Why am I telling you this?
Because a line in time is about to be crossed.
Brazil first reported reported positive (but unconfirmed) laboratory tests for Zika virus disease on 29th April 2015. Brazil then started to report a rise in foetal anomalies (an initial 141), in the form of microcephaly on 30th October 2015. This was 184 days - or about 6 months later.
Zika virus was first confirmed in Colombia on 16th October 2015. Today, 12th of April 2016, is 179 days, or about 6 months later. Colombia is currently carrying the next biggest load of Zika virus disease cases, after Brazil.
It would be incredibly dense of me to suggest that at exactly 184 days a whole lot of babies with microcephaly and a host of brain injuries will suddenly be born. However, we are about to cross a significant line after which we may see a steady and continuous increase in birth defects, well above the expected averages, accruing in Colombia. This is no proof, but will greatly add weight to the case for Zika virus infection causing such anomalies if it happens.
|Growing Zika virus case number trends in dark blue|
From PAHO-WHO 
We also don't know how closely the first reported detections of Zika virus correlates with the first actual cases of infection in the two countries nor who fast new cases spread.
Then, there's that hint that perhaps there is as much as a 2 month delay in reporting Zika virus positives in Colombia; factor that into the timeline above.
But from here on in, watch Colombia closely.