Marcos Rodríguez Pedro Jorge, Díaz-Cabanela Daniel, Ursua Díaz María Isabel, Fernández-Albalat Ruiz María, Verea Hernando Héctor
Servicio de Neumología, Complejo Hospitalario Universitario Juan Canalejo, A Coruña, España.
Arch Bronconeumol. 2007 Nov;43(11):611-6. doi: 10.1016/s1579-2129(07)60138-4.
The aim of this study was to describe 5 microepidemics of tuberculosis occurring in schools, establish the risk factors associated with the outbreaks, assess how well a concentric circles strategy for contact tracing predicts infection, and assess the usefulness of genotyping strains in the analysis of the outbreaks.
The study assessed 5 epidemic outbreaks of tuberculosis using a standard contact tracing procedure. The outbreaks occurred in 2 day nurseries and 2 high schools between 1998 and 2005. Contacts were stratified using a concentric circle system based on level of exposure. DNA fingerprints of the available strains were determined based on the restriction fragment length polymorphism (RFLP) IS6110 and compared with the contact study to interpret the transmission of the infection.
We analyzed 5 outbreaks. Eighty-five contacts were analyzed in the first outbreak, 519 in the second, 116 in the third, 655 in the fourth, and 102 in the fifth. The rate of infection was 31%, 29%, 66%, 37.6%, and 32%, respectively. Secondary cases of active disease were detected: 9 in the first outbreak, 16 in the second, 5 in the third, 6 in the fourth, and 13 in the fifth. RFLP analysis revealed that a single strain was involved in 3 of the outbreaks, and in a fourth, at least 2 strains were involved. In outbreaks 2, 3, and 5, there was a significant association between the degree of contact and the probability of infection (P< .05). In all of the outbreaks, the relative risk of developing the disease was associated with the level of exposure.
Analysis of contacts based on concentric circles of risk predicts the likelihood of infection. RFLP facilitates analysis of complex transmission routes that are not detected using traditional methods of contact screening.
本研究旨在描述在学校发生的5起结核病微型流行，确定与疫情暴发相关的危险因素，评估同心圆式接触者追踪策略预测感染情况的效果，以及评估菌株基因分型在疫情分析中的作用。
本研究采用标准的接触者追踪程序评估5起结核病疫情暴发。这些疫情暴发于1998年至2005年期间在2家日托所和2所高中发生。根据接触程度，使用同心圆系统对接触者进行分层。基于限制性片段长度多态性（RFLP）IS6110确定可用菌株的DNA指纹，并与接触者研究结果进行比较，以解释感染的传播情况。
我们分析了5起疫情暴发。在第一起疫情中分析了85名接触者，第二起519名，第三起116名，第四起655名，第五起102名。感染率分别为31%、29%、66%、37.6%和32%。检测到活动性疾病的二代病例：第一起疫情中有9例，第二起16例，第三起5例，第四起6例，第五起13例。RFLP分析显示，3起疫情由单一菌株引起，在第四起疫情中，至少涉及2种菌株。在第二、第三和第五起疫情中，接触程度与感染概率之间存在显著关联（P<0.05）。在所有疫情中，发病的相对风险与接触程度相关。
基于风险同心圆对接触者进行分析可预测感染的可能性。RFLP有助于分析传统接触者筛查方法未检测到的复杂传播途径。
