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An outbreak of tuberculosis in an Oxfordshire School
Br. J. Dis. Chest (1987) 81, 293
AN OUTBREAK OF TUBERCULOSIS OXFORDSHIRE SCHOOL A. J. FREW*, R. T. MAYON-WHITE?
IN AN
AND M. K. BENSON*
* Osler Chest Unit, Churchill Hospital, Oxford OX3 7W; ? Department of Community Medicine, Manor House, Headington, Oxford OX3 9DZ
Summary
A primary schoolteacher was found to have pulmonary tuberculosis. Subsequent investigations showed that nine of her 32 pupils had been infected. The problem is discussed in the light of current recommendations designed to protect schoolchildren. Case Report A 36-year-old female schoolteacher developed a productive cough during August 1984. She became non-specifically unwell in September but did not seek medical attention until she developed haemoptysis and night sweats at the end of October. A chest radiograph showed cavitation in the right upper lobe and her sputum contained acid-fast bacilli which proved to be Mycobacterium tuberculosis on culture. Her father had contracted pulmonary tuberculosis 31 years before, but she was not thought to have been infected at that time. At the age of 13 she had a negative Heaf reaction and subsequently received BCG vaccination. A chest radiograph when she started teaching at the age of 22 was reported to have been normal. This woman worked almost exclusively with a classof 32 children aged 7 years but her duties also included supervision of other children during meals and running the school library. It was apparent that although children in her classwere at greatest risk, most of the 314 children attending the school had been exposed to possible infection and the contact programme was set up accordingly. After discussion with the schoolteacher and the headmistress, the parents of all children at the school were contacted and informed of the possibility of infection. Heaf tests were performed a week later on all the children and 37 adult staff members. Six children had grade 2 or 3 Heaf reactions and three of these had radiographic evidence of primary pulmonary tuberculosis. Three other children with equivocal reactions (grade l-2) had negative Mantoux tests at 1 in 1000. Six weeks later their skin reactions had not increased and they were therefore considered to have had previous infection with atypical mycobacteria. Ten members of staff had negative Heaf tests. The 27 staff members with positive reactions had normal chest radiographs. Heaf tests were repeated after 6 weeks on all contacts whose initial reaction was negative or grade 1. Three children were identified whose reactions had become positive (grade 2 or 3). All nine children with evidence of infection were members of the classtaught by the infected teacher. None of the negative staff members converted. Correspondence to: Dr A. J. Frew, Department of Allergy and Clinical Immunology, Cardiothoracic Institute, Brompton Hospital, London SW3 6HP.
294
BR.
J. DIS.
CHEST:
VOL.
81 NO.
3
Single agent chemotherapy (isoniazid 6 mg/kg daily) was given to the six children with skin test evidence of infection, and dual therapy (rifampicin 10 mg/kg and isoniazid 6 mg/kg daily) was given
to the three with radiographic changes. DISCUSSION This outbreak, though small, caused considerable local concern and we have reviewed our actions in the light of recommendations issued 4 years ago by the Joint Tuberculosis Committee of the British Thoracic Society (1). Our patient had cavitating disease with large numbers of acid-fast bacilli in the sputum and therefore there was a high risk of infection especially to the children in her class with whom she had prolonged close contact. The other children attending the school were exposed to a much lower degree but in view of the high level of parental concern, all children attending the school were screened. It is noteworthy that despite the high infection rate in our patient’s class (nine out of 30) none of the other children or staff showed evidence of infection. The schools’ BCG programme was abandoned in Oxfordshire 5 years ago, amid some local and national criticism (2). This present outbreak cannot be attributed to the change in vaccination policy, since the teacher had received BCG and the children were below the age at which they would previously have received BCG. The fact that the children had not received BCG means that the tuberculin skin test is a reliable indicator of infection. Although conversion may take 6 weeks following exposure, there is general agreement upon the practice of screening immediately and again at 6 weeks after the final exposure. It remains policy to offer BCG to school staff on entry to the profession if they have negative tuberculin tests and no evidence of previous BCG vaccination. The rationale for this practice is that although they do not have an increased risk of contracting tuberculosis, the potential consequences of infection to schoolchildren are unacceptable. We were therefore disquieted to find that 10 out of 37 of this school’s staff had negative skin tests. Since 1982, schoolteachers in England and Wales have not been required to have chest radiographs before entry to the profession (3). We would agree with this policy except for those with a history of previous exposure to tuberculosis and those resident in areas with a high local incidence of tuberculosis. The previous policy did not in fact prevent the present outbreak and raises the question of whether annual screening might have picked up disease at an early stage. The incidence of new cases in the population is so low at present that this is not a cost effective measure. The most important advice to teachers is that they should seek early medical advice if they develop respiratory illnesses. Prophylactic antituberculous chemotherapy remains a controversial topic. There is no doubt that the three children with radiographic evidence of infection needed combination chemotherapy. The rationale of prophylactic antituberculous chemotherapy in the other children is to prevent progression of the primary infection and to reduce the likelihood of reactivation in later life. The action taken depends primarily on the risk of developing active disease. It is difficult to obtain an accurate estimate of risk but recent figures from Edinburgh suggest that these children have a 5-year risk of developing active disease of between 0.02 and 0.4% (N. Horne, personal communication). The United States Public Health Service in Alaska showed that isoniazid used as a single agent was well tolerated and gave effective prophylaxis if it was taken for at least 10
FREW.
