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Health Care Workers

Technical Information

Clinical Features

Symptoms include fever, headache, chills, muscle aches, vomiting, jaundice, anemia, and sometimes a rash. The incubation period is usually 7 days, with a range of 2-29 days. If not treated, the patient could develop kidney damage, meningitis, liver failure, and respiratory distress. In rare cases, death occurs.

Etiologic Agent

Leptospires are long, thin, motile spirochetes. They may be free-living or associated with animal hosts and survive well in fresh water, soil, and mud in tropical areas. Organisms are antigenically complex, with over 200 known pathogenic serologic variants. Although certain geographic regions contain specific leptospiral serovars and species, the serologic characterization of an isolate is not an absolute predictor of its species designation.


Clinical course is highly variable. The serious icteric form (Weil’s disease) is not common, but hemorrhage, hepatomegaly, pulmonary hemorrhage, ARDS, and jaundice are among the severe features. Case fatality rate is 1 to 5%.


Leptospirosis has been reinstated as a nationally notifiable disease as of January 2013. Read the updated 2013 case definition. Until CDC can receive case data via the Nationally Notifiable Disease Surveillance System, please send case notifications on the case report form [PDF – 1 MB].

Incidence and Trends

  • It is estimated that 100-200 Leptospirosis cases are identified annually in the United States. About 50% of cases occur in Hawaii.
  • The largest recorded U.S. outbreak occurred in 1998, when 775 people were exposed to the disease. Of these, 110 became infected.
  • Although incidence in the United States is relatively low, leptospirosis is considered to be the most widespread zoonotic disease in the world.
  • Significant increases in incidence have been reported from Peru and Ecuador following heavy rainfall and flooding in the spring of 1998. Thailand has also reported a rapid increase in incidence between 1995 and 2000.

Laboratory Submissions

Find out more about laboratory submissions by visiting the Bacterial Special Pathogens Branch Laboratory Submissions.