Weather and climate will obviously play a big role in this, but even in the last few years, that leading edge, the spread, has slowed a little, in part due to climatic conditions. It is possible, as some recent work coming out of Allan Carroll's lab and his group suggests, that if the densities are low enough right now along that leading edge, which they certainly are, we may be able to suppress those populations below the point where the outbreak can continue, so it may be able to be contained.
On October 4th, 2018. See this statement in context.