Symptoms of leptospirosis include fever, headache, chills, muscle aches, vomiting/diarrhea, cough, conjunctival suffusion, jaundice, and sometimes a rash. The incubation period is usually 5–14 days, with a range of 2–30 days. If not treated, the patient could develop kidney failure, meningitis, liver damage, and respiratory distress. In some cases, death occurs.
Leptospires are long, thin, motile spirochetes. They are spread in the urine of animal hosts and survive well in fresh water, wet soil, and mud in warm areas. Organisms are antigenically complex, with over 300 known pathogenic serologic variants. Specific leptospiral serovars and species can vary by geographic region. The serologic characterization of an isolate is not an absolute predictor of its species designation and cannot be definitively determined by serologic testing.
Clinical course is highly variable. Most cases involve flu-like symptoms (fever, chills, muscle aches, headaches). Other symptoms may include conjunctivitis, vomiting, diarrhea, stomach pain, jaundice, cough, and rarely, a skin rash. About 10 percent of people with leptospirosis develop severe disease, including kidney failure and/or liver damage, meningitis, difficulty breathing, and bleeding. Case fatality rate is 5 to 15% in cases with severe clinical illness.
Leptospirosis has been reinstated as a nationally notifiable condition as of January 2013. The updated 2013 leptospirosis case definition is available here. Until CDC can receive extended electronic case information on leptospirosis, please continue to send case information to CDC using the case report form.
The case report form is available in English and Spanish as a fillable PDF form that can be completed electronically or can be printed and completed by hand. Completed forms can be emailed, faxed, or mailed to CDC.
Leptospirosis Fact Sheet for Clinicians contains information about the background, transmission, clinical findings, treatment, laboratory testing, sample submission, prevention, surveillance, and reporting of leptospirosis. The fact sheet is available in English and Spanish.
Incidence and Trends
- From 2014–2018, U.S. states and territories reported about 100–200 leptospirosis cases annually to the National Notifiable Diseases Surveillance System. (To view, MMWR annual summaries [2014–2015] and annual tables [2016–onwards—select year from dropdown, top right of page]).
- About 50% of leptospirosis cases occur in Puerto Rico each year. Hawaii typically reports the second-highest number of cases annually.
- In 2017, 195 leptospirosis cases were reported, the largest annual case count reported since leptospirosis was re-instated as a nationally notifiable condition in 2013. Most of the increase was due to larger numbers of leptospirosis cases in Puerto Rico and the U.S. Virgin Islands after Hurricanes Irma and Maria struck the territories in September 2017.
- Although incidence in the continental United States is relatively low compared to other countries with more tropical and sub-tropical climates, leptospirosis is considered to be the most widespread zoonotic disease in the world. In addition, health experts believe leptospirosis is under-diagnosed and underreported—so the true number of cases is likely much higher.
- It’s estimated that more than 1 million cases occur worldwide each year, resulting in about 59,000 deaths.
Find out more about laboratory submissions by visiting Bacterial Special Pathogens Branch Laboratory Submissions.