1. Fever = Temperature ≥100.6° F (≥38.0° C). Fever itself does no harm; it’s the disease causing the fever that may / may not be dangerous.
Covid-19 During Pandemic: Every setting has its own way to address “fever” without letting patients mingle inside, & doing a Covid test. But we can’t send a patient off for this if they might die.
1a. We send patient to E.R. by ambulance if we have concern for:
- Septic Shock — low blood pressure, very rapid pulse, clammy skin
- Meningitis — fever + severe headache & stiff neck, or simply confused
- Cyanosis — fingers look bluish; worse if lips or face
- Short of Breath — oxygen saturation ≤90%, breathing 30 times / min., respiratory retractions (skin sucks in with each breath: over collarbones, bottom of trachea, or between ribs)
1b. If none-of-above, but patient looks / feels very ill, we give high-dose acetaminophen (Tylenol®): 1300 mg for adults, 10 mg/lb. for children. If 45 min. later, maybe fever declines but patient looks / feels the same, we send to E.R. Most patients look & feel lots better, helping our diagnosis.
2. Fever for 3 Days or Less (and patient looks OK in general) —
2a. If localizing symptom (e.g. sore throat, ear pain, kidney pain, etc.), infection there is the likely cause. We examine it / do standard tests (e.g. urinalysis for kidney pain, etc.).
2b. If there are no specific symptoms except feeling lousy, generalized achiness, maybe a headache (especially when the fever goes up), we diagnose “Influenza” / “Virus“, unless there’s reason to wonder about uncommon, often life-threatening, illnesses:
- Malaria — foreign travel in rural tropics during the last 40 days
- Rocky Mountain Spotted Fever — fever + headache, April to Sept., in southeastern US
- Meningococcemia — new spotty rash, esp. if don’t briefly lose color if pressed upon (petechiae)
- Endocarditis — injects drugs, artificial or abnormal heart valve, history of Endocarditis
- Measles, Mumps, Chickenpox — foreign travel; recent outbreak / exposure (not life-threatening; and are nowadays rare)
- Diabetic Ketoacidosis — very thirsty; drinking & urinating lots; deep rapid breathing beyond what’s expected with fever (diagnosed by simple urine test)
- AIDS — known HIV+ and not on medicine; OR risk factors without recent HIV test
- Stevens-Johnson / Toxic Epidermal Necrolysis / Toxic Shock — skin pain, muscle pain stronger than common viral aches; scattered blisters or “sunburn,” esp. if inside mouth / eyes / vagina
- Acute (Primary) HIV — if risk for having been infected in the past month (not life-threatening)
- Peritonitis — fever plus new abdominal pain that’s getting worse
- Persons with weak immune systems — elderly, alcoholics, serious chronic illnesses, etc.
For the above possibilities, we do the tests necessary (see links to the diseases)
- If negative, but other symptoms like body aches → isolate and repeat test in 2 days
3. Fever ≥4 Days (without starting to feel any better at all) — we order tests
- Covid test — if not yet done, or if negative during first few days of fever
- Urinalysis — for Kidney Infection
- Chest X-ray — for Pneumonia
- Complete Blood Count — for clues to various infections (even Leukemia)
- Liver Function Tests — for Mononucleosis & Hepatitis
- HIV test — for HIV
- If risk for HIV in the last month: HIV Viral Load (not the usual test) — for Acute HIV
4. Fever >1-2 Weeks (very rare)
- All tests as above in #3
- Blood cultures for Endocarditis (heart infection)
- CT Scan of abdomen & pelvis (for deep abscesses, cancer)
- Think about non-infectious diseases that can cause fever (cancer, blood clots, certain inflammatory diseases like arthritis etc.)
- Consult an Infectious Disease specialist
See also Fever — Full Text for more in-depth explanations and discussions.