Leptospirosis is a geographically widespread spirochetal disease that infects humans through contact of skin or mucous membranes with contaminated urine of infected domestic and wild animals. Worldwide, rats are the most common source of human infection with a 90% carriage rate. Indirect exposure through contaminated water and soil accounts for most sporadic cases with common source outbreaks in swimmers and found in occupational groups such as rice farmers, sugarcane workers, sewer workers and military personnel. Direct exposure occurs in pet owners, veterinarians and persons working with livestock. Some individuals have minimal symptoms after infection. Leptospires can establish a symbiotic relationship with many animal hosts persisting for long periods in renal tubules. Among patients ill with leptospirosis, 90% have mild anicteric leptospirosis which is characterized by abrupt onset of fever, headache, abdominal pain, nausea, vomiting, severe myalgia and malaise. Following this initial flu-like illness, the patient may enter a phase characterized by low grade fever, throbbing headaches. The more commonly known syndrome, icteric leptospirosis (known as Weil syndrome), is a much more severe form of leptospirosis characterized by hepatic dysfunction, jaundice, impaired renal function, hemorrhage, vascular collapse and severe mental status changes with a 5-10% mortality due to hepatocellular damages.

Laboratory diagnosis of leptospirosis is most often based on serological methods. Although culture methods are understood to be of epidemiological importance, the time elapsed between the culture and the identification of the infecting organism permits only a retrospective diagnosis. Cultures from blood and cerebrospinal fluid grown on specific media during the first week of illness can be useful to confirm a diagnosis; however, it may take 6-8 weeks for organisms to grow.