Skip to main content
King County logo

Leptospirosis is a zoonotic disease caused by the bacteria Leptospira interrogans. Leptospirosis occurs worldwide, and is more common in temperate and tropical areas. Approximately 100 to 200 cases are identified annually in the United States, of which half are reported in Hawaii. Some wild and domestic animals, such as rodents, raccoons, cattle, pigs, and dogs carry the Leptospira bacteria and pass them in their urine.

Exposure occurs when water contaminated with the urine of infected animals is ingested or comes into contact with mucous membranes or breaks in the skin. People are often exposed through recreational activities such as swimming, canoeing, or participating in open water events such as triathlons or adventure travel. Leptospirosis is rarely spread from person to person.

Occupations at greater risk include farmers, rice and sugarcane field workers, miners, slaughterhouse workers, sewer workers, and veterinarians. Non-severe cases of leptospirosis are likely under-recognized and under-reported.


Resources for the general public

Resources for health care professionals


Purpose of surveillance:

  • To identify common source outbreaks
  • To identify and eliminate preventable sources of transmission

Leptospirosis case data

Local epidemiology:

The last reported human case of leptospirosis was in 2012. This probable case was likely exposed during outdoor activities in Washington state (outside King County.) The case was hospitalized but recovered.

Leptospirosis is present in wildlife in King County and cases of leptospirosis in dogs are reported each year, usually during the rainy seasons of winter and early spring.

Each year in Washington state fewer than five human cases are reported.