Sorry, I was trying to be PC in my post, but by "precautions" i meant precautions to prevent unplanned pregnancy. I haven't read enough on this to really say, but it sounds like the virus doesn't really hurt a healthy adult or child. But if a mother is infected with the virus while pregnant, then the fetus can have its development severely impacted including microcephaly which is really bad. So you really have to put this risk in that context - are any of the females on the trip pregnant or in that point in time in their lives where they are having or may have children.
Mosquito repellants help but are never 100%