Is a Yellow Fever Outbreak on the Horizon?
Over the past three decades, three separate mosquito-borne diseases in the Western hemisphere -- dengue, chikungunya, and Zika -- grew into serious public health threats when they struck densely populated cities and spread much more rapidly than in the villages where the cases were first documented. The same mosquito, Aedes aegypti, carries all three of those viruses, and all three of the viruses eventually made it to the United States, resulting in small outbreaks. (For example, today doctors see about 30 to 40 Zika cases in pregnant women in the U.S. each week.)
In a recent commentary for the New England Journal of Medicine Dr. Anthony Fauci of the National Institutes of Health warns that the same pattern of a small outbreak followed by a more serious escalation of a virus might be emerging in the Brazilian rain forest. The outbreak in question is yellow fever -- a viral disease that can be fatal and, in some patients, causes liver damage severe enough that the skin takes on a yellow hue. Fauci's message is that doctors should be prepared for a yellow fever outbreak. There is a yellow fever vaccine that is 99 percent effective -- a weapon doctors were not able to wield against dengue, Zika, and chikungunya -- but the current global supply of the vaccine is too small to protect even Brazil's population, much less the U.S. or other nations.
"If Aedes aegypti mosquitoes start spreading yellow fever in Brazil, there's a possibility that you might have an outbreak in very populous areas," Fauci said, quoted by NPR. "Whether that's going to happen, I don't know. But if it does, we're going to get a lot of travel-related cases in the U.S., which means physicians here have to be aware of it. This is a wake-up call. If someone comes in with an illness that's compatible with the yellow fever, you might want to ask them, 'Have you traveled to this part of Brazil?'"
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