Quite true, as there appear to be issues found in adult brains that have been infected. I do not agree with their analysis, but am willing to consider their position, since much is being learned each day of investigation.
Due to Virus simple construct of RNA (not DNA) the viri are subject to environmental influences, and in their natural state, viri will readily mutate.
The Brazilian agricultural environment was using a specific insecticide to kill mosquitoes; the adjoining Columbia did not use this specific insecticide.
I personally believe that the Brazilian Zika is a mutated variety which causes microcephally; whereas the Columbian Zika had a statistically insignificant occurrence of microcephally.
This is what leads me to believe that it is only the Brazilian variety, impacted by environmental chemicals/insecticides that has mutated,
and now has a certain impact on the infected human population.
For further information , see:
http://medicalxpress.com/news/2016-08-zika-infection-affect-adult-brain.html
where it states :
" ..new research in mice from scientists at The Rockefeller University and La Jolla Institute for Allergy and Immunology suggests that certain adult brain cells may be vulnerable to infection as well. Among these are populations of cells that serve to replace lost or damaged neurons throughout adulthood, and are also thought to be critical to learning and memory."
"This is the first study looking at the effect of Zika infection on the adult brain," says Joseph Gleeson, adjunct professor at Rockefeller, head of the Laboratory of Pediatric Brain Disease, and Howard Hughes Medical Institute investigator. "Based on our findings, getting infected with Zika as an adult may not be as innocuous as people think."
But those infected with ZIKA, in any of the Caribbean islands, give birth to microcephalic babies too.