Hi, Fever or elevated body temperature might be caused by: A virus A bacterial infection Heat exhaustion Extreme sunburn Certain inflammatory conditions such as rheumatoid arthritis — inflammation of the lining of your joints (synovium)A malignant tumor Some medications, such as antibiotics and drugs used to treat high blood pressure or seizures Some immunizations, such as the diphtheria, tetanus and acellular pertussis (DTaP) or pneumococcal vaccine Sometimes the cause of a fever can't be identified. If you have a temperature of 101 F (38.3 C) or higher for more than three weeks and your doctor isn't able to find the cause after extensive evaluation, the diagnosis may be fever of unknown origin. Drink plenty of fluids. Fever can cause fluid loss and dehydration, so drink water, juices or broth. Rest. You need rest to recover, and activity can raise your body temperature. Stay cool. Dress in light clothing, keep the room temperature cool and sleep with only a sheet or light blanket. Consult Physician...