Children younger than three months require medical attention, as might people with serious medical problems such as a compromised immune system or people with other symptoms. Hyperthermia requires treatment.Fever is one of the most common medical signs. It is part of about 30% of healthcare visits by children and occurs in up to 75% of adults who are seriously sick. While fever evolved as a defense mechanism, treating a fever does not appear to improve or worsen outcomes. Fever is often viewed with greater concern by parents and healthcare professionals than is usually deserved, a phenomenon known as fever phobia. Associated symptoms
A fever is usually accompanied by sickness behavior, which consists of lethargy, depression, loss of appetite, sleepiness, hyperalgesia, dehydration, and the inability to concentrate. Sleeping with a fever can often cause intense or confusing nightmares, commonly called "fever dreams". Mild to severe delirium (which can also cause hallucinations) may also present itself during high fevers. Diagnosis
A range for normal temperatures has been found. Central temperatures, such as rectal temperatures, are more accurate than peripheral temperatures. Fever is generally agreed to be present if the elevated temperature is caused by a raised set point and:

Temperature in the anus (rectum/rectal) is at or over 37.5–38.3 °C (99.5–100.9 °F) An ear (tympanic) or forehead (temporal) temperature may also be used.
: 103  Hyperthermia is not to be confused with hyperpyrexia (which is a very high fever). : 102 Clinically, it is important to distinguish between fever and hyperthermia as hyperthermia may quickly lead to death and does not respond to antipyretic medications. The distinction may however be difficult to make in an emergency setting, and is often established by identifying possible causes. : 103

Types
Various patterns of measured patient temperatures have been observed, some of which may be indicative of a particular medical diagnosis:
Continuous fever, where temperature remains above normal and does not fluctuate more than 1 °C in 24 hours (e.g. in bacterial pneumonia, typhoid, infective endocarditis, tuberculosis, or typhus. Intermittent fever is present only for a certain period, later cycling back to normal (e.g., in malaria, leishmaniasis, pyemia, sepsis, or African trypanosomiasis. Remittent fever, where the temperature remains above normal throughout the day and fluctuates more than 1 °C in 24 hours (e.g., in infective endocarditis or brucellosis). Pel–Ebstein fever is a cyclic fever that is rarely seen in patients with Hodgkins lymphoma. Undulant fever, seen in brucellosis. Typhoid fever is a continuous fever showing a characteristic step-ladder pattern, a step-wise increase in temperature with a high plateau.Among the types of intermittent fever are ones specific to cases of malaria caused by different pathogens.