Epidemiology

Most commonly found in tropical climates

Etiology

Pathogen: Leptospira (especially L. interrogans sensu lato), a genus of gram-negative spirochete with hook-shaped ends
- Spirochetes cannot be visualized using Gram staining and require specialized staining methods.
Transmission
- Sources
  - Urine, blood, or tissue of an infected animal (most commonly rats)
  - Environmental contamination (e.g., water contaminated with urine of infected animals)
- Entry points: broken skin or exposed mucous membranes (e.g., conjunctiva, oral mucosa)
- Risk factors
  - Occupations that involve direct or indirect contact with animals (e.g., agricultural or sewage workers)
  - Freshwater recreational activities (e.g., canoeing, swimming, windsurfing)

Tip

钩端螺旋体病分型（肺肾脑流黄）

流感伤寒型

肺出血型，死亡率最高

黄疸出血型，最常见

肾衰型

脑膜炎型

Biphasic illness is characteristic.
Phase 1: Septicemic/Acute Phase (1 week)
- Abrupt onset of flu-like symptoms: high fever, chills, severe myalgias (classically in calves and lumbar area), headache.
- Conjunctival suffusion (redness without exudate) is a key finding.
- Photophobia, nausea, vomiting, diarrhea may occur.
Phase 2: Immune Phase
- Recurrence of fever after a brief remission.
- May lead to aseptic meningitis.
Weil’s Disease (Severe Icteric Leptospirosis)
- Severe form in ~10% of cases.
- Triad of jaundice (hepatic dysfunction), renal failure (azotemia), and hemorrhage (thrombocytopenia).
- Can progress to multi-organ failure, ARDS (pulmonary hemorrhage), and shock.