Fever

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 do
• Short of Breath  —  oxygen saturation ≤90%, breathing 28 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 the spots don’t briefly lose color / turn white when 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)

Covid-19 — Everyone with a fever gets a Covid test. We can’t say “just a virus” otherwise

• 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.