The incubation period of Leptospirosis is anything between two to 20 days (with a range of 10 days).
The time between a person’s exposure to a contaminated source and becoming sick is two days to four weeks. Illness usually begins abruptly with fever and other symptoms. Leptospirosis may occur in two phases, after the first phase, with fever, chills, headache, muscle aches, vomiting or diarrhea, the patient may recover for a time but become ill again. If a second phase occurs, it is more severe, the person may have kidney or liver failure or meningitis. The illness lasts from a few days to three weeks or longer. Without treatment, recovery may take several months.

Leptospirosis may follow a biphasic course
Septicemic phase (with a duration of 4 to 7 days): Linterrogans dissemination in blood, cerebrospinal fluid (CSF) and most tissues. Clinically, it’s characterized by extensive vasculitis.
Immune phase (with a duration of 10 to 30 days): The leptospira disappear from the blood and CSF, remaining intermittently in the urine and aqueous humor. Clinically, it’s characterized by multisystemic manifestations.

There are two types of infections which can occur:
Anicteric Leptospirosis (90% of cases)
A) Septic phase (3 to 7 days)

• Abrupt onset with high fever and chills.
• Muscle aches, commonly involving muscles of the calf.
• Headache (associated with retrobulbar pain).
• Abdominal pain.
• Nausea.
• Vomiting.
• Diarrhea.

B) Immune phase (0 to 30 days) may or may not occur

• Aseptic meningitis
  Conjunctival hemorrhage – is a very common cause of a bloody, non–painful eye. In a sub–conjunctival hemorrhage, a small blood vessel breaks in the sclera, the white of the eye. The hemorrhage looks frightening, but is not dangerous in the least. This type of condition causes no change in vision and is not associated with discharge. The redness of the hemorrhage will usually resolve over several weeks.
• Rash.
• Cough.
• Blood–stained sputum.
• Pulmonary infiltrates.
• Acalculous cholecystitis (common in children) – gall bladder wall thickening.

Icteric Leptospiroses (5 to 10% of cases)
A) Septic phase (3 to 7 days)

• Symptoms similar to anicteric form.

B) Immune phase (7 to 30)

• “Reddish” jaundice (jaundice + conjunctival + cutaneous vasculites).
• Renal failure.
• Increase serum creatinine, with normal or decreased levels of serum potassium.
• Hemorrhagic manifestations: gastrointestinal and pulmonary hemorrhage.
• Myocarditis – inflammation or degeneration of the heart muscle.
• Pulmonary involvement.
• Hepatomegaly – liver enlargement.