Glynn Judith R, Guerra-Assunção José Afonso, Houben Rein M G J, Sichali Lifted, Mzembe Themba, Mwaungulu Lorrain K, Mwaungulu J Nimrod, McNerney Ruth, Khan Palwasha, Parkhill Julian, Crampin Amelia C, Clark Taane G
Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, United Kingdom.
Karonga Prevention Study, Chilumba, Malawi.
PLoS One. 2015 Jul 16;10(7):e0132840. doi: 10.1371/journal.pone.0132840. eCollection 2015.
The proportion of tuberculosis attributable to transmission from close contacts is not well known. Comparison of the genome of strains from index patients and prior contacts allows transmission to be confirmed or excluded.
In Karonga District, Malawi, all tuberculosis patients are asked about prior contact with others with tuberculosis. All available strains from culture-positive patients were sequenced. Up to 10 single nucleotide polymorphisms between index patients and their prior contacts were allowed for confirmation, and ≥ 100 for exclusion. The population attributable fraction was estimated from the proportion of confirmed transmissions and the proportion of patients with contacts.
From 1997-2010 there were 1907 new culture-confirmed tuberculosis patients, of whom 32% reported at least one family contact and an additional 11% had at least one other contact; 60% of contacts had smear-positive disease. Among case-contact pairs with sequences available, transmission was confirmed from 38% (62/163) smear-positive prior contacts and 0/17 smear-negative prior contacts. Confirmed transmission was more common in those related to the prior contact (42.4%, 56/132) than in non-relatives (19.4%, 6/31, p = 0.02), and in those with more intense contact, to younger index cases, and in more recent years. The proportion of tuberculosis attributable to known contacts was estimated to be 9.4% overall.
In this population known contacts only explained a small proportion of tuberculosis cases. Even those with a prior family contact with smear positive tuberculosis were more likely to have acquired their infection elsewhere.
由密切接触者传播所致的结核病比例尚不清楚。对索引患者及其既往接触者的菌株基因组进行比较，可确认或排除传播情况。
在马拉维的卡龙加区，询问所有结核病患者之前是否与其他结核病患者有过接触。对所有培养阳性患者的可用菌株进行测序。索引患者与其既往接触者之间允许有多达10个单核苷酸多态性用于确认传播，≥100个则用于排除。根据确认传播的比例和有接触者的患者比例估算人群归因分数。
1997年至2010年期间，有1907例新的培养确诊结核病患者，其中32%报告至少有一名家庭接触者，另有11%至少有一名其他接触者；60%的接触者患有涂片阳性疾病。在有可用序列的病例-接触者对中，38%（62/163）涂片阳性的既往接触者被确认有传播，而17例涂片阴性的既往接触者中无传播被确认。与既往接触者有亲属关系的人群中确认传播更为常见（42.4%，56/132），高于非亲属人群（19.4%，6/31，p = 0.02），在接触更密切、索引病例更年轻以及近年的人群中也是如此。已知接触者所致结核病的总体比例估计为9.4%。
在该人群中，已知接触者仅解释了一小部分结核病病例。即使是那些之前与涂片阳性结核病患者有家庭接触的人，也更有可能是在其他地方感染的。
