Outbreak of histoplasmosis associated with the 1970 earth day activities

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  • Outbreak of Histoplasmosis Associated with the 1970 Earth Day Activities






    Atlanta, Georgia

    An outbreak of histoplasmosis occurred in early May 1970 at a junior high school in Delaware, Ohio; clinical illness occurred in 384 (40 per cent) of the students and faculty, with probably an equal number of subclinical cases. The mode of spread was airborne and was shown epidemiologically to be related to ac- tivities on Earth Day, April 22, 1970, when the courtyard in the center of the school, an old bird roost, was raked and swept. Contamination of the entire school building with courtyard air occurred via the schools forced air ventilation system with in- takes in the courtyard. Soil samples from the courtyard were positive for Histoplasma capsulatum, but random samples from other areas around the building were negative. In two persons in the building only on April 22, the typical illness developed. Features of the outbreak have important implications for clini- cians and public health officials.

    From the Viral Diseases Branch, Epidemiol- ogy Program, Center for Disease Control, Health Services and Mental Health Adminis- tration, Public Health Service, U.S. Depart- ment of Health, Education and Welfare, At- lanta, Georgia 30333. Requests for reprints should be addressed to Dr. Michael B. Gregg, Viral Diseases Branch, Epidemiology Program, Center for Disease Control, Atlan- ta, Georgia 30333. Manuscript received NO- vember 2, 1972; accepted November 9, 1972. ._.-.

    *Present address: Rheumatology Division, University of Texas Southwestern Medical School, Dallas, Texas 75235.

    tPresent address: Boston City Hospital, 818 Harrison Avenue, Boston, Massachu- setts 02118.

    Contaminated starling roosts, particularly in urban areas, are now among the major sources of epidemic histoplasmosis [l] in contrast to the chicken and pigeon roosts in rural settings implicated in earlier studies [2]. An explosive outbreak of respi- ratory illness localized at a junior high school was recently in- vestigated and found to be an epidemic of histoplasmosis relat- ed to cleaning activities in a starling and blackbird roost area. The well defined nature of the outbreak provided an unusual opportunity to study the epidemiology of the airborne route of fungus dissemination as well as the clinical and laboratory di- agnostic features of acute histoplasmosis.

    It seems somewhat paradoxic in light of the current interest in environmental contamination that as the result of a well meant attempt at cleaning up the environment, the largest number of clinical cases of histoplasmosis ever to be reported in a single epidemic occurred.


    Delaware, Ohio, a town of approximately 15,000 persons, is the county seat of Delaware County (population 45,000) and is lo- cated-in the central portion of the-state. The town has five ele- mentary schools, an intermediate school (the Willis Intermediate School, grades 6-8), a high school (Hayes High, grades g-12), a parochial school (grades l-8) and a liberal arts college (Ohio Wesleyan University) (Figure 1) .

    March 1973 The American Journal of Medicine Volume 54 333


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    Figure 1. Schools in De/a ware, Ohio.

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    Figure 2. Layout of Willis Intermediate School.

    334 March 1973 The American Journal of Medicine Volume 54

  • The Willis School is housed in two buildings, a 2 l/2 new building (circa 1933) and a 3 story old building (circa 1867), which are connected by a long first floor hall (Figure 2). The sixth grade is housed in the old building, and each stu- dent has his own individual schedule of classes. The seventh and eighth grades are housed in the new building, and these students move as a unit to various classrooms throughout this building.

    The sixth grade uses the cafeteria, auditorium and gym in the new building.

    When an alarming increase in absenteeism oc-

    curred relatively suddenly and involved only the Willis School, local and state health officials were notified. Preliminary investigation conducted by

    the Ohio Department of Health on May 12, 1970, showed that the water in the Willis School was free of coliform contamination, and 18 throat-

    wash specimens processed virologically and bac-

    teriologically yielded no isolates.. Further epide- miologic investigation was then carried out.


