Doctors have recently started to study the causes of a Febrile seizures are due to fevers,[5] usually those greater than 38 °C (100.4 °F).[7] The cause of the fevers is often a viral illness.[1] The likelihood of a febrile seizure is related to how high the temperature reaches.[1] Some feel that the rate of increase is not important[1] while others feel the rate of increase is a risk factor.[8] This latter position has not been proven.[8]