Frequency Of Unexplained Fevers

What Causes Unexplained Fever?

Unexplained fever can have various causes, ranging in severity from 'minor' to 'generally fatal'.  Finding the true cause means ruling out or confirming each possibility – in other words, diagnosis.

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Diagnosis is usually a complex process due to the sheer number of possible causes and related symptoms.  In order to diagnose unexplained fever, we could:

  • Research the topic
  • Find a doctor with the time
  • Use a diagnostic computer system.
The process is the same, whichever method is used.

Step 1: List all Possible Causes

We begin by identifying the disease conditions which have "unexplained fever" as a symptom.  Here are eight of many possibilities (more below):
  • Lupus (SLE)
  • Crohn's Disease
  • Sarcoidosis
  • Ulcerative Colitis
  • Malaria
  • Epstein-Barr Virus
  • Rheumatoid Arthritis
  • Leukemia

Step 2: Build a Symptom Checklist

We then identify all possible symptoms and risk factors of each possible cause, and check the ones that apply:
unexplained high fevers
swollen inguinal nodes
genital sores
poor tolerance of heat
highly elevated lymphocyte count
high sensitivity to bright light
very recent visit(s) to the tropics
chronic abdominal pain
occasional 'chills'
living in the tropics
... and more than 130 others

Step 3: Rule Out or Confirm each Possible Cause

A differential diagnosis of your symptoms and risk factors finds the likely cause of unexplained fever:
Cause Probability Status
Malaria 96% Confirm
Sarcoidosis 15% Unlikely
Leukemia 12% Unlikely
Crohn's Disease 2% Ruled out
Lupus (SLE) 0% Ruled out
Ulcerative Colitis 0% Ruled out
Epstein-Barr Virus 0% Ruled out
Rheumatoid Arthritis 0% Ruled out
* This is a simple example to illustrate the process

Arriving at a Correct Diagnosis

The Analyst™ is our online diagnosis tool that learns all about you through a straightforward process of multi-level questioning, providing diagnosis at the end.

In the Metabolic Symptoms section of the questionnaire, The Analyst™ will ask the following question about frequency of unexplained fevers:
How often do you get unexplained fevers?
Possible responses:
→ Never / rarely / don't know
→ Occasionally - one or two per year
→ Frequently - several/many per year
Based on your response to this question, which may indicate either occasional unexplained fevers or frequent unexplained fevers, The Analyst™ will consider possibilities such as:

Fevers can occur due to associated bacterial, viral, or fungal infections.

Lupus, SLE (Systemic Lupus Erythematosus)

A less common but more serious constitutional feature of SLE is persistent fever.


Symptoms of malaria include fever and flu-like illness, including shaking chills, headache, muscle aches, and tiredness.

Ovarian Cysts

When an ovarian cyst becomes twisted or ruptures it can cause fever.

Ulcerative Colitis

In severe acute attacks there may be fever.

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