37.8 degrees refers to a body temperature of 37.8℃, and fever refers to the condition of having an elevated temperature. A temperature of 37.8℃ is generally considered as a low-grade fever.

Under normal circumstances, measuring the temperature under the armpit, on the forehead, or in the ear, any reading between 37.3℃ and 38℃ is considered as having a fever. Fevers can be categorized as low-grade, moderate, high, or very high, with a temperature of 37.8℃ falling into the low-grade category. This could be caused by viral infections such as rhinovirus, respiratory syncytial virus, or adenovirus, which commonly affect the upper respiratory tract and lead to the common cold. It could also be a result of lowered immune system function, allowing pathogens to multiply and invade the tonsils, causing tonsillitis. Additionally, intense physical activity can increase blood flow and result in a mild fever.

When experiencing fever symptoms, it is advisable to seek medical attention promptly. A thorough examination, including blood tests, urine analysis, stool examination, pathogen identification, and culture, can help determine the specific cause of the fever and guide appropriate treatment. It is recommended to get plenty of rest, consume light meals, drink plenty of water, and use warm towels to wipe the underarms and groin area for physical cooling. When the body temperature rises to 38.5℃, it is advisable to take antipyretic medications such as ibuprofen or acetaminophen under the guidance of a doctor to help lower the temperature.