Diagnosing. Symptoms from an EBV infection can take four to six weeks to show up once a person is exposed. In general, people usually begin feeling better after a couple of weeks. However, EBV can cause some to feel tired and fatigued for up to six months. Because symptoms of EBV can mimic the common cold or flu, for those with concerns, a trip to the doctor may be necessary. Some signs of EBV or mono that a doctor can look for include an enlarged spleen, swollen liver and white patches on the tonsils. There are also blood tests that the doctor can run.