The evaluation of yellow fever begins with a medical history and physical examination.

Physical findings in someone with yellow fever may include:

• Blood in the stools
• Eye redness
• Urine color change:
• Brown urine
• Fever
• Cardiac arrhythmia
• Jaundice
• Liver enlargement
• Nosebleed
• Rash:
• Looks like bruises or broken blood vessels in the skin

Tests are necessary to make the diagnosis of yellow fever.

Tests that may be used to evaluate yellow fever include:

• Complete blood count
• Chest x-ray:
• Often normal
• Coagulation studies
• Electrocardiogram
• Liver profile (elevated bilirubin and liver enzymes)
• Urinalysis

Tests used to detect yellow fever include:

• Antibody studies (serology)
• Fluorescent antibody tests
• Immunoassay for mosquito cell cultures
• PCR studies to detect viral antigens

Less commonly used tests that may be used to evaluate yellow fever include:

• Spinal tap
• This is the most important test to diagnose meningitis
• Encephalitis or meningitis may cause the spinal fluid to become cloudy
• The fluid can be rapidly tested for the presence of bacteria
• CT scan of the brain
• MRI scan of the brain