On July 26, 1989, 63 (42%) of 150 children attending a summer program at a day-care center in Florida experienced a gastrointestinal illness. An epidemiologic investigation by Orange County public health officials and the Florida Department of Health and Rehabilitative Services concluded that this outbreak was the result of mass sociogenic illness (MSI).

Onset of symptoms occurred within 2-40 minutes after lunch and included abdominal cramps (77%), nausea (75%), headache (51%), dizziness (30%), malaise (30%), and sore throat (11%). Vomiting was reported in 67% of children, but no distinction could be made between actual vomiting and spitting out food. The median duration of illness was 1 hour (range: 1-8 hours). Ill children ranged in age from 4 to 14 years (median: 9 years); 47 (75%) were female. Within 1-2 hours after onset, all symptomatic children were evaluated in emergency departments at local hospitals; when the children arrived at the emergency departments, most symptoms were no longer present, and all physical examination findings were normal. More than 90% of the children returned to the center on July 27, and no further episodes occurred.

A prepackaged lunch was served in one large room to the children and consisted of a ham and cheese sandwich, diced pears, chocolate milk, and apple juice. The center's staff reported that the initial case occurred in a 12-year-old girl who complained that her food tasted bad. She subsequently had nausea and vomited. As more children developed similar symptoms, some of the staff suggested to the children that the food may have been contaminated.

On July 28, 121 children at the center were interviewed in person. After the interviews, a case was defined as vomiting or nausea with abdominal cramps during or within 1 hour after the July 26 lunch. Forty-eight (47%) of 102 children who had eaten any foods served at lunch became ill, compared with one (5%) of 19 children who had eaten none of the foods (relative risk (RR)=9.1; 95% confidence interval (CI)=1.3-50.0). Among children who had eaten any of the foods, those who had eaten the sandwich were at greater risk for illness (37 (56%) of 66 compared with 11 (32%) of 34; RR=1.7; 95% CI=1.0-2.9). The attack rate did not differ by age but was greater for girls (39 (70%) of 56) than for boys (nine (20%) of 46; RR=3.6; 95% CI=1.9-6.7). Employees and teachers at the center had not eaten any of the foods and did not become ill.

Meal samples collected and tested by the Food and Drug Administration did not detect pesticide contamination, staphylococcal toxin, or Bacillus cereus; atomic absorption screening for heavy metals, zinc, and copper was also negative. Review of the food processing, storage, and refrigeration at the manufacturing plant and the day-care center did not identify deficiencies in handling or a source of contamination. The plant that had prepared the prepackaged meal had produced 3600 similar meals served in 68 different sites in central Florida on July 26. No complaints of similar symptoms were reported from the other sites. The investigation did not identify any chemical exposure, air conditioning failure, or unusually stressful situation at the center on July 26.

MSI was the suggested diagnosis by hospital physicians after children were examined on July 26. After the epidemiologic investigation, health department officials concurred with the diagnosis. Reported by: S Arcidiacono, JI Brand, MD, Orange County Health and Rehabilitative Svcs Public Health Unit; W Coppenger, PhD, Toxicology, Health and Rehabilitative Svcs Central Laboratory, RA Calder, MD, State Epidemiologist, Florida Dept of Health and Rehabilitative Svcs. Div of Environmental Hazards and Health Effects, Center for Environmental Health and Injury Control; Div of Field Svcs, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: In this outbreak, the rapid onset and disappearance of symptoms, the lack of physical findings, the preponderance of cases in females, and the absence of a laboratory-confirmed etiologic agent are consistent with MSI (1,2) (Table 1). However, three features of this outbreak distinguish it from the typical presentation of MSI: the young age of patients, the absence of documented hyperventilation, and the high prevalence of vomiting reported.

Other MSI outbreaks among children have been reported (Table 2). Risk for illness was lower among the youngest children in at least two of these outbreaks (3; CDC, unpublished data); age was not a risk factor in the Florida outbreak. In some outbreaks, the prevalence of hyperventilation, a common symptom in MSI outbreaks, has been low (7,10); in the Florida outbreak, hyperventilation symptoms could have been missed during the early phase of illness. Vomiting, although reported as the major symptom in two previous outbreaks (8,11), is not usually a principal symptom of MSI (2). Many of the children reported to have been vomiting in this outbreak may have been spitting out food because they had been told it was contaminated or because they were responding to the "line of sight" transmission that typically occurs in MSI outbreaks (1,2).

MSI outbreaks often generate substantial anxiety and concern in the community (1) and, as illustrated in this report, may present with an atypical pattern or syndrome. Early statements by local physicians and the media about the likely psychogenic origin of the illness may have contributed to the absence of recurrence in this instance (1). Timely recognition of the nature of the outbreak and prompt reassurance that the illness is self-limited and not caused by a toxic exposure are important considerations for the effective control and prevention of recurrence.

References

1. Philen RM, Kilbourne EM, McKinley TW, Parrish RG. Mass

sociogenic illness by proxy: parentally reported epidemic in an elementary school. Lancet 1989;2:1372-6.

2. Small GW, Borus JF. Outbreak of illness in a school chorus: toxic poisoning or mass hysteria? N Engl J Med 1983;308:632-5.

3. Levine RJ, Sexton DJ, Romm FJ, Wood BT. Outbreak of psychosomatic illness at a rural elementary school. Lancet 1974;2:1500-3.

4. Modan B, Swartz TA, Tirosh M, et al. The Arjenyattah epidemic: a mass phenomenon--spread and triggering factors. Lancet 1983;2:1472-4.

5. Levine RJ. Epidemic faintness and syncope in a school marching band. JAMA 1977;238:2373-6.

6. Ruiz MT, Lopez JM. Mass hysteria in a secondary school. Int J Epidemiol 1988;17:475-6.

7. Moffatt MEK. Epidemic hysteria in a Montreal train station. Pediatrics 1982;70:308-10.

8. McEvedy CP, Griffin A, Hall T. Two school epidemics. Br Med J 1966;2:1300-2.

9. Robinson P, Szewczyk M, Haddy L, Jones P, Harvey W. Outbreak of itching and rash: epidemic hysteria in an elementary school. Arch Intern Med 1984;144:1959-62. 10. Smith HCT, Eastham EJ. Outbreak of abdominal pain. Lancet 1973;2:956-8. 11. Stahl SM, Lebedun M. Mystery gas: an analysis of mass hysteria. J Health Soc Behav 1974;15:44-50.

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