What does a typical episode of leptospirosis look like?

Clinical Presentation of Leptospirosis

Leptospirosis classically follows a biphasic course: an initial bacteremic phase with flu-like symptoms lasting 4-7 days, followed 1-3 days later by an immune phase characterized by fever, severe calf myalgia, hepatorenal syndrome, and hemorrhage. 1

Incubation Period

The incubation period ranges from 7-12 days (range: 2-30 days) after exposure to contaminated water or animal urine 1.

Clinical Spectrum

Mild Disease (Most Common)

The majority of infections present with:

• Fever with shivering (present in 95% of cases)
• Diffuse myalgia, particularly severe pain in the calf muscles (characteristic feature)
• Headache (61% of cases)
• Non-specific flu-like symptoms 2

The disease varies from mild flu-like symptoms to severe illness, with most cases being self-limiting over several weeks 1, 3.

Severe Disease (Weil's Disease)

Approximately 5-10% of infected patients develop severe leptospirosis characterized by 3, 4:

Key Features:

• Jaundice (39% of cases) - this is the strongest predictor of severe disease 2
• Hemorrhagic manifestations due to capillary fragility
• Hepatorenal failure with high bilirubin and mild transaminase elevation
• Renal dysfunction (53% of cases), ranging from mild to severe requiring dialysis
• Pulmonary involvement (20-70% of cases), occasionally progressing to severe pulmonary hemorrhage syndrome with >50% mortality 3, 4

Distinctive Clinical Signs

Conjunctival suffusion is highly suggestive when present - look for redness of the conjunctiva without discharge 1, 5. This appears early and is a valuable diagnostic clue.

Additional findings include:

• Rash (18% of cases) - may be maculopapular or petechial 2
• Herpes eruption (11% of cases)
• Cardiac involvement (10% of cases) - myocarditis or pericarditis, which independently predicts severe disease 2
• Meningitis (19% of cases) or meningoencephalitis 2
• Atypical pulmonary infiltrates on chest X-ray (26% of cases) 2

Laboratory Findings

Initial investigations show non-specific abnormalities 1:

• Thrombocytopenia (<140 G/L in 65.5% of cases) - common and helpful diagnostically
• Polymorphonuclear leukocytosis
• Proteinuria and hematuria on urinalysis
• Elevated bilirubin with mild transaminase elevation (distinguishes from viral hepatitis)
• Biochemical evidence of renal failure
• Normal clotting studies despite bleeding (due to capillary fragility, not coagulopathy)
• Markedly elevated CRP 6

Prognostic Factors

Two clinical features independently predict progression to severe disease 2:

1. Clinical jaundice (p=0.005)
2. Cardiac involvement on examination or ECG (p<0.02)

These can be identified at initial presentation and should trigger intensive monitoring and early antibiotic therapy.

Common Pitfalls

• Do not rely on the "classic triad" - the combination of fever, headache, and myalgia occurs in most cases but is non-specific
• Absence of jaundice does not exclude severe disease - pulmonary hemorrhage can occur without hepatic involvement
• The biphasic pattern may not be apparent in all cases, particularly in severe disease where progression is rapid
• Conjunctival suffusion is easily missed - specifically examine for this sign as it is highly suggestive when present
• Consider leptospirosis in any febrile patient with recent freshwater exposure (swimming, kayaking, flooding) or occupational animal contact, especially during rainy seasons in endemic areas 1, 6

The clinical presentation can mimic dengue fever, influenza, viral hepatitis, or other tropical infections, making epidemiological context (water/animal exposure) critical for diagnosis 6, 3.