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JAMA Patient Page
February 26, 2019


JAMA. 2019;321(8):812. doi:10.1001/jama.2019.0697

Leptospirosis is an infectious disease spread by contaminated water.

Leptospirosis is an infection caused by a group of bacteria called Leptospira. It is often mild but can be fatal. It is a zoonotic infection, which means it spreads between animals and people. Many mammals can be reservoirs for leptospirosis, but rats are the most common source of human infection.

Leptospirosis causes disease in humans around the world, particularly in warmer climates and developing countries with poor housing and sanitation, but also in developed countries among outdoor recreation enthusiasts, after extreme weather events, and in certain occupations.

Past outbreaks have been associated with flooding in the Philippines, poor housing in the Bronx (New York), whitewater rafting in Costa Rica, and triathlons in the American Midwest and Europe. Recent outbreaks have occurred in Israel during the summer of 2018 and in Puerto Rico following Hurricane Maria in 2017.


Leptospirosis is one of many infections that can be transmitted by contaminated fresh water; Leptospira species cannot survive in salt water. Leptospira species are excreted in the urine of infected animals. Humans become infected when they come into contact with an infected animal’s urine or with water or mud that has been contaminated by an infected animal’s urine. The infection is acquired when the infected urine or contaminated water comes into contact with broken skin or the lining of the mouth, nose, or eyes.


The initial symptoms of leptospirosis appear an average of 10 days after exposure and are flu-like: fever, chills, headache, nausea, vomiting, cough, and diarrhea. Patients may also have red eyes (conjunctival suffusion). Many patients have a mild illness or no symptoms at all, but about 10% become severely ill. These patients may have jaundice (yellow eyes or skin) due to liver dysfunction and have significant bleeding. They may require dialysis for kidney failure or a ventilator for respiratory failure. The most severe form of leptospirosis is called Weil disease.

Diagnosis and Treatment

Leptospirosis is most often diagnosed by detecting antibodies in the blood. It can be treated with penicillins, tetracyclines, or azithromycin. Mild cases may not require antibiotics. Severe cases require supportive care in the intensive care unit as well as antibiotics.

Who Is at Risk of Acquiring Leptospirosis?

  • People who live in poor housing and with poor sanitation

  • People who wade through floodwater

  • People who swim in lakes or rivers

  • Kayakers, whitewater rafters, triathletes, and adventure racers

  • Hikers and campers

  • People in occupations such as veterinary medicine, agriculture, mining, plumbing, and garbage collection

  • International travelers


  • Avoid water or mud that may be contaminated with animal urine; in addition to rats, potential sources include a wide range of wild and domesticated animals.

  • Look for posted signs when participating in water sports.

  • Avoid swallowing water when swimming in lakes or rivers.

  • Wait until cuts and scrapes heal or cover them with bandages before submerging in possibly contaminated water.

  • Wash cuts and scrapes and shower after possible exposure.

  • Avoid wading in floodwater.

  • Wear protective shoes and clothing.

  • Reduce rodent populations whenever possible.

  • There is no widely available vaccine for humans.

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Article Information

Source: Haake DA, Levett PN. Leptospirosis in humans. Curr Top Microbiol Immunol. 2015;387:65-97. doi:10.1007/978-3-662-45059-8_5