What are the symptoms of leptospirosis?

Symptoms of Leptospirosis

Leptospirosis typically presents with sudden onset of high fever, severe myalgias (especially in the calves, thighs, and lumbar region), frontal headache, chills, and conjunctival suffusion—a highly characteristic non-purulent redness of the eyes without discharge that should immediately raise suspicion for the disease. 1, 2

Early Bacteremic Phase (Days 1–7)

The initial septicemic phase lasts 4–7 days and is characterized by: 3

• High fever (usually ≥39°C) with sudden onset 3, 4
• Severe generalized malaise and weakness 2, 4
• Intense myalgias, particularly affecting the calves, thighs, and lumbar region—this calf pain is a distinguishing feature 1, 2, 5
• Frontal headache that can be severe 1, 3
• Chills accompanying the fever 1, 5
• Conjunctival suffusion—a highly suggestive physical finding consisting of bilateral conjunctival redness without purulent discharge 1, 2, 3, 4, 5

Additional symptoms during this phase may include: 5

• Nausea and vomiting 5
• Diarrhea 5
• Cough and respiratory symptoms 3

Biphasic Illness Pattern

The illness characteristically follows a biphasic course: an initial bacteremic phase lasting 4–7 days, followed by a brief period of improvement, then a second immune phase. 2 During the immune phase, approximately 19% of patients develop aseptic meningitis. 3

Severe Disease (Weil's Disease)

In 5–10% of cases, patients progress to severe leptospirosis with: 3

• Jaundice—marked hyperbilirubinemia with only modest elevations of transaminases (distinguishing it from viral hepatitis) 1, 2, 3
• Renal failure—acute kidney injury occurs in roughly 30% of severe cases 2, 3
• Hemorrhagic manifestations—bleeding complications are common 1, 6
• Pulmonary hemorrhage syndrome—severe alveolar hemorrhage with a fatality rate >50% 6
• Hepatomegaly 2
• Signs of respiratory distress or hypoxemia 2

Laboratory Findings That Support Clinical Diagnosis

While not symptoms per se, these findings accompany the clinical presentation: 3, 4

• Proteinuria and hematuria on urinalysis 3, 4
• Leukocytosis with neutrophilia 3, 4
• Elevated erythrocyte sedimentation rate 4
• Elevated bilirubin with mild elevation of transaminases 3
• Alterations in renal function tests 3

Key Diagnostic Considerations

Most human leptospiral infections (approximately 90%) are asymptomatic or present as mild, undifferentiated febrile illnesses, making the diagnosis challenging. 5, 7 The disease is often misdiagnosed as influenza, dengue fever, aseptic meningitis, viral hepatitis, or fever of unknown origin because of its nonspecific presentation. 7, 6

Exposure history within the past 2–20 days is critical—including contact with flood water, contaminated fresh water, recreational water sports, occupational exposure to animals, or contact with rats, dogs, cattle, or other animals. 2, 3 The typical incubation period is 5–14 days. 5

Common Pitfalls to Avoid

• Do not wait for jaundice or hemorrhage to make the diagnosis—these severe manifestations are rarely useful for early diagnosis and appear late in the disease course. 4
• Do not dismiss the diagnosis in non-tropical or urban settings—leptospirosis can occur in any geographic location, including cold and semiarid climates like Wyoming. 5
• Do not confuse with viral hepatitis—the pattern of marked jaundice with minimal transaminase elevation distinguishes leptospirosis from hepatitis. 2, 3