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Flavivirus is a group of related viruses, some of them are West Nile virus, dengue virus, yellow fever virus, Zika virus and others.
A new study that used human samples tested in mice discovered that prior infection with any flavivirus can increase the chance of Zika infection.
Exposure to one of these virus leads to more disease when exposed to related virus. Zika is spreading very fast in regions that is prone to other flaviviruses.
Human antibodies were transferred from infected human to mice to expose them to Zika virus.
The mice not giving antibodies survived Zika infection while those that received infected human antibodies did not.