My Mother Is 85 Yr Old And Recently Came Home

My mother is 85 yr old and recently came home from a trip to California . She has vomiting, diaharia, weakness, fatigue. Prior she was very active and now just not able to shake this. I think she has a viral gastrointestinal thing and have been very insistent on her staying hydrated. Could she have contracted something else and is there a best practice for her to get back on her feet?