AMERICAN JOURNAL OF EPIDEMIOLOGY

Copyright © 1976 by The Johns Hopkins University School of Hygiene and Public Health

Vol. 104, No. 5 Printed in U.S.A.

THE RISK OF MENINGITIS AMONG CLASSROOM CONTACTS DURING AN EPIDEMIC OF MENINGOCOCCAL DISEASE JAY A. JACOBSON,1 PAULO AUGUSTO MOREIRA CAMARGOS,2 JOSE TEUBNER FERREIRA2 AND JOSEPH B. McCORMICK '

Jacobson, J. A. (CDC. Atlanta, GA 30333), P. A. M. Camargos, J. T. Ferreira, and J. B. McCormick. The risk of meningitis among classroom contacts during an epidemic of meningococcal disease. AmJ Epidemiol 104:552-555,1976. During an epidemic of meningococcal disease in Belo Horizonte, Brazil, a retrospective survey was carried out to assess the risk of meningitis associated with exposure in a schoolroom. Forty-seven of 17,012 students reportedly had meningitis in August-November 1974, an incidence of 276 per 100,000. Four of 1356 students with classroom exposure to a case contracted meningitis (secondary attack rate, 295 per 100,000). The results indicate that in the population surveyed, 95% of whom were from 7 to 14 years of age, there is no significantly increased risk associated with classroom exposure to a student with meningitis. Antibiotic prophylaxis of classroom contacts is therefore not indicated and should be reserved for contacts known to be at increased risk, such as members of the patient's household or those having direct contact with the patient's oral secretions. disease outbreaks; meningitis, meningococcic; meningococcal infections.

cases in contacts outside the family is not Meningococcal disease, endemic in all well known. More specifically, the risk to parts of the world, has periodically and classroom contacts of patients is unknown, unpredictably produced serious urban epi- even though this group may frequently be demics (1-4). The appearance of even a the object of concern following a case of single fulminant case of meningococcal meningococcal disease in a school. During the meningococcal disease epidisease in a community frequently generdemic in Brazil in 1974 (8), we surveyed a ates considerable anxiety about the risk of large group of classrooms in the city of Belo exposure. Although the risk of secondary Horizonte (state of Minas Gerais) to assess cases in household contacts in epidemic the incidence of meningococcal meningitis and endemic circumstances has been inin schoolchildren and to determine the vestigated (2, 3, 5-7) and found to be secondary attack rate associated with significantly greater than the risk in the general population, the risk of secondary classroom exposure. This is a report of that survey. An outbreak of meningococcal disease Accepted for publication January 19, 1976 and in due to sulfa-resistant serogroup C Neisfinal form April 28, 1976. 1 seria meningitidis began in Sao Paulo, Bacterial Diseases Division, Bureau of Epidemiology, Center for Disease Control, Atlanta, Ga 30333. Brazil, in June 1971 (4). The epidemic (Reprint requests to Dr. Jacobson at this address.) increased step-wise thereafter with peaks 2 State Department of Health, Minas Gerais, Brain each successive winter season. In April zil. The authors gratefully acknowledge the support of 1974 cases due to sulfa-resistant serogroup the Pan American Health Organization, the cooperaA organisms were recognized in Sao Paulo tion of school health supervisors and the assistance of and soon represented approximately 80 per Ms. Margarida Constanca Peixoto Sofal. INTRODUCTION

