How can you determine whether or not someone has a vomiting bug?

I've been low-level ill today, with a slightly sore throat and feeling weak. But this evening my sister didn't eat anything, complaining that she had a headache, stomach ache + sore throat
I'm paranoid about sick :/ and was wondering if there was any way to determine whether she just has what I have, or might have a vomiting illness
Asked Nov 26, 2013

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