Transmission of Multidrug-Resistant and Drug-Susceptible Tuberculosis within Households: A Prospective Cohort Study.

BACKGROUND: The "fitness" of an infectious pathogen is defined as the ability of the pathogen to survive, reproduce, be transmitted, and cause disease. The fitness of multidrug-resistant tuberculosis (MDRTB) relative to drug-susceptible tuberculosis is cited as one of the most important determinants of MDRTB spread and epidemic size. To estimate the relative fitness of drug-resistant tuberculosis cases, we compared the incidence of tuberculosis disease among the household contacts of MDRTB index patients to that among the contacts of drug-susceptible index patients. METHODS AND FINDINGS: This 3-y (2010-2013) prospective cohort household follow-up study in South Lima and Callao, Peru, measured the incidence of tuberculosis disease among 1,055 household contacts of 213 MDRTB index cases and 2,362 household contacts of 487 drug-susceptible index cases. A total of 35/1,055 (3.3%) household contacts of 213 MDRTB index cases developed tuberculosis disease, while 114/2,362 (4.8%) household contacts of 487 drug-susceptible index patients developed tuberculosis disease. The total follow-up time for drug-susceptible tuberculosis contacts was 2,620 person-years, while the total follow-up time for MDRTB contacts was 1,425 person-years. Using multivariate Cox regression to adjust for confounding variables including contact HIV status, contact age, socio-economic status, and index case sputum smear grade, the hazard ratio for tuberculosis disease among MDRTB household contacts was found to be half that for drug-susceptible contacts (hazard ratio 0.56, 95% CI 0.34-0.90, p = 0.017). The inference of transmission in this study was limited by the lack of genotyping data for household contacts. Capturing incident disease only among household contacts may also limit the extrapolation of these findings to the community setting. CONCLUSIONS: The low relative fitness of MDRTB estimated by this study improves the chances of controlling drug-resistant tuberculosis. However, fitter multidrug-resistant strains that emerge over time may make this increasingly difficult.

Malaria en una población urbano marginal de Iquitos / Malaria in an urban marginal population of Iquitos

Objetivos: Identificar y describir factores asociados a la presentación de malaria en la población atendida por el Centro de salud de Cardozo. Material y Métodos: Realizamos un estudio epidemiológico transversal con enfoque analítico basado en los resultados de un tamizaje masivo de gota gruesa para el diagnóstico de malaria realizado en la jurisdicción del Centro de Salud de Cardozo en Iquitos, en junio de 1996. Una muestra de 72 personas contestó un cuestionario acerca de factores de riesgo reconocidos en la transmisión de malaria. El grupo casos estuvo constituido por 36 personas quienes tuvieron un resultado de examen gota gruesa positivo a cualquier tipo de malaria; y el grupo control por 36 personas seleccionadas al azar entre los participantes del tamizaje con un resultado negativo. Se realizó un análisis bivariado. La asociación se midió a través de la prueba de Chi2 y la fuerza de asociación se midió por OR. Resultados: La prevalencia de malaria fue de 2.3%. El 72.5% correspondieron a P. vivax y el 27.5% a P. falciparum. Los principales factores asociados a la presentación de malaria fueron los viajes a zona rural (OR=12.14 p<0.001), los viajes a poblados del río Nanay (OR=11.67 p=0.02) y el antecedente de haber presentado antes la enfermedad (OR=12.40 p<0.001). Otros factores asociados fueron la residencia en el AA.HH. Jessica Inchaustegui (OR=6.22 p<0.001) y la residencia cercana a zonas inundables (p=0.040). Por otra parte, se identificó como protector el baño en una habitación cerrada (OR=0.09; p=0.02). Las características personales (edad, sexo, escolaridad y ocupación), de la vivienda (tipo de material), así como la utilización de mosquiteros y de mallas no se asociaron a la presentación de malaria. Conclusiones: El desplazamiento frecuente de la población hacia el río Nanay y las condiciones geográficas de Cardozo, explicarían la prevalencia de malaria en esta área.

Objectives: To identify and to describe the association between malaria and risk factors in the attended population in the Health's Center of Cardozo. Methods: We made a cross-sectional study based on the results of thick drop's screening test for the diagnosis of malaria completed in the jurisdiction of the Center of Health of Cardozo in Iquitos in June of 1996. A sample of 72 people answered a questionnaire about recognized factors of risk in the malaria transmission. The caseswent 36 people who had a positive result of thick drop test to any type of malaria; the control group was formed by 36 people selected at random between all the participants of the thick drop's screening who had a negative result. A bivaried analysis was made. The association was measured through the test of Chi2 and the association force was measured by OR. Results: the prevalence of malaria was of 2.3%; 72.5% corresponded to P. vivax and the 27.5% to P. falciparum. The mainfactors malaria associate went the trips to rural zones (OR=12.14 p<0.001), the trips to towns of the Nanay river (OR=11.67 p=0.02) and the antecedent of malaria (OR=12.40 p<0.001). Other factors associate were the residence in the A.H. "Jessica Inchaustegui" (OR=6.22 p = 0.001) and the residence near inundable zones (p=0.04). On the other hand, it was identified as protection factor the bath in a closed room (OR=0.09 p=0.02). The characteristics of the houses (type of material), personal (age, sex, schooling and occupation) as well as the use of mosquito nettings and meshes; they were not associated upon presentment of malaria. Conclutions: The frequent displacement of the population studied towards the Nanay river and the geographic conditions of Cardozo, would explain the prevalence of malaria in this area.