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Leptospirosis-Associated Hospitalizations, United States, 1998–2009 - Volume 20, Number 8—August 2014 - Emerging Infectious Disease journal - CDC

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Leptospirosis-Associated Hospitalizations, United States, 1998–2009 - Volume 20, Number 8—August 2014 - Emerging Infectious Disease journal - CDC

Volume 20, Number 8—August 2014


Leptospirosis-Associated Hospitalizations, United States, 1998–2009

Rita M. Traxler1Comments to Author , Laura S. Callinan1, Robert C. Holman, Claudia Steiner, and Marta A. Guerra
Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (R.M. Traxler, L.S. Callinan, R.C. Holman, M.A. Guerra)Agency for Healthcare Research and Quality, Rockville, Maryland, USA (C. Steiner)


A small percentage of persons with leptospirosis, a reemerging zoonosis, experience severe complications that require hospitalization. The number of leptospirosis cases in the United States is unknown. Thus, to estimate the hospitalization rate for this disease, we analyzed US hospital discharge records for 1998–2009 for the total US population by using the Nationwide Inpatient Sample. During that time, the average annual rate of leptospirosis-associated hospitalizations was 0.6 hospitalizations/1,000,000 population. Leptospirosis-associated hospitalization rates were higher for persons >20 years of age and for male patients. For leptospirosis-associated hospitalizations, the average age of patients at admission was lower, the average length of stay for patients was longer, and hospital charges were higher than those for nonleptospirosis infectious disease–associated hospitalizations. Educating clinicians on the signs and symptoms of leptospirosis may result in earlier diagnosis and treatment and, thereby, reduced disease severity and hospitalization costs.
Leptospirosis is a bacterial zoonotic infection caused by pathogenic serovars in the genus Leptospira (1). Approximately 10% of infections in humans result in clinical disease characterized by abrupt onset of fever, headache, muscle aches, and gastrointestinal involvement (2,3). Some infected persons can experience biphasic illness, in which more severe symptoms begin after a short recovery period (2,3). A total of 10%–15% of patients with clinical disease experience severe leptospirosis, characterized by multiple organ involvement (e.g., renal and liver failure, pulmonary distress and hemorrhage, cardiac arrhythmia), and a high rate of death (2,3). Severe infections comprise the majority of reported cases, but these cases underrepresent the incidence of disease (4).
Leptospirosis has historically occurred in persons who have contact with fresh water following heavy rains and in persons who work outdoors, with animals, or in wet environments contaminated with animal urine (2,3,5). The disease occurs more frequently in adult men than in children or women (4,6), and it is most prominent during warm and rainy seasons (2,3). In the United States, new groups at risk for leptospirosis have emerged, including residents in urban areas (7) and participants in freshwater sports (8,9).
In most places worldwide, leptospirosis is considered a reemerging human and animal disease (1,5). However, the disease was not considered nationally notifiable during 1995–2012, so whether human leptospirosis is reemerging in the United States is unknown (10). During those years, leptospirosis was reportable in many states; among them, California and Hawaii showed reemergence of the disease (11,12). In addition, a report describing a higher than expected death rate among leptospirosis-infected persons in Puerto Rico suggested that, on the basis of the average death rate, many more clinical cases of leptospirosis should have been reported (13). The fewer than expected number of reported cases might have resulted from underreporting or from a lack of disease recognition. The findings in those reports indicate the potential reemergence of leptospirosis as a public health problem in the United States.
To increase our knowledge of this neglected disease in the United States, we used national hospital discharge data for 1998–2009 to estimate the number of persons in the US population with symptomatic leptospirosis requiring hospitalization. We also used the discharge data to evaluate trends of leptospirosis-associated hospitalizations during the study period and to compare hospitalizations for leptospirosis with those for other infectious diseases.


We thank the states that voluntarily participate in the Healthcare Cost and Utilization Project to produce the Nationwide Inpatient Sample and Jason Mehal for his valuable assistance with the final revisions to this article.


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Suggested citation for this article: Traxler RM, Callinan LS, Holman RC, Steiner C, Guerra MA. Leptospirosis-associated hospitalizations, United States, 1998–2009. Emerg Infect Dis. 2014 Aug [date cited]. http://dx.doi.org/10.3201/eid2008.130451
DOI: 10.3201/eid2008.130450
1These authors contributed equally to this article.

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