The symptoms of leptospirosis usually develop suddenly around 7 to 14 days after exposure to the leptospira bacteria.

However, it is possible for symptoms to develop from between 2 and 30 days after exposure.

About 90% of leptospirosis infections only cause mild symptoms, including:

• a high temperature (fever) that is usually between 38C and 40C (100.4-104-F)
• chills
• sudden headaches
• nausea and vomiting
• loss of appetite
• muscle pain, particularly affecting the muscles in the calves and lower back
• conjunctivitis (irritation and redness of the eyes)
• cough 
• a short-lived rash

These symptoms usually resolve within five to seven days. However, in about 10% of cases people go on to experience more serious symptoms.

Severe leptospirosis

Severe leptospirosis infections are sometimes called Weil's disease. The symptoms of a severe infection usually develop one to three days after the more mild symptoms have passed.

If the condition progresses to a severe infection, it may affect organs, including the brain, liver, kidneys, heart and lungs. This can lead to further symptoms, including:

• jaundice (yellowing of the skin and the whites of the eyes)
• swollen ankles, feet or hands
• chest pain
• symptoms of meningitis or encephalitis, such as headaches, vomiting and seizures
• shortness of breath
• coughing up blood

If left untreated, the infection may be life threatening, and could lead to brain damage, kidney failure, internal bleeding and loss of lung function.