Zika virus is a mosquito-borne Flavivirus
related to dengue that is
rapidly spreading through the
Americas. This outbreak is occurring
in dengue-endemic areas
where the population has acquired
antibodies to dengue. Recent studies
reveal that preexisting dengue
antibodies may have opposite
effects on Zika infection, transmission,
and clinical outcome. Discerning
these effects is critical to
a better understanding of Zika
pathogenesis and the prevention
of future outbreaks.