Fever
A fever is when a person's body temperature is hotter than 37.5 degrees Celsius (99.5 Fahrenheit). Normal body temperature for humans is around 36.6 to 37 degrees Celsius (98 to 98.6 F) or a bit higher after a lot of exercise. These numbers are for a temperature taken from under the tongue. Rectal temperatures will read about 0.3 C (0.55 F) higher, and armpit temperatures will read about the same amount lower.
When people are ill, their body's immune system fights the disease, and so the body temperature rises. Fever is a defensive measure of the body against the germs: the metabolism of the germs become disoriented when the body temperature rises.
About 38.9 C (102 F) degrees is called a low-grade fever, and above 39.4 C (103 F) degrees is a high-grade fever.
Children usually have a higher fever than adults; their immune system is less mature. Infants have the highest normal temperature, which decreases as people age. Some animals, especially small ones like rabbits and cats, also have a higher normal temperature than humans.
In certain cases, high-grade fever can be considered a medical emergency. This is especially the case since at or above 42 °C (107.6 F) the organs start taking damage that may not be repairable. While most fevers are caused by Infection, whether bacterial or viral, some fevers can be caused by cancers, including Leukemia,[1] Lymphoma[2], and Renal cell carcinoma.[3]
