Leptospirosis can cause very varied symptoms in humans. Some people do not present any symptoms, and in the majority of cases (90%), those who do tend to present a non-specific febrile syndrome.
In some cases, a second phase of the disease may occur. It is typically more serious, and is known as icteric leptospirosis or Weil’s disease (5-10%). In this phase, the liver, kidneys, nervous system (meningitis) or lungs may be affected. A yellowing of the skin or mucus membranes (jaundice) is very typical.
In some cases, there may be haemorrhaging or multiple organ failure, including death of the patient.
Complications occur particularly in people over 40, and are also influenced by genetic factors (both of the person and of the bacteria).