Leptospirosis

  • Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Editor: Mary D. Nettleman, MD, MS, MACP
    Mary D. Nettleman, MD, MS, MACP

    Mary D. Nettleman, MD, MS, MACP

    Mary D. Nettleman, MD, MS, MACP is the Chair of the Department of Medicine at Michigan State University. She is a graduate of Vanderbilt Medical School, and completed her residency in Internal Medicine and a fellowship in Infectious Diseases at Indiana University.

What causes leptospirosis?

The cause of leptospirosis is bacteria, Leptospira interrogans, a Gram-negative spirochete (spiral-shaped bacteria). The bacteria infect many types of animals (many wild animals, rodents, dogs, cats, pigs, horses, cattle, for example) that subsequently contaminate water, lakes, rivers, soil, and crops when they urinate because the bacteria are present in urine. The bacteria then infect humans when they invade through breaks in the skin or mucus membranes or when people ingest them. The bacteria multiply in the liver, kidneys, and central nervous system. Person-to-person transfer of this disease is rare.

Is leptospirosis contagious? What is the contagious period for leptospirosis?

In general, leptospirosis is considered weakly contagious. This is because, like other animals, humans can shed leptospirosis in the urine during and after illness. Consequently, individuals exposed to the urine of humans who are infected may become infected. For example, although the bacteria are not airborne and have a low risk of being in saliva, individuals handling wet bedding or blood-soaked material from an infected person can increase the chances of getting the infection. There are a few reports of transmission between sexual partners, but the incidence of this type of spread seems very low. Unfortunately, pregnant mothers who get leptospirosis can infect their fetus.

The contagious period for leptospirosis depends on how long viable organisms are shed in the urine. Most individuals will shed organisms in the urine for a few weeks but there are reports that humans can continue to shed the organisms in urine for as long as 11 months. Some experts suggest that there is risk for up to 12 months after getting the initial infection.

What is the incubation period for leptospirosis?

The incubation period for leptospirosis is approximately seven to 12 days but it may range from two to 30 days.

What are risk factors for leptospirosis?

Risk factors include occupations that expose people to farm animals, wild animals, and to contaminated water and soil (farmers, slaughterhouse workers, veterinarians, miners, military personnel, disaster workers and victims, for example). People who participate in outdoor activities such as camping or kayaking are also at higher risk for infection. Any exposure to sewage or animal waste increases risk of getting leptospirosis.

Medically Reviewed by a Doctor on 9/12/2016

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