[Microepidemics of tuberculosis; apropos of 2 school outbreaks in the area 15 of the Valencia community].

Schools are settings with high concentrations of young people with little exposure to Mycobacterium tuberculosis and greater risk of developing disease when infection occurs as the result of sporadic localized outbreaks. We studied two outbreaks in two elementary schools (A and B) after two cases of bacilliferous pulmonary tuberculosis were detected in teachers in 1990 and 1994. Contacts were trace din school A by the primary care physician and in school B by the pneumologist and public health authorities. Contacts were classified as belonging to the risk group (RG) or the low risk group (LRG). The RG was composed of 187 contacts in school A and 59 in school B. Individuals in the LRG numbered 429 and 116 respectively. Mantoux positives numbered 108 in the RG and 45 in the LRG in school A (p < 0.001). In school B 50 RG individuals and 29 LRG individuals were positive (p < 0.001). The proportion of Mantoux positives was greater in the RG of school B than in the RG of school A (p < 0.01), probably owing to longer time of evolution of disease and possible laryngeal involvement in the index case. Likewise, tuberculin positives were fewer in the LRG of school A than in the LRG of school B (p < 0.001), owing to the small size of the LRG in school A. Thirteen cases of tuberculosis were seen in school A, six of which called for drug prophylaxis after contacts were traced. The nature of the index case and the conditions of exposure are both important in such outbreaks, demonstrating the need to act appropriately to trace contacts, preferably under the supervision of a pneumologists.