Fever is defined as a temporary increase in body temperature. It is one of the most common reasons parents seek medical care for their children. Fever is typically defined as a rectal temperature of 100.4°F (38°C) or higher. Approximately 20-30% of pediatric outpatient visits involve fever as a primary complaint. Fever is significant because it often indicates an underlying infection or illness, and understanding its cause is crucial for proper management and treatment.
What is the pathogenesis of fever?
Fever is the body’s response to infection or inflammation. It is controlled by the hypothalamus, which regulates body temperature. When the body detects the presence of infectious agents such as bacteria or viruses, immune cells release pyrogens. These pyrogens act on the hypothalamus, causing it to raise the body’s set point temperature. This increases body temperature through mechanisms like shivering to generate heat and vasoconstriction to reduce heat loss.
What is the difference between fever and hyperthermia?
Fever and hyperthermia both involve elevated body temperatures, but they differ in their mechanisms and implications. Fever is a regulated increase in body temperature set by the hypothalamus in response to pyrogens. It is a controlled physiological response to infection. Hyperthermia, on the other hand, occurs when the body produces or absorbs more heat than it can dissipate. The hypothalamus does not regulate it, and it can result from external factors such as excessive heat exposure or certain medications. Hyperthermia can be dangerous and requires immediate medical intervention, whereas fever is generally a part of the body’s defense mechanism against infection.
Is the number important?
Yes, the number is important. A low fever is typically defined as a body temperature between 100.4°F (38°C) and 102.2°F (39°C). This fever range is usually not harmful and can help the body fight infections. A high fever is defined as a body temperature above 102.2°F (39°C). High fevers can be more concerning as they may indicate a more serious infection or condition. In children, a very high fever or a fever lasting more than a few days warrants medical attention to determine the underlying cause and appropriate treatment.
What is the most common cause of fever in children?
Viral infections
The most common cause of fever in children is viral infections. These infections can affect various body parts, including the respiratory system, gastrointestinal tract, etc. Common viruses include the influenza virus, respiratory syncytial virus (RSV), and adenovirus. Viral infections typically present with symptoms such as cough, runny nose, sore throat, vomiting, diarrhea, and body aches. They are more prevalent in children aged 6 months to 5 years due to their developing immune systems. Diagnosis is often clinical, based on symptoms, but may include tests like rapid influenza diagnostic tests or RSV tests. Treatment usually involves supportive care, including hydration, rest, and antipyretics like acetaminophen or ibuprofen.
Other common medical conditions associated with fever in children
Gastroenteritis
Gastroenteritis, an infection of the gastrointestinal tract, is common in young children. Symptoms include vomiting, diarrhea, and abdominal cramps. Diagnosis is based on clinical presentation and stool tests. Treatment includes hydration and supportive care.
Otitis media (ear infection)
Otitis media is an infection of the middle ear, commonly affecting children aged 6 months to 3 years. Symptoms include ear pain, irritability, and hearing loss. Diagnosis is made through otoscopy, revealing a bulging tympanic membrane. Treatment includes antibiotics and pain management.
Urinary tract infections
Urinary tract infections (UTIs) are bacterial infections of the urinary tract, common in infants and young children. Symptoms include painful urination, frequent urination, and abdominal pain. Positive urine cultures confirm the diagnosis, and treatment involves antibiotics.
Pharyngitis (throat infection)
Pharyngitis, or throat infection, often affects school-aged children. Symptoms include sore throat and difficulty swallowing. Red, swollen tonsils and positive strep tests are diagnostic clues. Treatment involves antibiotics for bacterial causes.
Roseola
Roseola, caused by human herpesvirus 6, typically affects infants and toddlers. Symptoms include a high fever followed by a rash. The rash appears as the fever subsides. Treatment is supportive.
Chickenpox
Chickenpox, caused by the varicella-zoster virus, primarily affects children under 12. Symptoms include fever and an itchy rash with fluid-filled blisters. Diagnosis is clinical. Treatment involves antiviral medications and supportive care.
Recent vaccination
Fever can occur as a reaction to recent vaccinations. It is most common in infants and young children. Symptoms typically include mild fever and soreness at the injection site. Diagnostic clues include the timing of the fever in relation to the vaccination. Treatment usually involves supportive care and medications to reduce fever and discomfort.
Less common but important medical conditions associated with fever in children
Pneumonia
Pneumonia is an infection of the lungs that can affect all ages but is more severe in infants. Symptoms include cough, difficulty breathing, and chest pain. Diagnosis is confirmed with abnormal chest X-rays. Treatment involves antibiotics for bacterial pneumonia and supportive care for viral pneumonia.