MAYON-WHITE,
BENSON:
TB IN AN OXFORDSHIRE
SCHOOL
295
months (4). Combination chemotherapy may allow the duration of treatment to be reduced but causes an increased incidence of adverse reactions. At present prophylactic antituberculous chemotherapy is recommended for individuals with evidence of recent infection. If the risk of developing progressive infection continues to decline, it may become preferable to observe infected individuals and only treat those in whom the disease progresses. In these days of financial stringency, the specialized tuberculosis contact tracing service is under attack. This outbreak reminds us that despite the best precautions, outbreaks will continue to occur and demonstrates the importance of careful contact tracing. REFERENCES 1. Joint Tuberculosis Committee of the British Thoracic Society. Control and prevention of tuberculosis: a code of practice. Br Med J 1983;287: 1118-21. 2. Miller CL, Morris J, Pollock TM. PHLS inquiry into current BCG vaccination policy. Br Med J 1984;288:564. 3. Chief Medical Officer. Education Act 1980; Education (teachers) regulations 1982. London: Dept of Education and Science, 1982. 4. Comstock GW, Ferabee SH, Hammes LM. A controlled trial of community-wide isoniazid prophylaxis in Alaska. Am Rev Resp Dis 1967;95:935-43.
Date accepted 28 August
1986
AN OUTBREAK OF TUBERCULOSIS OXFORDSHIRE SCHOOL A. J. FREW*, R. T. MAYON-WHITE?
IN AN
AND M. K. BENSON*
* Osler Chest Unit, Churchill Hospital, Oxford OX3 7W; ? Department of Community Medicine, Manor House, Headington, Oxford OX3 9DZ
Summary
A primary schoolteacher was found to have pulmonary tuberculosis. Subsequent investigations showed that nine of her 32 pupils had been infected. The problem is discussed in the light of current recommendations designed to protect schoolchildren. Case Report A 36-year-old female schoolteacher developed a productive cough during August 1984. She became non-specifically unwell in September but did not seek medical attention until she developed haemoptysis and night sweats at the end of October. A chest radiograph showed cavitation in the right upper lobe and her sputum contained acid-fast bacilli which proved to be Mycobacterium tuberculosis on culture. Her father had contracted pulmonary tuberculosis 31 years before, but she was not thought to have been infected at that time. At the age of 13 she had a negative Heaf reaction and subsequently received BCG vaccination. A chest radiograph when she started teaching at the age of 22 was reported to have been normal. This woman worked almost exclusively with a classof 32 children aged 7 years but her duties also included supervision of other children during meals and running the school library. It was apparent that although children in her classwere at greatest risk, most of the 314 children attending the school had been exposed to possible infection and the contact programme was set up accordingly. After discussion with the schoolteacher and the headmistress, the parents of all children at the school were contacted and informed of the possibility of infection. Heaf tests were performed a week later on all the children and 37 adult staff members. Six children had grade 2 or 3 Heaf reactions and three of these had radiographic evidence of primary pulmonary tuberculosis. Three other children with equivocal reactions (grade l-2) had negative Mantoux tests at 1 in 1000. Six weeks later their skin reactions had not increased and they were therefore considered to have had previous infection with atypical mycobacteria. Ten members of staff had negative Heaf tests. The 27 staff members with positive reactions had normal chest radiographs. Heaf tests were repeated after 6 weeks on all contacts whose initial reaction was negative or grade 1. Three children were identified whose reactions had become positive (grade 2 or 3). All nine children with evidence of infection were members of the classtaught by the infected teacher. None of the negative staff members converted. Correspondence to: Dr A. J. Frew, Department of Allergy and Clinical Immunology, Cardiothoracic Institute, Brompton Hospital, London SW3 6HP.
