Epidemiology of a Tuberculosis Outbreak in a Rural Missouri High School

Abstract

ABSTRACT. Objectives. 1) Demonstrate the importance of maintaining a tuberculosis (TB) control program even in low-incidence areas by studying a TB-contact investigation of a highly infectious high school student in rural Missouri, and 2) discuss factors that perpetuated or contained this school-based outbreak.Methods. A case review of the index patient, a 15-year-old high school student, established estimates of his level and duration of infectiousness. Contact investigations of his household (n ‫؍‬ 5), high school (n ‫؍‬ 781), and school bus (n ‫؍‬ 67) were administered according to guidelines established by the Centers for Disease Control and Prevention. High school students were stratified further based on classroom exposure, and relative risks were calculated for each risk group.Results. The case review revealed that the index patient had evidence of a pulmonary cavity on chest radiograph 6 months before his TB diagnosis. Of the 5 household contacts, all were infected and 3 (60%) had developed active TB disease. Of the 781 high school students sought for TB screening, 559 (72%) completed testing, and 58 (10%) were PPD-positive. Sixty-seven bus riders were sought for testing and 7 (19%) were purified protein derivative (PPD)-positive, with 1 bus rider subsequently diagnosed with active disease.Risks were calculated based on classroom and bus exposure to the patient. The relative risks for a positive PPD were 3.2 for attending any class with the patient (n ‫؍‬ 25), 4.2 for classes with less ventilation (n ‫؍‬ 21), and 5.7 for >3 classes (n ‫؍‬ 7) with the patient. A total of 62 students started treatment for latent TB infection, and 49 have completed it. Forty-two of these students received directly observed therapy through the local public health agency and the high school.Conclusion. This investigation demonstrated widespread adult-type transmission from a pediatric TB case with a 6-month delay in diagnosis. Several actions contributed to the success of this investigation, including rapidly mobilizing the public health system, centralizing follow-up, and on-site testing and treatment with directly observed therapy. Pediatricians need to maintain awareness of TB and risk factors in children, even in lowincidence areas. Prompt diagnosis would have reduced the severity of illness in the patient and potentially prevented widespread school-based transmission. Public health authorities must maintain an infrastructure to respond to large TB outbreaks. Pediatrics 2004; 113:e514 -e519. URL: http://www.pediatrics.org/cgi/ content/full/113/6/e514; tuberculosis disease, latent tuberculosis infection, directly observed therapy, school-based outbreak, contact investigation.

Tuberculosis outbreak among students in a boarding school

“…Overall, 41.5% of the school students had TST results of o5 mm; this included 49.4% of close and 36.5% of remote contacts. These rates are higher compared with those reported by PHILLIPS et al [14], who investigated a TB outbreak in a USA high school with a 10% TST positivity in the school students and 19% in students sharing a school bus, presumably close contacts. BAILY et al [21] presented a model aimed to improve TB contact investigation by including variables predicting a positive TST among contacts of an active TB case.…”

“…The high proportion of completion of treatment (91.3%) is noteworthy compared with other observations [14]. This high rate was achieved by the local public health and TB clinic teams working inside the school and providing DOT-based preventive therapy in the school with remarkable cooperation of the students, school administration and personnel, and the students' parents.…”

“…The environmental conditions and the level of infectiveness of a case are the primary risk factors for outbreaks. As opposed to young children, who are likely to develop systemic illness and are usually not infective, adolescents tend to develop infective pulmonary disease, similar to the presentation of disease in adults [13,14]. The level of infectiveness of a case affects the probability of further infection, based on degree of pulmonary involvement, presence of cavitations and positive sputum smears [1].…”

Mycobacterium tuberculosisGrowth Control by Lung Macrophages and CD8 Cells from Patient Contacts

“…The proportions of individuals that undergo primary infection with Mtb or reactivation disease after aerogenic Mtb exposure are usually low (3,5,6). Healthy household contacts (HHCs) of patients constitute a protected group, as only 5 to 10% of individuals exposed in households develop reactivation TB during their lifetime (3) and 50 to 75% do not acquire Mtb infection as determined by tuberculin skin testing (TST) (7,8).…”

Contact tracing of a 15-year-old girl with smearnegative pulmonary tuberculosis in Tehran

“…Since children are more asymptomatic or have weaker cough than adults, and usually have a smaller bacterial load, little attention has been paid to the transmission of TB from a child. Several TB outbreaks have been reported in schools but the index case was rarely a child [2,3]; the source of infection was usually adults. Early case detection and diagnosis of TB and supervised treatment are vital for control and reduction of TB and are part of the components of the Stop TB strategy [4]].…”