Meningitis
Meningitis is the inflammation of the protective membranes covering the brain and spinal cord. It affects people of all ages, particularly infants and adolescents. Symptoms include high fever, stiff neck, severe headache, and sensitivity to light. A lumbar puncture showing elevated white blood cells in cerebrospinal fluid confirms the diagnosis. Treatment involves antibiotics for bacterial meningitis and supportive care for viral meningitis.
Rheumatic fever
Rheumatic fever is an autoimmune reaction to a Streptococcus infection that affects children aged 5 to 15. Symptoms include fever, joint pain, and heart inflammation. Diagnosis involves positive throat cultures or rapid strep tests and elevated antistreptolysin O titers. Treatment includes antibiotics and anti-inflammatory medications.
Infectious mononucleosis
Infectious mononucleosis is caused by the Epstein-Barr virus. It often affects adolescents and young adults. Symptoms include prolonged fever, sore throat, swollen lymph nodes, and fatigue. Diagnostic clues include the presence of atypical lymphocytes in blood tests and a positive monospot test. Treatment is supportive, including rest and hydration.
Medical conditions associated with prolonged (greater than 7 days) or recurrent fever in children
Malaria
Malaria is a parasitic infection transmitted by mosquitoes. It is rare in developed countries but is very common in developing parts of the world. It can also affect children who have traveled to endemic areas. Symptoms include recurrent fever, chills, and flu-like symptoms. Diagnostic clues include travel history and blood tests showing the parasite. Treatment involves antimalarial medications.
Tuberculosis
Tuberculosis, caused by Mycobacterium tuberculosis, affects all ages, with higher risk in immunocompromised children. Symptoms include prolonged fever, night sweats, weight loss, and cough. Diagnosis involves positive tuberculin skin tests and chest X-rays. Treatment is a combination of antibiotic therapy over several months.
Kawasaki disease
Kawasaki disease causes inflammation of blood vessels, primarily in children under 5. Symptoms include prolonged fever, rash, swollen hands and feet, and red eyes. Diagnosis is clinical, with echocardiograms showing coronary artery involvement. Treatment involves intravenous immunoglobulin and aspirin.
Inflammatory bowel disease (IBD)
Inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, causes chronic inflammation of the gastrointestinal tract. It can affect children and adolescents. Symptoms include prolonged fever, abdominal pain, diarrhea, and weight loss. Diagnostic clues include endoscopic findings and biopsy results. Treatment involves medications to reduce inflammation and manage symptoms.
Tick-borne diseases
Tick-borne diseases such as Lyme disease and Rocky Mountain spotted fever are transmitted by ticks. They can cause prolonged or recurrent fever, rash, and joint pain. Diagnostic clues include a history of tick exposure and serologic tests. Treatment typically involves antibiotics.
Infective endocarditis
Infective endocarditis is an infection of the inner lining of the heart, more common in children with congenital heart defects. Symptoms include prolonged fever, heart murmur, and fatigue. Positive blood cultures and echocardiograms showing vegetation on heart valves confirm the diagnosis. Treatment involves prolonged antibiotic courses and sometimes surgery.
Juvenile idiopathic arthritis
Juvenile idiopathic arthritis is an autoimmune inflammation of the joints in children under 16 years of age. Symptoms include persistent joint swelling, stiffness, and pain. Diagnosis involves elevated inflammatory markers and positive antinuclear antibody tests. Treatment includes nonsteroidal anti-inflammatory drugs, corticosteroids, and disease-modifying antirheumatic drugs.
Cyclic neutropenia
Cyclic neutropenia involves periodic decreases in neutrophils, a type of white blood cell, affecting infants and young children. Symptoms include cyclic fevers and increased susceptibility to infections. Diagnosis is through regular blood tests showing cyclical neutropenia. Treatment involves granulocyte colony-stimulating factor and antibiotics for infections.
Systemic lupus erythematosus
Systemic lupus erythematosus is an autoimmune disorder affecting multiple organ systems, typically in adolescents and young adults. Symptoms include fever, fatigue, joint pain, and rash. Diagnosis involves positive antinuclear antibody tests and elevated inflammatory markers. Treatment includes corticosteroids and immunosuppressive medications.
Brucellosis
Brucellosis is a bacterial infection transmitted from animals and is more common in rural areas. Symptoms include prolonged fever, joint pain, and fatigue. Positive blood cultures and serological tests diagnose brucellosis. Treatment involves combination antibiotic therapy.
