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Epidemiologic Notes and Reports Outbreaks of Diarrheal Illness Associated with Cyanobacteria (Blue-Green Algae)-Like Bodies -- Chicago and Nepal, 1989 and 1990

Recent reports have described the detection of cyanobacteria (blue-green algae)-like bodies (CLB) in the stools of persons with a prolonged syndrome of diarrhea, anorexia, and fatigue (1--3). In each of these reports, affected persons either were immunocompromised or had recently traveled to tropical countries. During 1989 and 1990, the first three reported outbreaks of this CLB-associated syndrome occurred in immunocompetent populations, affecting at least 150 persons. This report summarizes investigations of these outbreaks, which occurred in Chicago in 1990 and in Kathmandu, Nepal, in 1989 and 1990. Chicago, 1990

On July 9, 1990, the infectious diseases department at a hospital in Chicago was notified that several staff physicians had onset of diarrhea on July 7--8. In general, manifestations included a 1-day prodrome of malaise and low-grade fever, followed by explosive watery diarrhea, anorexia, severe abdominal cramping, nausea, and occasional vomiting. Remission of diarrhea usually occurred after 3--4 days, but was followed by a cycle of relapses and remissions lasting up to 4 weeks. During remissions, patients noted continued malaise and anorexia, sometimes accompanied by constipation.

From July 10 through August 7, stool specimens were obtained from 20 ill persons (17 house staff physicians and three other employees). Cultures were negative for Salmonella, Shigella, Campylobacter, Yersinia, and Vibrio, and ova and parasites were not detected. However, direct and acid-fast stain microscopic examination of stool specimens from nine of the house staff physicians and one of the other employees revealed the presence of CLB. By the ninth week after onset of illness, CLB were not detected in seven patients for whom follow-up stool examinations were done. An epidemiologic investigation implicated exposure to a contaminated water supply as the source of infection. Based on this finding, the hospital implemented corrective measures.

The Illinois Department of Public Health laboratory and laboratories at seven nearby hospitals conducted surveillance for CLB by performing acid-fast stains on all stool specimens submitted from August 6 through 27. CLB were detected in stool specimens from two patients not involved in the hospital outbreak. One had symptoms typical of CLB-associated illness; the other could not be located for questioning. No other clusters of CLB-associated diarrhea were identified. Kathmandu, Nepal, 1989

From May through November 1989, physicians at a clinic in Kathmandu, Nepal, that serves expatriates identified more than 50 persons with a syndrome of prolonged watery diarrhea (100%), fatigue (90%), and anorexia (86%). CLB were identified in the stool samples of all persons. Duration of illness ranged from 4 to 107 days (mean: 43 days). Of the patients subsequently available for follow-up interviews, 34 received a total of 78 courses of antibiotics, including norfloxacin, tinidazole, and quinacrine; 14 received no treatment. The mean duration of illness was similar in both groups. Patients ranged in age from 1 to 67 years. Five persons became ill within 2--11 days of arrival in Nepal. No other cases were identified until May 1990 (4).

Kathmandu, Nepal, 1990

From May 16 through October 2, 1990, CLB were identified in stool specimens obtained from 85 patients at the same clinic in Kathmandu. Of 72 patients who were interviewed, at least 95% had watery, nonbloody diarrhea. The median duration of diarrhea was 17 days, with a median of seven stools per day at the peak of illness. Diarrhea was accompanied by fatigue in 97% of the patients and anorexia in 87%; the severity of symptoms varied during the course of illness.

