8 year old cousin vomited 1am tuesday, then was totally fine by the time she woke up in morning. im seeing her thursday for thanksgiving. not sure if it was a virus, but how can i avoid if it was, & what are the odds of getting it if it was a virus?

Too soon to tell: Contagiousness varies among different "stomach viruses" and among different people, so is not easily predictable. However, one can feel much safer if the sick person wakes up on Day 5 without any symptoms the preceding 4 days. If unlucky, one can still catch a virus and come down with the illness. Food poisoning is usually less contagious, but depends on the bacteria type.

Some basics: Most gut viruses, if that is what this is/was, are transferred through saliva during the initial phase. This is usually marked by fever, but not always. If there is no fever it is likely not very contagious, but good hand washing & limited contact would be the way to avoid it.

Hydration: Provide hydration to your cousin. Use good hand washing and sanitizer to reduce the risk of acquiring the virus.