Dengue May Bring Out the Worst in Zika

Brazilian soldiers last year led a battle against Zika in a door-to-door campaign about how to control mosquitoes that carry the disease.  EVARISTO SA/AFP/GETTY IMAGES

CLICK HERE - Science - Enhancement of Zika virus pathogenesis by preexisting antiflavivirus immunity

sciencemag.org - by Jon Cohen - March 30, 2017

Close relatives have complicated relationships with each other even in the viral world. A new mouse study shows that if the animals have antibodies from dengue or West Nile virus, it sets them up for more severe disease from their close cousin, Zika virus.

If such "antibody-dependent enhancement" (ADE) also takes place in people, it could have helped fuel Zika's recent explosion in Brazil, where more than 90% of people in some communities have been infected with dengue. ADE could also complicate the development of vaccines for West Nile, dengue, and Zika. And with the onset of spring reigniting local transmission of Zika last week in the continental United States—where West Nile is widespread—ADE could give epidemiologists a new window into transmission and disease patterns.

Findings in mice, of course, often only apply to mice, as the researchers, from the Icahn School of Medicine at Mount Sinai in New York City, acknowledge. But they note in their paper, published online this week in Science, that ADE is already known to worsen some dengue infections in people . . . 

 . . . Still, even the possibility that ADE might worsen Zika in humans implies to Lim and co-authors that scientists should "exert great caution" in developing flavivirus vaccines because they might set people up for enhanced disease if they later become infected by a closely related flavivirus. And it adds to the urgency of further studies of Zika, says Lim, "to see whether this actually happens in humans."

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