Virtually all viruses are contagious ... if you are susceptible. Adults tend to carry a certain level of immunity to many viruses (and there are hundreds of them), so exposure does not necessarily mean you will catch it ... or even have the same viral response. Respiratory viruses are usually contagious a day before you know you are sick and for two days afterward.
Since I do not know the bug that has plagued your other family members, I can't address your issue specifically, but time with family is important ... and sometimes, you just have to take a chance. We all take chances going out the grocery store or restaurants, but we go anyway.
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