My 29 Year Old Son Returned From A Trip To

My 29 year old son returned from a trip to Santiago, Chile 2 weeks ago. The day he returned, he began experiencing the following symptoms: drenching night sweats, headache, sore throat, fever of about 100 degrees, mild runny nose and fatigue. His blood tests indicate increased white blood count, some liver abnormality and his spleen is mildly enlarged. he tested negative for flu and malaria. any ideas on a diagnosis?