My 30 Year Daughter Has Been Sick For A Few

My 30 year daughter has been sick for a few weeks, weight loss, tired all the time, joint aches, rash on stomach, hands swelling, fever on and off. She is a teacher and is very active, running, yoga, kick boxing etc. She had a CBC today no results in yet. What could this be ? She works with some children from Africa but they have lived in the states for several years .