My (crazy) knee-jerk reaction was that there was a decent chance he'd been poisoned by Israel. Doesn't make much sense though. Why make it a lingering poison, instead of something to finish him off quickly? And why take the chance of having the toxin detected by French doctors? If caught, that would really shake Israels public-relations.
Besides, what's the point of killing him? Its not like Israel is 'losing' the conflict, so why bother? Doesn't seem to profit Israel that much, so I'd have to rule assasination out, as my guess.