Via the PLOS Speaking of Medicine blog, an important post: Could Yellow Fever Return to the United States? Excerpt (but read the whole post, which has a lot of links):
Today, the world’s yellow fever-endemic areas are restricted to Sub-Saharan Africa (figure image) and tropical regions of South America, but there are a few red flags suggesting the possibility that the “yellow jack” (a historical term used to once describe yellow fever) could return to the US. The Ae. aegypti mosquito can now be found in many areas of the southern United States. This is an area where US poverty rates are at their highest, along with its fellow travelers poor urban housing and neglected foci of standing water.
The area has also experienced unusually warm winters and springs over the past few years. Indeed, dengue fever, another arbovirus infection transmitted by Ae. aegypti mosquitoes, was recently shown to have emerged in Houston, Texas in 2003. Although Max Theiler received the Nobel Prize for developing the yellow fever vaccine in 1951, vaccination rates in the US are practically non-existent except among travelers to endemic areas.
There are several examples of US vulnerability to yellow fever, including our home city of Houston, which has recently emerged as a true gateway city and globalization hub. For instance, today, Houston hosts the world’s largest number of Nigerians expats (who provide important and skilled expertise for our city’s oil and energy industry), and there are direct flights to and from Lagos, the largest Nigerian city.
A recent study from the Division of Global Migration and Quarantine of the CDC (Centers for Disease Control and Prevention) found that US travelers to Nigeria are especially likely to decline vaccination, despite the fact that its urban areas are at especially high risk for yellow fever outbreaks.
The culmination of travelers returning to Houston from endemic areas, subtropical climate, high prevalence of Ae. aegypti mosquitoes, and areas of dense housing overlapped with poverty place Houston at risk for yellow fever emergence.