A patient has been hospitalized for the past 48 hours with a fever of unknown origin. His medical record indicates tympanic temperatures of 38.7°C (101.6°F) at 0400, 36.6°C (97.9°F) at 0800, 36.9°C (98.4°F) at 1200, 37.6°C (99.6°F) at 1600, and 38.3°C (100.9°F) at 2000. How would the nurse describe this pattern of temperature measurements?