In humans, it causes a wide range of symptoms, while some infected persons may have no symptoms at all.

Clinical signs observed with leptospirosis vary from in apparent to fatal depending on the host resistance and the serovar. Acute leptospirosis is evident initially by a fever that may persist from a few hours to several days.

Symptoms of leptospirosis include

• Anemia.
• High fever.
• Severe headache.
• Conjunctivitis, Conjunctival Suffusion
• Meningeal Irritation
• Chills.
• Muscle aches.
• Jaundice
• Vomiting.
• May include jaundice (yellow skin and eyes).
• Anuria or Oliguria and/or Proteinuria/Oedema.
• Hemorrhages, (from the intestines, Lung Bleeding is notorious in some areas).
• Cardiac Arrhythmia or failure.
• Red eyes.
• Abdominal pain.
• Diarrhea.
• Rash.

Skin rash and a history of exposure to infected animals or an environment contaminated with animal urine can be suspected as Leptospirosis and blood test can be carried out.

If the disease is not treated, the patient could develop kidney damage, meningitis (inflammation of the membrane around the brain and spinal cord), liver failure, and respiratory distress.

In rare cases, even death could occur. Many of these symptoms can be mistaken for other diseases. Leptospirosis is confirmed by laboratory testing of a blood or urine sample. People with leptospirosis are usually quite ill and are often hospitalized.