552

553

MENINGITIS AMONG CLASSROOM CONTACTS

cent of all cases of meningococcal disease. that in August through November there The epidemic increased dramatically soon were 615 reported cases of meningococcal after and spread to involve other Brazilian disease in greater Belo Horizonte for an cities (8). In June 1974, an epidemic of incidence of 50 per 100,000 population both serogroup A and C meningococcal during this 4-month period. Cases in perdisease began in Belo Horizonte. sons age 7 to 14 comprised 31 per cent of 253 laboratory-confirmed cases. Based on METHODS the age distribution of persons with laboraThe epidemiologic characteristics of the tory-confirmed cases, the estimated attack outbreak were determined from data sup- rate for all reported cases in persons age 7 plied by the Health Department of Minas to 14 was 70 per 100,000 persons. Teachers reported on a classroom popuGerais, by the State Health Laboratory, and from records of the two principal Belo lation of 17,012. The mean age of students Horizonte hospitals admitting meningitis in the surveyed classrooms was 10.3 years. Ninety-five per cent of the pupils were 7 to patients. In December 1974, a questionnaire was 14 years of age. The mean classroom size administered to teachers in 569 classrooms was 30.0 students per classroom (standard in 26 schools from high incidence areas that deviation (SD) = 6.50). Of 569 classrooms surveyed, 527 reported enrolled 17,012 pupils aged 7 to 25 years. Information requested included the aver- no cases. Cases were reported from 42 age age of students in a given classroom classrooms. The distribution of cases and their neighborhoods of residence. among the classrooms is shown in table 1. Teachers^ were asked to indicate whether Forty-six of the 47 reported cases were in during the period August through Novem- children 7-14. The observed and expected ber 1974 any of their students had report- frequency of multiple cases in classrooms is edly had meningitis or an unexplained shown in table 2. The occurrence of 47 absence of more than one week, and, if so, cases among 17,012 students covered by to submit the name and address of the the survey represents an incidence of 276 pupil, the date of his illness, and the name per 100,000; for the age group 7-14 it was 286 per 100,000. of the hospital where he was treated. Health department records contained A case was defined as illness in a pupil reported by a teacher to be meningitis. A reports on 32 (68 per cent) of the 47 secondary case was defined in the same teacher-reported cases. The distribution of manner but with the onset of illness more these cases by diagnosis is shown in table 3. than 24 hours and less than 31 days after Of the 15 cases which could not be docuonset of another case in the same class- mented at the health department, three room. If a case meeting this definition was were admitted to hospitals which did not in a sibling of a student with the preceding TABLE 1 case, it was not regarded as a classroomDistribution of cases among classrooms associated secondary case. For the purpose of this study all cases of meningitis reCases in No. children No. classrooms classroom exposed ported by teachers were considered to be of meningococcal etiology. RESULTS

All of the questionnaires were completed and returned. Health Department records indicated

0 1 2 5

527 40 1 1

15,656

Total

569

17,012

1,356

554

JAY A. JACOBSON ET AL. TABLE 2

Observed and expected frequency of cases of meningitis in school classrooms, Belo Horizonte, Brazil, August-November, 1974* Frequency of Cases

No. Classrooms No . reporting No . expectedf

0

1

>2

Total

527 523.9

40 43.3

2 1.8

569 569

* Chi-square test for goodness of fit equals .29, p > .80. t By Poisson Distribution. TABLE 3

Distribution of cases reported to health department by diagnosis Diagnosis

No.

Meningitis Purulent meningitis Meningococcal meningitis Viral meningitis Total

19 7 5 1 32

0.54. This probability is compatible with the hypothesis that classroom-associated secondary cases occur with a frequency not exceeding that predicted by random distribution. The mean number of students in classrooms with secondary cases, 36 (SD 4.24) was not significantly different from that in classrooms with a single case, 32 (SD 6.00) or that of classrooms without a case, 30 (SD 6.50). In the classroom with five cases, three occurred in September and two in October. The two students who became ill in October were siblings. There were 33 pupils in the class with an age range of 11 to 14 years. DISCUSSION

Several points should be emphasized about the limitations of the study. Our case definition focused on meningitis alone rather than on other forms of meningococcal infection such as menincustomarily report cases. Insufficient or gococcemia, pneumonia, arthritis or illegible data on teacher report forms pre- asymptomatic pharyngeal carriage. Howcluded the confirmation of an additional ever, because lay persons and many physisix cases. No cases of meningitis were cians used the term meningitis to include disclosed by searching health department meningococcemia, we do not believe that records for the names of the 243 students cases of meningococcemia were selectively who had unexplained absences. eliminated from our data. Teachers were Five pupils had onset of meningitis 1 to not asked to report students with upper 30 days after classroom exposure to a case. respiratory infections, arthritis or pneuOne of these was a sibling of the student monia because in the absence of confirmawith the preceding case in her classroom. tory laboratory information these illnesses Therefore, four students in two classes were would more likely be due to pathogens regarded as having classroom-associated other than meningococci. secondary cases. There were no coprimary The recorded health department diagnocases. One teacher reportedly had meningi- sis of patients identified as having menintis and died; there were no other cases in gitis was not very helpful in ascertaining the class she taught. For the 1356 students etiology. Thus, our premise that all of the exposed to cases in their classroom, the reported cases were meningococcal rests attack rate for reported meningitis was 295 primarily on the concurrent presence of a per 100,000. All secondary cases were in community-wide meningococcal epidemic classrooms where the average age of stu- and the age distribution of the students we dents was 7-14 years. With use of the surveyed which would make other etiolobinomial distribution P = .00286 cases per gies such as Hemophilus influenza much person, the probability of encountering at less likely. least four cases among 1356 students is Although a study such as this can only

