Alumna Emily S. Jentes, who earned her doctorate in tropical medicine in 2008, is the lead author of a paper in Lancet Infectious Diseases that describes the effort to revise the global yellow fever risk map. The informal WHO working group Jentes worked with also developed recommendations for yellow fever vaccinations, which are described in the paper.
Since the mid-20th century the global yellow fever risk map has depicted the best estimate of the virus’ distribution and has been used to guide vaccination recommendations for travelers, according to Jentes who works with the Epidemic Intelligence Service of the Centers for Disease Control and Prevention (CDC). Jentes says, “The scarcity of well-documented and consistent methods in yellow fever risk assessment and the changing global epidemiology of the disease emphasized the need to revise and
standardize the geographical risk assessment for yellow fever.”
The World Health Organization (WHO) rose to the challenge by convening a consultation in 2008 that resulted in the creation of an informal working group to systematically
assess the risk for yellow fever transmission in South America and Africa and to ensure
that risk maps and vaccination recommendations were congruent on the basis of
Meeting via teleconference, the group reviewed the yellow fever risk profile, which is based on all available studies and reports, for every country that had risk for yellow fever virus transmission, explains Jentes. Using yellow fever case data, serological evidence, vegetation zones, and elevation boundaries, an interim harmonized global risk map
was published in WHO’s 2009 International Travel and Health publication and CDC’s 2010
Health Information for International Travel, also known as the Yellow Book.
A second WHO consultation convened in 2010 that resulted in three major, modern mapping outcomes. One, the adoption of a new term: low potential for exposure, meaning potential exposure to the virus is expected in only rare circumstances; two, changing the risk map to a vaccination map; and three, endorsement of the recommendation that a transit time of 12 hours or less in an international airport be considered to pose no risk for virus transmission.
The work of the working group is never done. The epidemiology of the yellow fever virus is dynamic and subject to changes resulting from climate change and human factors, according to Jentes. The group continues to assess vaccine risks for travelers, develop guidelines for countries that want to change their risk status, and endorse efforts to strengthen disease surveillance in affected regions.