https:// www.nature.com/news/zika-and-birth-defects-what-we-know-and-what-we-don-t-1.19596
"As of 12 March, the country’s health ministry reports 6,398 ‘suspected’ cases of microcephaly and/or central nervous system malformations since November 2015; although only 2,197 have so far been investigated. Of those, 854 have been confirmed as microcephaly, and in 97 cases laboratory tests have confirmed a link with the Zika virus."
So even at the height of the Zika "epidemic," they data showed at a 95 % confidence level that between 9.2 and 13.5 percent of confirmed microphelany cases tested positive for the Zika virus.
This wasn't science. It's a scare tactic by the CDC and probably covering up for something else. Thousands of women were panicking and getting abortions. Many more people were holding off on having children. The Zika story was the perfect narrative for population control.