MENINGITIS AMONG CLASSROOM CONTACTS

be accomplished in an epidemic situation, several features of the epidemic complicate the analysis and interpretation of data. During the epidemic, monthly incidence varied, making the chance occurrence of multiple cases in classrooms more likely in some months than in others. Because of the high degree of public awareness and anxiety, many cases in the surveyed population that were reported by teachers as meningitis and considered by us to be meningococcal disease may, in fact, have been other illnesses; thus, cases may have been overreported. The finding of a higher attack rate for the school population surveyed than for the same age group in greater Belo Horizonte is explainable by deliberate selection of schools in neighborhoods where incidence was known to be high. Epidemiologic markers such as serogroups were not available to definitely relate secondary cases to primary ones. The retrospective nature of the survey may have allowed cases to be missed because of faulty absentee records or faulty memories. However, it seems that the net effect of these considerations would be an overestimation of primary and especially secondary attack rates in this analysis. Multiple cases in classrooms did not occur significantly more often than would have been predicted by random distribution. The attack rate for classroom contacts was not significantly higher than the overall attack rate in the school population surveyed. The relative risk for students exposed in a classroom to an individual who developed meningitis was 1.03 with an insignificant attributable risk of 9 per 100,000. When only cases reported to the

555

state health department were analyzed there were no secondary cases in classrooms. The true risk of meningococcal meningitis associated with classroom exposure may be even less than our estimate and almost certainly is not significantly increased compared with the risk to students who are not exposed in classrooms. These findings suggest that antibiotic chemoprophylaxis of school age classroom contacts of persons with meningococcal disease is probably not indicated. The use of such agents is warranted only for persons known to be at increased risk, including household contacts and others having intimate contact with the patient, such as those having direct contact with the patient's oral secretions. REFERENCES

1. Gover M, Jackson G: Cerebrospinal meningitis. A chronological record of reported cases and deaths. Public Health Rep 61:433-450, 1946 2. Pizzi M: A severe epidemic of meningococcus meningitis in Chile, 1941-1942. Am J Public Health 34:231-238, 1944 3. Norton JF, Gordon JE: Meningococcus meningitis in Detroit in 1928-1929. J Prev Med 4:207-214, 1930 4. Souza de Morais J, Munford RS, Risi JB, Antezana E, Feldman RA: Epidemic disease due to serogroup C Neisseria meningitidis in Sao Paulo, Brazil. J Infect Dis 129:568-571, 1974 5. Munford RS, et al: Meningococcal disease: Secondary attack rate and chemoprophylaxis in the United States. JAMA 235(3):261-265, 1976 6. Munford RS, Taunay AE, Souza de Morais J, et al: Spread of meningococcal infection within households. Lancet 1:1275-1278, 1974 7. Kaiser AB, Hennekens CH, Saslaw MS, et al: Seroepidemiology and chemoprophylaxis of disease due to sulfonamide-resistant Neisseria meningitidis in a civilian population. J Infect Dis 130:217-224, 1974 8. Center for Disease Control: Morbidity and Mortality Weekly Rep 23(41):349-350, 1974

The risk of meningitis among classroom contacts during an epidemic of meningococcal disease.

AMERICAN JOURNAL OF EPIDEMIOLOGY Copyright © 1976 by The Johns Hopkins University School of Hygiene and Public Health Vol. 104, No. 5 Printed in U.S...
296KB Sizes 0 Downloads 0 Views