What Will It Take to Respond to the Threat of Zika?

The Zika virus outbreak, initially regional, is spreading through the Americas, and it does not respect country borders. The virus circulating in Brazil came from French Polynesia. However, the new virus has undergone many changes. The most concerning is its ability to damage the host nervous system. Many other flaviviruses circulate in Brazil, such as dengue, West Nile, and Japanese encephalitis viruses. Occasionally, they cause neuronal damage. Zika, however, seems to have a soft spot for neural tissues. As such, it has been linked to Guillain-Barre syndrome, encephalitis, and myelopathy in infected adults. Recent data suggest that the Brazilian strain can be transmitted vertically through the placenta, and that the virus replicates in cells of the nervous system. The viral damagemay explain the abundance of malformations in newborns from infected mothers, in particular the high incidence of microcephaly that has become a hallmark of the current outbreak. Adults seem to recover from the infection, although symptoms may reemerge a month later and the virus can remain detectable in body fluids many weeks after the acute infection. This could indicate either reinfection or viral reactivation due to incomplete immunological control of the virus. As the burden of Zika in Brazil increases, scientists have doubled their effort to catch up with the virus. We have learned a great deal, but continuous investment in research is critical if we are to understand the disease and control this uninvited guest.