    Questionnaire Data. A questionnaire was designed to obtain specific information regarding the nature and duration of the clinical illness, secondary spread and possible modes of spread. It was administered to all full-time and part-time students and faculty of the Wil- lis School, and to several other groups having varying degrees of contact with the affected school.*

    From the questionnaire data an attempt was made to divide the school population into those who were clinically ill and those who were well. Anyone who had any two of the three symptoms of fever, headache and chest pain was considered to be clinically ill. Absentee Data. Absenteeism by date was examined for each city school during the epidemic period; stu- dent visits to the student health service at Ohio Wes- leyan University were similarly analyzed. Serologic Data. Serum samples were obtained from 200 students selected at random at the Willis School and were screened by standard complement fixation technics [3] for antibodies to a battery of respiratory agents, including influenza, para influenza, adenovi- rus, Mycoplasma, selected Coxsackievirus and echo- virus strains, Cl fever, psittacosis and histoplasmosis. Serum was also tested by agar gel immunodiffusion

    *Specific groups questioned: (1) High school students who took shop and cosmetology at the Willis School half a day each day. The shop is located along the corridor be- tween the old and new buildings, and the cosmetology room is on the ground floor of the old building. Both groups ate lunch in the cafeteria. (2) Tutors from the college and high school who helped slow learners one afternoon a week. (3) Substitute teachers during the period between April 20 and May 8. (4) Person? living on the same block as the Willis school (the neighborhood category) who were available for questioning. (5) Faculty and staff from the high school.


    technics for the presence of histoplasmosis M and H precipitin bands [5]. Serum samples were also ob- tained from persons in groups 1,2,3 and 5 (as pre- viously described under questionnaire data) as well as from 50 ninth grade (high school) controls selected at random.

    For the purpose of this study a positive test for histoplasmosis was defined as complement fixation titer of 1:32 or greater for the yeast form and the my- celial (histoplasmin) antigens, and/or the presence in serum of M or H bands by immunodiffusion technics. Skin Test Data. A histoplasmosis skin test survey was conducted four and a half months after the epi- demic peak for all students in the school system to compare rates for the affected and nonaffected schools. In addition, an estimate of the degree of sus- ceptibility of the intermediate school students was de- duced by this method. A permission slip was sent home with each student in the school system; all stu- dents whose parents signed the slips were tested. Environmental Studies. Airflow studies were per- formed by smoke bomb technics to investigate possi- ble spread of contaminated air via the schools forced- air ventilation system as well as other modes of flow.

    A search for possible sources of fungal contamina- tion included collection of samples of soil and bird









    29 30 / 2.3 456 7 89 10,,l2l3141516


    Figure 3. Histoplasmosis cases, by date of onset, Willis students, April 29-May 16, 1970.

    March 1973 The American Journal of Medicine Volume 54 335











    Figure 4. Absenteeism by date, Willis School, April l-May 22, 1970.

    droppings from 73 sites around the Willis school build- ings, including each area of bushes and trees, the parking lots, the center courtyard and the air ducts.


    The Epidemic. The epidemic was explosive in

    nature as can be seen from the epidemic curve

    by date of onset (Figure 3). Most cases occurred on May 6, 7 and 8, with the shape of the curve strongly suggesting a common source outbreak. Although fewer cases had their onset on May 9 and 10, this is probably an artifact due to the fact that these were weekend days and also that the questionnaire was filled out three weeks after the

    peak of the epidemic. The epidemic curve taken from the question-

    naire data is well corroborated by the absentee data (Figure 4) for the Willis School. The usual base line level of absenteeism appeared to be in the range of 45 to 85 students per day. However, on May 7, 144 students were absent, approxi- mately double the base line, and on May 8, 249 were absent, approximately four times the base line. Absenteeism remained elevated during the following week but declined to near base.line lev- els thereafter. These data underestimate absen-

    teeism, since they include only persons absent at the beginning of the day but not those who left during the day. It was estimated that more than 100 persons went home from school during the morning of May 8 causing school officials to ad- journ classes at 1:00 PM.

