Zika virus likely circulated in Americas long before detection during 2015-16 epidemic. Analysis of the largest collection of Zika genomes to date reveals the trajectory and evolution of the virus as it spread throughout the Americas, with implications for future surveillance efforts. Ref. Source 9l.
Viruses are always changing and adopting to their environment that is the big issue with the drug companies and the possibility of developing a super bug that will be resistant to all of our antibiotics. I think the Zika virus while yes a tropical or sub tropical virus could not get a firm hold here in the states due to the hygiene here and therefore could not adopt quick enough before dying out.
Vaccines protect fetuses from Zika infection, mouse study shows. Zika virus can cause severe brain damage in people infected before birth. A new study in mice shows that females vaccinated before pregnancy and infected with Zika virus while pregnant bear pups who show no trace of the virus. The findings offer the first evidence that an effective vaccine administered prior to pregnancy can protect vulnerable fetuses from Zika infection and resulting injury. Source 9v.
Zika virus infects developing brain by first infecting cells meant to defend against it. Researchers report that the Zika virus is transmitted from mother to fetus by infected cells that, ironically, will later develop into the brain's first and primary form of defense against invasive pathogens. Source 6j.
Zika is a interesting disease. The fact that it tends to effect more of a poorer culture of people than a more modern culture shows that we have to do much more in making everyone in the world understand the importance of being clean.