It's really important to remember that Zika is NOT some newfangled, recently evolved disease. It has been around for decades, maybe centuries, and never got much publicity because it just wasn't that serious - more the vast majority of those who caught it, it was a non-event, resolved by the body's immune system without any noticeable symptoms, for most of the rest, nothing more than a mild cold.
You are correct, the Zika virus was discovered in 1940 and the vast, vast majority of documented cases of infant microsephaly linked to Zika come from Brazil. Brazil was the first major outbreak on large scale that can link a high rate of infant birth defects to mothers infected with Zika. However, there are several known exposures to chemicals, infections with other viruses and alcohol consumption that cause microsephaly.
At this stage there is continues to be ABSOLUTELY NO PROVEN SCIENTIFIC EVIDENCE THAT THE ZIKA VIRUS ALONE CAUSES BIRTH DEFECTS... There are only theories as the studies that are taking place, unfortunately, take time. It is possible that the dangerous insecticides commonly used in populated areas of Brazil for decades and reside within the mothers of children who used to deliver perfectly normal babies are simply pushed over the edge with the introduction of the Zika virus on top of the chemicals and they deliver children with birth defects... Like layering a cake with one causal ingredient after another layer by layer until the cake falls over. It is completely reasonable to assume that Zika infected mothers in the states who have not been exposed to other viruses and chemicals will deliver perfectly healthy babies.
The above being said, when it comes to the health of an unborn child (and I used to be very staunch in my belief that Zika presents absolutely no threat), there is reason to play it safe and not travel to areas where the virus is known to be if one is pregnant, planning on conception, or willing to "take their chances" without using birth control.
Zika is going to keep working its way north into the southern US... Just like lionfish and fire ant infestations so 1/4 - 1/2 of the USA is going to have to deal with Zika in time. In time, we'll know far more about what is causing these birth defects and whether or not the Zika virus by itself presents any reason for concern.
The wife and I booked a 2-week Dive/stay package with Tres Pelicanos last night for this winter. We are not pregnant or planning on conception. We'll be bringing a few extra cans of bug spray, apply at regular intervals, and treat our trip to Coz no different than any other trip we've taken elsewhere where there has been one heck of alot worse diseases to be caught than Zika for us.