Stages of Leptospirosis
Leptospirosis classically presents as a biphasic illness with two distinct stages: an initial septicemic (bacteremic) phase lasting 4-7 days, followed by an immune phase where antibodies cause immune-mediated complications. 1, 2, 3
Stage 1: Septicemic (Bacteremic) Phase
This initial phase occurs after an incubation period of 5-14 days (typically 1-2 weeks) following exposure to contaminated water or animal urine. 1, 4
Key clinical features include:
- High fever (usually ≥39°C) - present in 89-100% of cases, though rare afebrile presentations can occur 2, 5
- Severe myalgias, especially in the calves - a characteristic finding 2, 3
- Headache - very common presenting symptom 2, 6
- Conjunctival suffusion - a highly suggestive sign when present 2, 7
- Chills and rigors 2
Duration: This phase lasts 4-7 days, during which leptospires are present in blood and cerebrospinal fluid. 2, 3
Laboratory findings during this phase:
- Blood cultures are most likely to be positive if obtained within the first 5 days 2, 7
- Leukocytosis with polymorphonuclear predominance 2
- Proteinuria and hematuria on urinalysis 1, 2
Stage 2: Immune (Leptospiruric) Phase
After the initial septicemic phase, leptospires disappear from blood and cerebrospinal fluid as circulating antibodies develop. 3
This phase is characterized by immune-mediated complications:
- Aseptic meningitis - occurs in approximately 19% of cases 7, 3
- Uveitis - immune-mediated eye inflammation 3
- Rash - can develop during this phase 3
- Resolution of fever in mild cases 3, 4
In severe cases (Weil's disease - 5-10% of infections), this phase manifests with:
- Jaundice - markedly elevated bilirubin disproportionate to mild transaminase elevation 2, 5
- Acute renal failure - rapidly progressive kidney injury 1, 2, 6
- Hemorrhagic manifestations - bleeding complications 2
- Pulmonary involvement - occurs in 20-70% of patients, ranging from cough to severe respiratory distress 7, 3
- Cardiac involvement - myocarditis or pericarditis 7
Important Clinical Considerations
The biphasic pattern is "classical" but not universal - many patients present with a continuous illness without clear separation between phases, and the mild influenza-like form may resolve within 2 weeks without progressing to severe disease. 3, 4
Critical timing for diagnosis and treatment:
- Serology is often negative in the first week, so treatment should not be delayed waiting for confirmation 7
- IgM titers of 1:80-1:160 suggest early infection, while >1:320 is diagnostic 2
- Convalescent serology (>10 days after symptom onset) may be needed for confirmation 2, 7
- Antibiotic therapy is most effective when started before day 4 of illness 7
Common diagnostic pitfall: Leptospirosis with jaundice may be misdiagnosed as viral hepatitis - the key distinguishing feature is the pattern of markedly elevated bilirubin (>580 μmol/L) with disproportionately mild liver enzyme elevation (AST <200 U/L) combined with rapidly progressive renal failure. 2, 7, 5