A prospective longitudinal study of tuberculosis among household contacts of smear-positive tuberculosis cases in Lima, Peru.
Household contacts (HHCs) of TB cases are at increased risk for TB disease compared to the general population but the risk may be modified by individual or household factors. We conducted a study to determine incident TB among HHCs over two years after exposure and to identify individual and household level risk factors.



Adults newly diagnosed with a first episode of smear-positive pulmonary TB (index cases) between March 2010 and December 2011 in eastern Lima, were interviewed to identify their HHC and household characteristics. TB registers were reviewed for up to two years after the index case diagnosis and house visits were made to ascertain TB cases among HHC. The TB incidence rate ratio among HHCs as a function of risk factors was determined using generalized linear mixed models.



The 1178 index cases reported 5466 HHCs. In 402/1178 (34.1 %) households, at least one HHC had experienced a TB episode ever. The TB incidence among HHCs was 1918 (95%CI 1669-2194) per 100,000 person-years overall, and was 2392 (95%CI 2005-2833) and 1435 (95%CI 1139-1787) per 100,000 person-years in the first and second year, respectively. Incident TB occurred more than six months following the index case's TB diagnosis in 121/205 (59.0 %) HHCs. In HHCs, bacillary load and time between symptoms and treatment initiation in the index case, as well as the relationship to the index case and the sex of the HHC all had a significant association with TB incidence in HHCs.



Incidence of TB among HHCs was more than ten times higher than in the general population. Certain HHC and households were at higher risk of TB, we recommend studies to compare HHC investigation to households at highest risk versus current practice, in terms of efficiency.
Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Av. Honorio Delgado 430, San Martín de Porres, Lima 31, Peru. Larissa.otero@upch.pe.|Department of Public Health, Unit of General Epidemiology and Disease Control, Institute of Tropical Medicine, Antwerp, Belgium. Larissa.otero@upch.pe.
Larissa
L
Otero
Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Canada.
Lena
L
Shah
Department of Public Health, Unit of Epidemiology and Control of Tropical Diseases, Institute of Tropical Medicine, Antwerp, Belgium.
Kristien
K
Verdonck
Department of Public Health, Unit of General Epidemiology and Disease Control, Institute of Tropical Medicine, Antwerp, Belgium.
Tullia
T
Battaglioli
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
Timothy
T
Brewer
Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Av. Honorio Delgado 430, San Martín de Porres, Lima 31, Peru.
Eduardo
E
Gotuzzo
Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Av. Honorio Delgado 430, San Martín de Porres, Lima 31, Peru.
Carlos
C
Seas
Department of Public Health, Unit of General Epidemiology and Disease Control, Institute of Tropical Medicine, Antwerp, Belgium.|Department of Public Health, Ghent University, Ghent, Belgium.
Patrick
P
Van der Stuyft
D000293:Adolescent; D000328:Adult; D002648:Child; D016358:Contact Tracing; D005191:Family Characteristics; D005260:Female; D006801:Humans; D015994:Incidence; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D010568:Peru / Q000453:epidemiology; D011446:Prospective Studies; D012307:Risk Factors; D013183:Sputum / Q000382:microbiology; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000453:epidemiology* / Q000635:transmission; D055815:Young Adult
Household contact investigation; Longitudinal study; Multilevel analysis