Familial Mediterranean fever
Familial Mediterranean fever is a genetic disorder causing recurrent inflammation. It affects children and adolescents. Symptoms include recurrent fever, abdominal pain, and arthritis. Diagnosis involves genetic testing and elevated inflammatory markers during attacks. Treatment includes colchicine and supportive care.
Cat scratch disease
Cat scratch disease is a bacterial infection caused by Bartonella henselae and is transmitted through scratches or bites from infected cats. It typically affects children. Symptoms include prolonged fever, swollen lymph nodes, and a history of cat exposure. Diagnostic clues include serologic tests for Bartonella. Treatment may include antibiotics.
Cancer of the blood or immune system
Cancer, such as leukemia or lymphoma, can cause prolonged fever due to the body’s response to abnormal cells. Symptoms include prolonged fever, fatigue, weight loss, and swollen lymph nodes. Diagnostic clues include blood tests showing abnormal cells and bone marrow biopsy results. Treatment involves chemotherapy and other cancer-specific therapies.
Additional symptoms and signs that help identify a cause
- Rash is a common symptom that, along with fever, can point to specific conditions such as roseola, chickenpox, or Kawasaki disease.
- Ear pain along with fever often indicates otitis media.
- Sore throat and fever can suggest pharyngitis.
- Cough and fever can be seen in upper respiratory tract infections and lower respiratory tract infections such as pneumonia.
- Vomiting and diarrhea with fever are signs of gastroenteritis.
- Stiff neck and severe headache along with fever are concerning for meningitis.
- Joint pain and swelling with fever may point towards juvenile idiopathic arthritis or rheumatic fever.
- Prolonged night sweats with fever can be a sign of tuberculosis or cancer.
- Fatigue and heart murmur with fever could suggest infective endocarditis.
- Abdominal pain with fever can indicate conditions like gastroenteritis, appendicitis, or familial Mediterranean fever.
- Recurrent fevers without clear infectious signs could indicate cyclic neutropenia or systemic lupus erythematosus.
Advice for parents
Parents should seek medical attention for a child with a fever if the child is younger than three months old, has a fever lasting more than three days, or has a fever above 104°F (40°C). Additionally, if the child has symptoms such as a rash, difficulty breathing, persistent vomiting or diarrhea, severe headache, stiff neck, or appears unusually drowsy or irritable, they should see a doctor. Appropriate treatment for a child with a fever includes ensuring the child stays hydrated, providing fever-reducing medications like acetaminophen or ibuprofen, and keeping the child comfortable and rested. It is essential to monitor the child’s symptoms and seek medical care if there are any concerning changes.
Summary
Fever in children is a common and important clinical symptom indicating an underlying infection or illness. It is typically defined as a body temperature of 100.4°F (38°C) or higher. The most common cause is viral infections, with other significant causes including bacterial infections and inflammatory conditions. Recognizing the additional symptoms associated with fever, such as rash or sore throat, helps diagnose the underlying condition. Effective management involves hydration, fever-reducing medications, and monitoring. Parents should seek medical attention if the fever is persistent, severe, or accompanied by worrying symptoms. Understanding these factors ensures proper care and treatment for children with fever.
References
- Green, C., Krafft, H., Guyatt, G., & Martin, D. (2023). “Symptomatic fever management in children: A systematic review of national and international guidelines.” PLOS ONE. This article reviews various clinical practice guidelines for symptomatic fever management in children, highlighting inconsistencies and assessing the quality of evidence supporting these recommendations. Available from: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0235637.
- Nijman, R. G., Moll, H. A., Vergouwe, Y., & Oostenbrink, R. (2023). “Are children with prolonged fever at a higher risk for serious illness? A prospective observational study.” Archives of Disease in Childhood. This study investigates the risk of serious bacterial infections in children presenting with prolonged fever and provides insights into clinical outcomes and management strategies. Available from: https://doi.org/10.1136/archdischild-2023-325343.
- Nijman, R. G., Vergouwe, Y., & Moll, H. A. (2023). “Fever without a source in children: International comparison of guidelines.” World Journal of Pediatrics. This review compares international guidelines for managing fever without a source in children, focusing on diagnostic and therapeutic recommendations. Available from: https://link.springer.com/article/10.1007/s12519-023-00674-1.
- Mintegi, S., & Benito, J. (2023). “Evaluation and management of young febrile infants: An overview of the American Academy of Pediatrics clinical practice guideline.” Pediatrics. This article summarizes the American Academy of Pediatrics’ guidelines for managing febrile infants, emphasizing shared decision-making and evidence-based practices. Available from: https://publications.aap.org/pediatrics/article/150/1/e2021054493/183469.