MMWR. 1998;47:585-588. 1 figure omitted
ON JULY 14, 1997, the Wisconsin Division of Health (WDOH) was notified by the City of Madison Health Department that three athletes were hospitalized with an acute febrile illness. The illness was characterized by fever, myalgia, and headache with illness onset on July 6, 7, and 10, respectively. One of these three athletes had acute renal failure. Two of the athletes had participated in a triathlon* held in Madison, Wisconsin, on July 5 (692 registered participants) and all three had participated in a June 21 triathlon in Springfield, Illinois (961 registered participants). Eighty persons were registered for both events. Leptospirosis was suspected by WDOH staff as a likely cause of the illness and CDC was notified. Acute-phase serum specimens from two of the three hospitalized athletes obtained 4 and 8 days following onset of fever have been tested at CDC for leptospirosis using the PanBio enzyme-linked immunosorbent assay (ELISA) IgM screening test (PanBio, Brisbane, Australia)†; one specimen tested positive. This report presents preliminary findings of an ongoing investigation to identify additional cases of acute febrile illness among athletes participating in these two triathlons and to determine the cause of the illness.
To identify additional cases of febrile illness, triathlon participant lists were obtained from the race organizers; athletes from 44 states participated in at least one of the two events. A telephone survey of participants identified additional athletes with unexplained febrile illness. On July 17, CDC issued an advisory about the probable leptospirosis outbreak to increase awareness among health-care providers, athletes who participated in the Wisconsin and Illinois triathlons, and residents of the communities in which these events were held, and to request such illnesses be reported to CDC and state and local health departments.
Through July 20, a total of 639 triathlon participants from 39 states had been interviewed by telephone using a standardized questionnaire. Interviews have been completed for 588 (61%) of the Illinois participants and for 126 (18%) of the Wisconsin participants. A case was defined as onset of fever during June 21-July 20 in a triathlon participant that was associated with at least two of the following symptoms or signs: chills, headache, myalgia, diarrhea, eye pain, or red eyes. Seventy-four (12%) participants interviewed had an illness that met the case definition. The median age of these case-patients was 36 years (range: 15-80 years); 80% were male. Case-patients were similar in age and sex to athletes who were not ill. Among case-patients, symptoms and signs of illness were chills (89%), headache (77%), myalgia (73%), diarrhea (58%), eye pain (43%), and red eyes (26%). Fifty-four (73%) sought medical care; 21 (39%) of those were hospitalized. Among hospitalized patients, two had acute renal failure, two had abdominal surgery for suspected acute abdomen, and two had neurologic illnesses; one had suspected leptospirosis diagnosed.
Among the 74 case-patients, 64 (86%), four (5%), and six (8%) participated in the Illinois triathlon, the Wisconsin triathlon, or both, respectively. Signs and symptoms of illness did not differ significantly between athletes who participated exclusively in either the Illinois or Wisconsin triathlons (two-tailed Fisher exact; all p >0.10). Acute-phase serum samples obtained from an additional 16 case-patients identified as a result of the investigation have been tested at CDC for leptospirosis using Pan-Bio ELISA IgM. Specimens from two case-patients, both of whom participated in only the Illinois triathlon, tested positive. One of the 16 case-patients, who also participated in only the Illinois triathlon and whose serum specimen tested negative, had a cholecystectomy because of acute abdomen. No histopathologic evidence of cholecystitis was seen. Immunohistochemical staining of the gall bladder at CDC using rabbit polyclonal reference antiserum reactive with 16 different leptospiral strains was positive for leptospirosis.1 Leptospiral antigens were seen as intact leptospira, thread-like filaments, and granular forms.2 Paired, 2-week convalescent serum specimens are being obtained for the 18 patients (these 16 patients and the first two patients) whose acute-phase serum specimens (three positive and 15 negative) have been tested.
CDC in collaboration with state and local health departments is continuing to conduct epidemiologic, laboratory, and environmental investigations to characterize further this outbreak. The objectives of these investigations are to identify additional cases, to determine the etiology of illness among athletes who participated in triathlons in both Illinois and Wisconsin, to identify the source and mode of transmission, and to develop prevention and control measures.
Wisconsin Outbreak Investigation Team, Wisconsin Div of Health; City of Madison Health Dept. B Davis, Springfield Dept of Public Health, Springfield; Illinois Outbreak Investigation Team, Illinois Dept of Public Health. Council of State and Territorial Epidemiologists, Atlanta, Georgia. Infectious Disease Pathology Activity, Div of Viral and Rickettsial Diseases, and Meningitis and Special Pathogens Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases; and EIS officers, CDC.
The clinical signs and symptoms of illness among athletes meeting the case definition, the serologic and immunohistochemical testing, and the epidemiologic association with prolonged water exposure (1.5-mile lake swim) among these athletes suggest that leptospirosis, a water-borne disease, most likely is the cause of this outbreak. Because the signs and symptoms of leptospirosis are nonspecific, the case definition was purposefully broad and, as a result, may be detecting illness attributable to other causes. Although current epidemiologic data suggest that an environmental exposure probably occurred in the Illinois triathlon, additional laboratory and epidemiologic investigations are needed to exclude illness attributable to more than one exposure. As a precautionary measure, the city of Springfield and the Illinois Department of Public Health have issued an advisory not to swim, water-ski, or use personal watercraft at the site on the lake where the Illinois triathlon was held. Because only 18% of the Wisconsin participants had been interviewed, further interviews and laboratory evaluation of clinical specimens among athletes who participated in the Wisconsin triathlon are needed to evaluate the possibility of illness attributable to leptospirosis and to other pathogens.
Leptospirosis is a widespread zoonosis that is endemic in most temperate and tropical climates. Leptospires infect various animals that excrete the organism in their urine; the bacteria then persist in fresh water, damp soil, vegetation, and mud. Human infection occurs through exposure to water or soil contaminated by infected animal urine and has been associated with wading, swimming, and white-water rafting in contaminated lakes and rivers.1,3- 5 Leptospires may enter the body through cut or abraded skin, mucous membranes, and conjunctivae. The incubation period is a few days to 4 weeks, and illness usually begins abruptly with fever, chills, rigors, myalgia, and headache, and may include conjunctivitis, abdominal pain, vomiting, diarrhea, and meningeal symptoms.6 Muscle pain, often severe, is most notable in the calf and lumbar areas. Skin rashes may occur. Leptospirosis can be a bi-phasic disease with an acute septicemic phase and a secondary phase of severe disease characterized by jaundice, renal failure, hemorrhage, or hemodynamic collapse.7
The organism may be isolated from samples of blood and cerebrospinal fluid obtained during the first 10 days of illness, and in the urine following the first week of illness. The microagglutination test (MAT), the standard for serologic diagnosis of leptospirosis, is time-consuming and difficult to perform.8 Therefore, the Pan-Bio ELISA is being used as a screening test in this investigation; serum specimens positive by Pan-Bio ELISA are being confirmed by MAT.
Mild infections can be treated with oral doxycycline; patients requiring hospitalization should be treated with intravenous penicillin.6 Additional information is available from CDC, telephone (888) 688-2732 ( OUTBREAK), on the World-Wide Web site, http://www.cdc.gov, or through state and local health departments.
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