Hi Calico, being on IM EV myself I have paid particular attention to this topic, and as of this date I have not heard of a confirmed case. This is not meant to diminsh the importance of this possible medical emergency, but just to say that the only instances I've read turned out to be fears (well founded) caused by different non related circumstances.
I am responding to this for another reason as it will keep this topic bumped up a bit to give more opportunity for qualified opinion from people who are more knowledgeable. Dani