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International Travel and the Urban Spread of Yellow Fever

Is yellow fever coming to your city or area soon??  Could be! WHO just released a paper describing the problem. Recent major outbreaks in Africa and Brazil, coupled with a severe shortage of the yellow fever vaccine are setting the stage.

In 2016, 45.2 million international air travelers departed from yellow fever endemic areas of the world. Of 11.7 million travelers 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 travelers arriving from yellow fever-endemic areas and the largest populations living in cities suitable for yellow fever transmission.

An essential tool in the fight against yellow fever is a live-attenuated vaccine developed in 1937. This vaccine is vital for the prevention and control of yellow fever epidemics since no effective antiviral therapy exists. However, a substantial proportion of the world’s yellow fever vaccine stock was recently consumed in the response to epidemics in Africa and Brazil. As a stopgap measure, the World Health Organization (WHO) approved fractional dosing to extend the vaccine supply, while recognizing that the duration of immunity may be compromised. With only four WHO-qualified yellow fever vaccine manufacturers in the world, rapid replenishment of the global emergency stockpile stretches finite resources, potentially resulting in vaccine shortages for preventive campaigns. In late 2017, stocks of YF-VAX® (Sanofi Pasteur, Lyon, France) in North America were depleted because of manufacturing difficulties. Should another urban epidemic occur in the near future, vaccine demand could easily exceed the available supply.

The movement of 11 yellow fever infected Chinese workers from Angola to China in 2016 as well as the recent movement of individuals from Brazil to Europe this year (2018) have sounded alarm bells about international spread of the virus via infected travelers. The above report contains data on numbers of travelers going from yellow fever endemic areas to cities so far free of yellow fever but have yellow fever virus vectors and numbers of unvaccinated individuals traveling to yellow fever endemic areas and returning to cities at potential risk. It is clear that a policy concerning required vaccination of travelers is needed. The time for consideration of policy changes and implementation is now, not after yellow fever appears in new locations where spread could be rapid

 

http://www.who.int/bulletin/online_first/BLT.17.205658.pdf?ua=1

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