Symptoms of Giardiasis typically occur 7-10 days after exposure, but can occur in as little as 3 days, or as long as 25 days. You're right Gavia, there must have been another culprit, as this occurred on day 2! I still suspect a gastrointestinal bug of some kind, though a viral is indeed possible. She could've brought it along from home or school even! Whatever it was, she dehydrated quickly, losing H2O from, ahem, everywhere possible. Hence my flippant "Unsocial" comment. I assure you I didn't respond flippantly on that holiday. The kids enjoyed everything immensely, it was the 2 parents who were concerned. I did learn to be more prepared, and stay prepared, not only with H2O (potable), but also we've improved our med kit. Thanks for your knowledgable response Gavia, I value that.