what is the hallmark of this is a sudden on set of weakness. usually it is -- it can be a facial droop, drooping eyelids. the most common one is a suddenly weak or paralyzed arm or leg. i talked to some of the parents who have children who have gone through this. it is so sudden that parents often times ignore it. they don't think it can be real because it is not associated with an injury. that is the hallmark sign of this. >> in terms of the ability to vaccinate against this, not currently a vaccine that is given to children in the united states but one does exist around the world. >> there are other parts of the world wherentero virus is more prevvent. in southeast asia they have been using a vaccine. it is not widespread enough in the united states to recommend that. this is still relatively new.