294
BR.
J. DIS.
CHEST:
VOL.
81 NO.
3
Single agent chemotherapy (isoniazid 6 mg/kg daily) was given to the six children with skin test evidence of infection, and dual therapy (rifampicin 10 mg/kg and isoniazid 6 mg/kg daily) was given
to the three with radiographic changes. DISCUSSION This outbreak, though small, caused considerable local concern and we have reviewed our actions in the light of recommendations issued 4 years ago by the Joint Tuberculosis Committee of the British Thoracic Society (1). Our patient had cavitating disease with large numbers of acid-fast bacilli in the sputum and therefore there was a high risk of infection especially to the children in her class with whom she had prolonged close contact. The other children attending the school were exposed to a much lower degree but in view of the high level of parental concern, all children attending the school were screened. It is noteworthy that despite the high infection rate in our patient’s class (nine out of 30) none of the other children or staff showed evidence of infection. The schools’ BCG programme was abandoned in Oxfordshire 5 years ago, amid some local and national criticism (2). This present outbreak cannot be attributed to the change in vaccination policy, since the teacher had received BCG and the children were below the age at which they would previously have received BCG. The fact that the children had not received BCG means that the tuberculin skin test is a reliable indicator of infection. Although conversion may take 6 weeks following exposure, there is general agreement upon the practice of screening immediately and again at 6 weeks after the final exposure. It remains policy to offer BCG to school staff on entry to the profession if they have negative tuberculin tests and no evidence of previous BCG vaccination. The rationale for this practice is that although they do not have an increased risk of contracting tuberculosis, the potential consequences of infection to schoolchildren are unacceptable. We were therefore disquieted to find that 10 out of 37 of this school’s staff had negative skin tests. Since 1982, schoolteachers in England and Wales have not been required to have chest radiographs before entry to the profession (3). We would agree with this policy except for those with a history of previous exposure to tuberculosis and those resident in areas with a high local incidence of tuberculosis. The previous policy did not in fact prevent the present outbreak and raises the question of whether annual screening might have picked up disease at an early stage. The incidence of new cases in the population is so low at present that this is not a cost effective measure. The most important advice to teachers is that they should seek early medical advice if they develop respiratory illnesses. Prophylactic antituberculous chemotherapy remains a controversial topic. There is no doubt that the three children with radiographic evidence of infection needed combination chemotherapy. The rationale of prophylactic antituberculous chemotherapy in the other children is to prevent progression of the primary infection and to reduce the likelihood of reactivation in later life. The action taken depends primarily on the risk of developing active disease. It is difficult to obtain an accurate estimate of risk but recent figures from Edinburgh suggest that these children have a 5-year risk of developing active disease of between 0.02 and 0.4% (N. Horne, personal communication). The United States Public Health Service in Alaska showed that isoniazid used as a single agent was well tolerated and gave effective prophylaxis if it was taken for at least 10
FREW.
MAYON-WHITE,
BENSON:
TB IN AN OXFORDSHIRE
SCHOOL
295
months (4). Combination chemotherapy may allow the duration of treatment to be reduced but causes an increased incidence of adverse reactions. At present prophylactic antituberculous chemotherapy is recommended for individuals with evidence of recent infection. If the risk of developing progressive infection continues to decline, it may become preferable to observe infected individuals and only treat those in whom the disease progresses. In these days of financial stringency, the specialized tuberculosis contact tracing service is under attack. This outbreak reminds us that despite the best precautions, outbreaks will continue to occur and demonstrates the importance of careful contact tracing. REFERENCES 1. Joint Tuberculosis Committee of the British Thoracic Society. Control and prevention of tuberculosis: a code of practice. Br Med J 1983;287: 1118-21. 2. Miller CL, Morris J, Pollock TM. PHLS inquiry into current BCG vaccination policy. Br Med J 1984;288:564. 3. Chief Medical Officer. Education Act 1980; Education (teachers) regulations 1982. London: Dept of Education and Science, 1982. 4. Comstock GW, Ferabee SH, Hammes LM. A controlled trial of community-wide isoniazid prophylaxis in Alaska. Am Rev Resp Dis 1967;95:935-43.
Date accepted 28 August
1986