HIV/AIDS remains social, health, and economic threat for Africa, particularly sub-Saharan Africa countries. Viral replication continued to be a major challenge among patients living with HIV and on antiretroviral treatment. However, information with virological failure was not well investigated. Thus, this study was aimed to assess Incidence of virological failure and associated factor among adult HIV-patients on first line antiretroviral therapy regimen in, Ethiopia. A retrospective cohort study design, 5 years of follow up, was conducted through reviewed and analyzed data of 445 adult patients who had started ART between January 01, 2013 and April 30, 2018. The Kaplan–Meier method was used to estimate the probability of virological failure at different time points. Incidence of virological failure was calculated per 100 Person-years. The Cox proportional hazards model was used to identify factors associated with virological failure. The study results showed that out of the total 445 cohort patients who were assessed for viral load, there were 40 (9.0%) virological failures in 1,594 person years of retrospective follow-up. This makes the incidence rate of virological failure 2.5 per 100 person-years of follow-up. The cumulative hazard of virological failure at 1 year, 2 years, 3 years, 4 years and 5 years after starting ART amongst those tested was 1.1%, 4.3%, 6.6%, 9.9% and 12.3% respectively. Young ages (15-24 years), poor adherence, having short duration on ART taking and changing ART regimen were risk factors significantly associated with virological failure. In conclusion, considerable incidence of virological failure among HIV positive individuals on treatment was observed. Therefore, develop the strategies and targeted interventions to the above factors by stakeholders can minimize virological failure. 

Keywords: Incidence, Virological Failure, Factors, Ethiopia