What is a Febrile Seizure?

Questions concerning SUDC and its association with febrile seizures are common, as recent research reports a higher incidence of febrile seizures (28.8%) among children who died of SUDC than what we would expect in the general population (~3%).1 A febrile seizure is defined as a seizure or convulsion accompanied by a fever (temperature ≥ 100.4°F or 38.3°C) that mostly occur in infants and children between ages 6 months and 5 years old.2 Febrile seizures often occur in the setting of illnesses common in childhood, such as a cold, flu, or infection outside of the central nervous system. Although the presence of a fever is a common indicator of febrile seizures at the time of its occurrence, it is important to note that at times, the seizure would precede the fever by up to a few hours or the fever would be considered low-grade (between 99.5°F or 37.5°C and 100.3°F or 38.3°C).

There are certain factors that place children at a higher risk for recurrence of febrile seizures than others, these include children who:

  • Experienced their first febrile seizure before 18 months old
  • Have a family history of febrile seizures
  • Had a febrile seizure before any other symptoms of an illness
  • Had a febrile seizure in the setting of a relatively low temperature

Additionally, 40% of children who have a history of febrile seizures are likely to experience at least another one.5

Some childhood vaccinations are associated with a slight increased risk in febrile seizures in children prone to have them. However, vaccinating children at the recommended age may prevent febrile seizures through the protection of diseases that cause fevers and febrile seizures. Learn more from the CDC here and always consult with your pediatrician on the best well care for your child. 

It is also critical to also differentiate febrile seizures from epilepsy or seizure disorders. Epilepsy is a neurological condition defined by a person having two or more unprovoked seizures, meaning that they were not caused by a known or treatable medical condition, unlike febrile seizures which are provoked by a fever or an illness. However, children with a history of febrile seizure do carry a slightly higher risk of developing epilepsy, particularly those with a history of complex febrile seizures.

Medical attention by a primary care provider is recommended for any occurrence of febrile seizures in children, as it is critical for the physician to review their medical history and to perform physical exams in order to pinpoint the cause of the febrile seizure and to rule out serious medical conditions such as meningitis (infection of the membranes surrounding the brain and spinal cord). Additionally, it is also recommended that if a child experiences a complex febrile seizure, that he or she be referred to and evaluated by a pediatric neurologist who will then perform additional testing such as an EEG (electroencephalogram), blood studies, and neuroimaging. The American Academy of Pediatrics suggests against pursuing these additional studies in a child who has only experienced a simple febrile seizure, as the risks of the additional studies carry unnecessary risks that outweigh those of the simple febrile seizure itself.2

Since SUDC has been shown to be associated with febrile seizures, we include considerations about febrile seizures when caring for SUDC siblings with febrile seizures. Please refer to our “Caring for the SUDC Sibling with Febrile Seizures” guide. 


Written by:
Joyce H. Lee, MS
Medical College of Wisconsin, Class of 2024
Former Research Data Associate at the SUDC Registry and Research Collaborative (2017-2020)



  1. Crandall LG, Lee JH, Stainman R, Friedman D, Devinsky O. Potential Role of Febrile Seizures and Other Risk Factors Associated With Sudden Deaths in Children. JAMA Netw open. 2019;2(4):e192739. doi:10.1001/jamanetworkopen.2019.2739
  2. Duffner PK, Berman PH, Baumann RJ, et al. Clinical practice guideline – Neurodiagnostic evaluation of the child with a simple febrile seizure. Pediatrics. 2011;127(2):389-394. doi:10.1542/peds.2010-3318
  3. Baram TZ, Shinnar S, Glauser TA. Febrile Seizures. Vol 17. San Diego: Academic Press; 2002:S44-S52. doi:10.1177/08830738020170010601
  4. Types of Seizures | Epilepsy Foundation. https://www.epilepsy.com/learn/types-seizures. Accessed June 29, 2021.
  5. Office of Neuroscience Communications and Engagement (NINDS N. Febrile Seizures Fact Sheet | National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Febrile-Seizures-Fact-Sheet. Accessed June 27, 2021.

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