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Dengue, West Nile Exposure May Worsen Zika

Experiments in mice could help explain why Zika has taken a high toll on Brazilian communities.

Emily Greenhalgh, Contributor
Sunday, May 28, 2017


Dorsal view of a Culex pipiens mosquito, a known vector for the West Nile flavivirus.

Source: CDC.


Past exposure to common viruses including dengue fever and West Nile virus could lead to more severe impacts from the Zika virus. In a new mouse study published in the journal Science on March 30, 2017, the presence of antibodies from common viruses in the flaviviridae family, which includes Zika, led to an increase in symptoms and impacts from the Zika virus itself.

Researchers from the Icahn School of Medicine at Mount Sinai in New York administered plasma containing dengue or West Nile antibodies to mice engineered to be susceptible to the Zika virus. When these mice were then infected with Zika, they suffered an increase in morbidity and mortality, including fever, as well as increased presence of the virus in their blood, spinal cords and testes.

The researchers found that the effects were different depending on the quantity of flavivirus antibodies that were administered. Low concentrations of dengue or West Nile antibodies enhanced Zika, but high concentrations of dengue antibodies protected the animals against the Zika infection.

If this “antibody-dependent enhancement” is also present in humans, it could explain Brazil’s recent problems with the Zika virus. More than 90 percent of people in some Brazilian communities have been infected with dengue.

This adds another level of complexity to efforts to develop a Zika vaccine, especially in areas where other flaviviruses are prevalent.