Analysis of samples of water from various sources, raw vegetables, and cow manure detected CLB on one head of lettuce from which a patient had eaten 2 days before onset of illness. Analysis of 184 stool samples submitted by Nepali citizens to local hospitals at the end of the outbreak period detected CLB in six (3%). Reported by: F Kocka, PhD, C Peters, E Dacumos, E Azarcon, MEd, C Kallick, MD, Chicago; C Langkop, MSPH, RJ Martin, DVM, BJ Francis, MD, State Epidemiologist, Illinois Dept of Public Health. MT Cohen, MD, J Robertson, MD, DR Shlim, MD, P Fabian, MD, R Rajah, Ciwec Clinic, Kathmandu, Nepal. Div of Immunologic, Oncologic, and Hematologic Diseases, and Enteric Diseases Br, Div of Bacterial and Mycotic Diseases, Center for Infectious Diseases; Div of Field Epidemiology, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: Cyanobacteria (blue-green algae) are a diverse collection of primitive unicellular to multicellular photosynthetic bacteria usually found in water or very moist environments (5). In environments rich in nutrients, some may grow without light (6). The CLB are so named because they possess some morphologic and reproductive characteristics similar to those of the order Chroococcales of cyanobacteria (7). However, CLB do not have all of the characteristics of any known cyanobacteria type (7).

CLB may be visualized in wet mounts by light microscopy; when fresh unpreserved stools are used, CLB appear as nonrefractile, hyaline cysts, 8--9 um in diameter (3). Intact cysts contain a greenish spherical mass 6--7 um in diameter composed of a hollow cluster of refractile, membrane-bound globules containing a clear material that resembles a lipid. In preserved stools, the contents of the cysts appear as granules of irregular shape and size. CLB are refractory to most commonly used laboratory stains. However, with the modified acid-fast stain, CLB may stain deep mottled red or pink; some resist staining and appear as glassy, membranous cysts. Under ultraviolet light, CLB autofluoresce strongly, appearing as bright blue circles.

CLB may be a new human diarrheal pathogen, capable of causing prolonged diarrheal illness in immunocompromised and immunocompetent persons. Since 1986, the organism has been identified in the stools of patients who have lived in or visited the United States, the Caribbean islands, Central and South America, Southeast Asia, and Eastern Europe (7). The CLB-associated clinical syndrome (acute onset of intermittent prolonged watery diarrhea, accompanied by anorexia) reported in these three outbreaks are similar to those described in previous case reports (1--3). The association of the outbreaks in both years with the beginning of warmer temperatures suggests a possible seasonal factor.

The precise role, if any, of CLB in the pathogenesis of diarrheal illness has not been documented. Investigations are in progress to determine the extent to which the presence of CLB in stool specimens may be associated with illness and to determine possible modes of transmission, reservoirs, and other characteristics of the organism. CLB should be considered when assessing patients with unexplained prolonged diarrheal illness. CDC's Enteric Diseases Branch, Division of Bacterial and Mycotic Diseases, Center for Infectious Diseases (telephone (404) 639-3753) is interested in receiving reports of identification of CLB in stool specimens; reports may be made through state health departments.


  1. Soave R, Dubey JP, Ramos LJ, Tummings M. A new intestinal pathogen? (Abstract). Clin Res 1986;34:533A.

  2. Hart AS, Ridinger MT, Soundarajan R, Peters CS, Swiatlo AL, Kocka FE. Novel organism associated with diarrhoea in AIDS. Lancet 1990;335:169--70.

  3. Long EG, Ebrahimzadeh A, White EH, Swisher B, Callaway CS. Alga associated with diarrhea in patients with acquired immunodeficiency syndrome and in travelers. J Clin Microbiol 1990;28:1101--4.

  4. Shlim DR, Cohen MT, Eaton M, Rajah R, Long EG, Ungar BLP. An algae-like intestinal organism associated with an outbreak of prolonged diarrhea among foreigners in Nepal. Am J Trop Med Hyg (in press).

5. Staley JT, Bryant MP, Pfennig N, Holt JG, eds. Bergey's manual of systematic bacteriology. Vol 3. Baltimore: Williams and Wilkins, 1989:1710--806. 6. Humm HJ, Wicks SR. Introduction and guide to the marine blue-green algae. 1st ed. Berkeley, California: University of California Press, 1990. 7. Long EG, White EH, Carmichael WW, et al. Morphological and staining characteristics of a Cyanobacterium-like organism associated with diarrhea. J Infect Dis (in press).

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