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Update: Outbreak of Acute Febrile Illness Among Athletes Participating in Eco-Challenge-Sabah 2000 --- Borneo, Malaysia, 2000

During September 7--11, 2000, CDC was notified by the Idaho Department of Health, the Los Angeles County Department of Health Services, and the GeoSentinel Global Surveillance Network of at least 20 cases of acute febrile illness in three countries; all ill patients had participated in the Eco-Challenge-Sabah 2000 multisport expedition race in Borneo, Malaysia, during August 21--September 3, 2000 (1). Participants included athletes from 29 U.S. states and 26 countries. This report updates the ongoing investigation of this outbreak through December 2, which suggests that Leptospira were the cause of illness and that water from the Segama River was the primary source of infection. Participants in adventure sports and exotic tourism should be aware of potential exposure to unusual and emerging infectious agents.

To identify cases of febrile illness occurring at the time of the race, a standardized telephone questionnaire was administered to the athletes. Of the 304 athletes who participated in the event, 158 (52%) were contacted, including 126 (90%) of the 140 U.S. athletes. A case was defined as the acute onset of fever occurring on or after August 21, and at least two of the following symptoms: chills, myalgias, headache, diarrhea, or conjunctivitis, in an Eco-Challenge athlete (2). Of the 158 respondents, 83 (52%) reported chills; 80 (51%), myalgias; 76 (48%), headache; and 58 (36%), diarrhea. Conjunctivitis, a hallmark finding in persons infected with leptospires, was reported by 36 (23%) athletes. Arthralgias (47 [30%]), dark urine (44 [28%]), and calf/leg pain (45 [28%]) also were reported among the athletes. Of the 158 athletes contacted, 109 reported illness; 68 (44%) had illness that met the case definition. The median age of case-patients was 34 years (range: 22--50 years); 73% were male. The peak onset of illness was September 4 (Figure 1). The median duration of illness was 6 days (range: 1--19 days); 25 (34%) case-patients were hospitalized.

Laboratory evidence for leptospirosis was defined as a positive result for Leptospira antibodies by Dip-S-Ticks* (PanBio INDX, Inc., Baltimore, Maryland) or by IgM enzyme-linked immunosorbent assay (ELISA) (PanBio, Brisbane, Australia), or a positive culture. Ill athletes from whom serum specimens had been drawn by their physicians were requested to submit samples (acute and convalescent) to CDC. Of the 39 specimens submitted, 32 met the case definition. Of these, 17 (54%) tested positive by both the Dip-S-Ticks assay and the IgM ELISA; three additional serum specimens tested positive by the Dip-S-Ticks assay, but negative by IgM ELISA. Specimens from the seven participants who did not meet the case definition tested negative by both assays. Acute serum specimens were collected for culture innoculation in two athletes; one of these yielded a culture-grown isolate, and the other culture was negative at 6 weeks postinnoculation. Identification of the culture-confirmed isolate is pending. To identify other causes for febrile illnesses, testing for alternative organisms was conducted on a limited number of submitted samples positive for leptospirosis; four of four samples tested negative for dengue and for Orientia tsutsugamushi, both of which cause illness clinically similar to leptospirosis. Further testing of other samples for these pathogens is pending.

To identify potential exposure risks, information was gathered about participation in various portions of the race. Significant risk factors on univariate analysis included kayaking (risk ratio [RR]=3.0; 95% confidence interval [CI]=1.1--8.3); swimming in the . Segama River (RR=2.3; 95% CI=1.4--3.8); spelunking (RR= 2.2; 95% CI=1.1--4.2); and swallowing water from the Segama River (RR=2.0; 95% CI=1.2--3.2). When subjected to stepwise logistic regression, only participating in the river swim was significantly associated with illness. Attributable risk for swimming in the river was 38%.

On September 13, on the basis of epidemiologic evidence and the initial screening Dip-S-Ticks assay results, CDC issued an advisory about the probable leptospirosis outbreak associated with the Eco-Challenge event (1). In addition, CDC made recommendations about the treatment of leptospirosis. The Eco-Challenge organization also attempted to contact members of the race support staff and race volunteers to inform them about potential illness among these persons.

Reported by: C Hahn, MD, Idaho State Dept of Public Health. L Mascola, MD, Los Angeles County Dept of Health Svcs; R Cader, MD, D Haake, MD, Los Angeles County Veterans Affairs Medical Center, Los Angeles; D Vugia, MD, California Dept of Health Svcs. C Easman, MD, Hospital for Tropical Diseases, London, United Kingdom. J Keystone, MD, Toronto Hospital Tropical Disease Unit, Toronto, Ontario, Canada. B Connor, MD, Travelers Health Svcs, Cornell Univ, Ithaca, New York. GeoSentinel Global Surveillance Network of the International Society of Travel Medicine. Council of State and Territorial Epidemiologists. J Purdue, K Hendricks, MD, Texas Dept of Public Health. J Pape, MD, Colorado Dept of Public Health. L McFarland, MD, Louisiana Dept of Public Health. World Health Organization, Geneva, Switzerland. M Eyeson-Annan, Communicable Disease and Environmental Health, Australia. P Buck, Health Canada; H Artsob, Canadian Science Centre for Human and Animal Health, Ottawa, Ontario. M Evans, MD, R Salmon, MD, PHLS Communicable Disease Surveillance Centre, Wales; B Smyth, MD, PHLS Communicable Disease Surveillance Centre, Northern Ireland; T Coleman, MD, PHLS Leptospira Reference Unit, United Kingdom. V Cardenas, MD, TEPHINET, Div of International Health; Div of Applied Public Health Training, Epidemiology Program Office; Meningitis and Special Pathogens Br, Div of Bacterial and Mycotic Diseases; Surveillance and Epidemiology Br, Div of Quarantine, National Center for Infectious Diseases; CDC Eco-Challenge Investigation Team; and EIS officers, CDC.

