Normal body temperature is usually considered to be 98.6 ℉. A degree above or below this value does not necessarily mean an abnormality and may still be normal. While the causes of elevated body temperature are numerous, infections is the commonest one. Pattern of fever (continuous/intermittent, low grade/high grade) and associated symptoms often suggest the causative disorder.
- Infections: Viral, bacterial and fungal infections can all manifest as fever. Common examples include: throat infections, chest infections, UTIs, malaria, and typhoid. Associated symptoms usually point towards the underlying cause. e.g. sore throat in pharyngitis, dysuria in UTI, and cough in chest infections.
- Inflammatory disorders: Rheumatoid arthritis, Gout, SLE etc.
- Malignancy: Any tumor can cause elevated body temperature. Malignancies commonly associated with fever include lymphomas and leukemia.
- Medications: Some prescription drugs can increase core body temperature. Example include some antibiotics, and anti-epileptics etc. Aspirin overdose can cause highly elevated body temperature along with tinnitus and confusion. Body temperature is sometimes high for a variable period of time after administration of some vaccines (e.g. DPT, pneumococcus).
- Others: Heat exhaustion, sunburn, thyrotoxic crisis, poisoning.
- Fever of Unknown origin: Temperature of 101 ℉ or above for more than 3 weeks with no obvious cause after initial clinical and lab evaluation is termed as fever/pyrexia of unknown origin (PUO). Occult infections (lung abscess, pelvic abscess etc.), TB, lymphoma, rheumatic fever, malaria, and adult still disease are few of the conditions that might not be apparent after initial workup (hence PUO).