Yellow fever is showing up in places where nobody was told to get vaccinated, and that geographic drift is the reason a US traveler booking a South America trip this fall needs to think about the vaccine well before packing.
The World Health Organization's most recent global assessment, published in late June with data through May 26, recorded 79 human infections across six countries in the Americas so far this year, alongside multiple outbreaks in wildlife indicating active virus circulation in forested areas. Three African countries reported 16 confirmed human cases between January and May, with 32 suspected cases under investigation in five other countries.