Editorial Note:

Among ill Eco-Challenge participants, symptomatology and exposure history and the subsequent laboratory serologic testing suggest that leptospirosis was the cause of this outbreak. Leptospira species are endemic in Malaysian Borneo but were not recognized to be causing a large burden of disease at the time of Eco-Challenge. The epidemiology of leptospirosis and the epidemiologic data gathered from this investigation suggest a point source of the outbreak. Ill athletes who did not report swimming in the Segama River probably were exposed to contaminated water during other activities. However, some ill persons may have been infected with other pathogens, and further testing is ongoing. Recent increases in the number of persons participating in adventure sports and exotic tourism have led to infection with previously "unusual" organisms (3--7). Participants in such events should be made aware of potential risks for exposure to unusual and emerging infectious agents, and their physicians should consider infection with these agents.

Leptospirosis is a zoonotic disease of worldwide distribution that causes an acute febrile illness; the incubation period is usually 5 to 14 days, but ranges from 2 to 30 days. The illness often is characterized by the abrupt onset of fever, chills, myalgias, and headache, and may include conjunctivitis, abdominal pain, vomiting, diarrhea, and skin rashes. An acute septicemic phase can be followed by a secondary phase of severe disease characterized by aseptic meningitis, jaundice, renal failure, and hemorrhage; the disease sometimes can progress rapidly to acute respiratory distress syndrome. Mild infections can be treated with oral doxycycline; more severe infections generally require intrave nous penicillin (2).

Initial screening for leptospirosis by CDC laboratories was performed using the Dip-S-Ticks assay, an enzyme-linked dot immunoassay for detecting IgM antibodies; recent evaluations carried out at CDC indicate that the Dip-S-Ticks assay appears to have significantly greater sensitivity early in infection than other available assays (CDC, unpublished data, 2000), with a sensitivity of approximately 27% at 3 days following onset of fever, increasing to 84% for specimens collected within 7--9 days, and reaching nearly 100% by 10--12 days. Accurate diagnosis of leptospirosis has been hampered by the difficulty of the serologic testing with the gold standard microscopic agglutination test. The high sensitivity and specificity of the newer rapid assays in early infection, their ease of use, and stability in field settings probably will result in earlier and more accurate diagnosis of leptospirosis.

Several studies have demonstrated the efficacy of pre-exposure chemoprophylaxis on clinical symptoms and mortality attributed to leptospirosis using oral doxycycline at 200 mg once a week (8,9). On the basis of the high attack rate and the high proportion of hospitalizations in otherwise healthy athletes, CDC recommended empiric treatment of all ill athletes with doxycycline and that asymptomatic athletes discuss postexposure prophylaxis with their health-care provider. Persons traveling to areas where leptospirosis is endemic or epidemic and who participate in high-risk exposure activities are at increased risk for leptospirosis and may benefit from pre-exposure chemoprophylaxis. CDC is collecting data to assess the benefits of pre-exposure doxycycline chemoprophylaxis.


  1. CDC. Outbreak of acute febrile illness among participants in EcoChallenge Sabah 2000---Malaysia, 2000. MMWR 2000;49:816--7.
  2. Tappero J, Ashford D, Perkins B, eds. Leptospirosis. In: Principles and practice of infectious diseases. 5th ed. New York, New York: Churchill Livingstone, 1998.
  3. CDC. Update: leptospirosis and unexplained acute febrile illness among athletes participating in triathlons---Illinois and Wisconsin, 1998. MMWR 1998;47:673--6.
  4. CDC. Outbreak of leptospirosis among white-water rafters---Costa Rica, 1996. MMWR 1997;46:577--9.
  5. Katz A, Sasaki D, Mumm A, et al. Leptospirosis on Oahu: an outbreak among military personnel associated with recreational exposure. Mil Med 1997;162:101--4.
  6. Sacks J, Ajello L, Crockett LK. An outbreak and review of cave-associated Histoplasmosis capsulati. J Med Vet Mycol 1986;24:313--25.
  7. Lyerla R, Rigau-Perez J, Vorndam A, et al. A dengue outbreak among camp participants in a Caribbean island, 1995. J Travel Medicine 2000;7:59--63.
  8. Takafuji E, Kirkpatrick J, Miller R, et al. An efficacy trial of doxycycline chemoprophylaxis against leptospirosis. JAMA 1984;310:497--500.
  9. Seghal S, Sugunan A, Murhekar M, et al. Randomized controlled trial of doxycycline prophylaxis against leptospirosis in an endemic area. Int J Antimicrob Agents 2000;13:249--55.

*Use of trade names and commercial sources is for identification only and does not imply endorsement by CDC or the U.S. Department of Health and Human Services

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