    Absentee data obtained from each of the other schools in the city for a comparable period of time indicated no increase in absenteeism at any of the elementary schools (which primarily serve

    local neighborhoods), and no increase at the high school (which serves all areas). In addition, the number of students visiting the student health ser- vice at Ohio Wesleyan University, examined by date, showed no peak during the comparable pe- riod. Furthermore, each of the 17 local physicians was questioned, and none could recall treating a case of similar illness (the Willis flu, as it was called) in a person who was not affiliated with the Willis School. Clinical Picture. From personal interviews and the questionnaires, a typical clinical picture emerged. Illness was characterized by fever, headache and chest pain; coryza, sore throat and gastrointestinal symptoms were usually absent. Fever and headache affected 92 and 95 per cent

    336 March 1973 The American Journal of Medicine Volume 54


    of ill persons, respectively, and chest pain af- fected 63 per cent (Table I). Only 56 per cent of the patients had all three symptoms, i.e., fever, headache and chest pain. Anorexia, nausea and cough were also present in more than half of the patients. Seventy-seven per cent were sick enough to stay home from school.

    The chest pain was rather peculiar in nature, characterized as a discomfort in the anterior por- tion of the chest on deep inspiration; it was defi- nitely not pleuritic. The cough, when present, ap- peared later in the course of the illness, usually after two or three days. It was hacking, dry and nonproductive, and was seldom associated with significant disability.

    Figure 5 shows the duration of illness in the students at the Willis School. More than three fourths of the persons affected were ill a week or less. A few persons noted prolonged (more than one month) asthenia, with intermittent low grade fever and easy fatigability. All recovered com- pletely within two months. Five persons were hos- pitalized but only one for longer than a week. Risk of Illness by Association with Willis School. Once it had been established that the illness was associated only with the Willis School, illness rates were analyzed tor each of the various groups associated with the school (Table II) to assess the relative risk conferred by this associa- tion. Rates of illness were high in the first four of these categories (Willis students) being generally higher in girls than in boys. In addition, rates were lower over-all in successive grades being highest in the sixth grade (55 per cent) and lower in the seventh (35 per cent) and eighth (34 per cent) grades. A total of 353 Willis students were clini- cally affected by the epidemic illness. The Willis

    TABLE I Symptoms of 353 Patients with Histoplasmosis

    (Willis Intermediate School Students), April-May 1970

    Symptom Present Absent

    Per cent Unknown Present

    Fever 324 19 10 92 Chills 224 104 25 63 Malaise 226 115 12 64

    Headache 335 16 2 95 Myalgia 132 185 36 37 Chest pain 221 120 12 63

    Cough 186 149 18 53

    Sore throat 148 195 10 42

    Coryza 123 207 23 35 Nausea 208 132 13 59 Vomiting 81 260 12 23

    Anorexia 251 a4 ia 71 Stiff neck 103 229 21 29

    faculty also had a high rate of illness (39 per cent), similar to that in the seventh and eighth grade students.

    Rates of illness for other groups varied (Table II) according to the degree and type of associa- tion. In the cosmetologists and shop students rates were comparable to those in Willis students (52 and 44 per cent, respectively). Generally low rates of illness were found in all other groups in- terviewed.

    Illness rates analyzed by classroom disclosed that no localized area of the school conferred any special risk. Analysis of questionnaires indicated two additional facts: illness rates were similar among those who bought their lunch at school and those who brought it from home; and also there was minimal, if any, secondary spread to family members.


    From the questionnaire and absentee data it was apparent that the epidemic of respiratory illness characterized by headache, fever and chest pain had a common source. It was not related to food, and on culture water from the Willis School water fountains was free of coliform contamination. These factors suggested that the mode of spread was airborne and perhaps related to some com- mon event still to be uncovered.

    Events were sought during the three weeks prior to the epidemic at which large numbers of students might have shared exposure. This time period was selected to include the incubation peri- od for most common infectious agents. There were no assemblies and no unusual large group gatherings, such as picnics, dances or the like.

    DLJAnTlON fDlYS2

    Figure 5. Histoplasmosis cases, by duration of illness, Willis students.

    March 1973 The American Journal of Medicine Volume 54 337


    TABLE II Risk of Illness by Association with the Willis TABLE Ill Serologic Results of Groups Surveyed, Bela- School, April-May 1970 ware, Ohio, April-May 1970

    6th grade M

    F T

    7th grade M F

    T 8th grade

    M F

    T All Willis

    students M

    F T

    Willis faculty and staff


    F T



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