RESEARCH ARTICLE Open Access Tuberculosis infectious pool and associated factors in East Gojjam Zone, Northwest Ethiopia Mulusew Andualem Asemahagn 1* , Getu Degu Alene 1 and Solomon Abebe Yimer 2,3 Abstract Background: Globally, tuberculosis (TB) lasts a major public health concern. Using feasible strategies to estimate TB infectious periods is crucial. The aim of this study was to determine the magnitude of TB infectious period and associated factors in East Gojjam zone. Methods: An institution-based prospective study was conducted among 348 pulmonary TB (PTB) cases between December 2017 and December 2018. TB cases were recruited from all health facilities located in Hulet Eju Enesie, Enebse Sarmider, Debay Tilatgen, Dejen, Debre-Markos town administration, and Machakel districts. Data were collected through an exit interview using a structured questionnaire and analyzed by IBM SPSS version25. The TB infectious period of each patient category was determined using the TB management time and sputum smear conversion time. The sum of the infectious period of each patient category gave the infectious pool of the study area. A multivariable logistic regression analysis was used to identify factors associated with the magnitude of TB infectious period. Results: Of the total participated PTB cases, 209(60%) were male, 226(65%) aged < 30 years, 205(59%) were from the rural settings, and 77 (22%) had comorbidities. The magnitude of the TB infectious pool in the study area was 78,031 infectious person-days. The undiagnosed TB cases (44,895 days), smear-positive (14,625 days) and smear- negative (12,995 days) were major contributors to the infectious pool. The overall average median TB management time was 142.4 days (IQR, 98–238 days). Similarly, the average sputum smear conversion time of PTB cases (new and repeat) was 46 days. Residence, knowledge, form of TB, smoking, alcohol history, distance from the facility, comorbidity history and stigma were statistically significant factors TB infectious period (p-value< 0.05). Conclusions: The magnitude of the TB infectious pool is high even if it is lower than the findings of previous studies. This might be an indicator of poor access to TB services, service delays, low community awareness, impaired facility readiness, and poor transportation. Improving personal awareness and behavior, timely management of commodities, and using the TB management time in TB control are crucial to improving TB control activities. Keywords: TB management time, TB infectious pool, Factors, East Gojjam zone, Ethiopia © The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. * Correspondence: muler.hi@gmail.com 1 School of Public Health, College of Medicine and Health Sciences, Bahir Dar University, Bahir Dar, Ethiopia Full list of author information is available at the end of the article Asemahagn et al. BMC Pulmonary Medicine (2019) 19:229 https://doi.org/10.1186/s12890-019-0995-3