights
In December 2015, Angola reported its first locally acquired case of yellow fever in nearly a decade
To identify gaps in yellow fever vaccination policies around the world, we assessed the potential for the international spread of yellow fever from areas deemed by World Health Organization (WHO) to be at risk of transmission to areas where conditions are known, or predicted, to be suitable for transmission
We considered places where WHO recommended yellow fever vaccination in 2016, including recently identified parts of Brazil, to be areas where humans were at risk of local infection.[18,19,20]
Summary
In December 2015, Angola reported its first locally acquired case of yellow fever in nearly a decade. Increased air travel and globalization is making it easier for humans to transport yellow fever virus across international borders, potentially catalysing deadly urban epidemics.[3]
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