First- and second-line treatments have been freely provided to eligible patients since 2007, and treatment initiation and monitoring has been guided by clinical and/or immunological data. In this study, we evaluated the long-term virological outcome and implications for second-line regimens after 36 months ART in patients treated according to the WHO public health approach in Cameroon. Methods Study site and patients From September 2008 to September 2009, we conducted a cross-sectional study among ARV-treated patients attending a reference treatment unit, the H?pital de Jour of the Yaound Central Hospital. (98.7%) started on a first-line regimen that included 3TC +d4T/AZT+NVP/EFV. Sixty-six (17.6%) patients experienced virological failure (VL1000 copies/ml) and 53 carried a resistant virus, thus representing 81.5% (53/65) of the patients who failed. Forty-two out of 53 were resistant to nucleoside and non-nucleoside reverse-transcriptase inhibitors (NRTIs+NNRTIs), one to protease inhibitors (PI) and NNRTIs, two to NRTIs only and eight to NNRTIs only. Among patients with NRTI resistance, 18/44 (40.9%) carried Thymidine Analog Mutations (TAMs), and 13/44 (29.5%) accumulated at least three NRTI resistance mutations. Observed NNRTI resistance mutations affected drugs of the regimen, essentially nevirapine and efavirenz, but several patients (10/51, 19.6%) accumulated mutations that may have compromised etravirine use. Conclusions We observed a moderate level of virological failure after 36 months of treatment, but a high proportion of patients who failed developed drug resistance. Although we found that for the majority of patients, second-line regimens recommended in Cameroon would be still effective, accumulated resistance mutations are of concern and may compromise future treatment strategies, stressing the need for virological monitoring in resource-limited settings. strong class=”kwd-title” Keywords: HIV-1, treatment outcome, virological monitoring, drug resistance, resource-limited country, Cameroon Introduction Antiretroviral therapy (ART) has significantly reduced morbidity and mortality in human immunodeficiency virus type 1 (HIV-1)-positive patients in both industrialized and resource-poor countries. Because ART can fail as a result of toxicity, pretreatment HIV-1 drug resistance, insufficient patient adherence or incomplete suppression of viral replication leading to the emergence of drug-resistant viruses, adequate clinical and biological management can significantly improve treatment outcome and can prevent rapid failure [1,2]. Current World Health Organisation (WHO) recommendations favour the use of viral load monitoring [3], but its practical feasibility is still challenging in the context of resource-poor countries, essentially because of the high cost. Drug resistance evaluation can provide helpful information for treatment switch by guiding the selection of appropriate ARV regimens when a treatment failure is diagnosed, but the technology and assays are still very expensive and hard to implement locally due to inadequate infrastructures and lack of specialized personnel. Despite these limitations in ART access and monitoring, recent studies assessing the outcome of ART in the developing world have shown significantly good results, with good virological success achieved after 12 and/or 24 months of ART, and even limited effects of observed drug resistance mutations for second-line options [4,5]. In addition, few clinical tests, comparing both the medical plus laboratory-based approach versus the public health monitoring approach only, have not clearly identified significant variations in terms of viral suppression and the emergence of drug resistant strains, as well as deaths [6,7]. The main limitation of Angelicin some of these studies is the short period of evaluation, and, consequently, little is known about the long-term effects of this strategy in terms of the build up of drug resistance mutations and possible effects for second- and/or third-line treatments. Since the 2000s, ART access in Cameroon has been significantly improved through the implementation of the WHO simplify approach and the decentralization of ART services. The standard first-line therapy consists of two nucleoside reverse transcriptase inhibitors (NRTIs) and one non-NRTI (NNRTI), and until 2010 when WHO recommended the alternative of stavudine with tenofovir, research first-line antiretrovirals (ARVs) in Cameroon included zidovudine or stavudine plus lamivudine as NRTIs and nevirapine or efavirenz as NNRTIs. First- and second-line treatments have been freely provided to qualified individuals since 2007, and treatment initiation and monitoring has been guided by medical and/or immunological data. In this study, we evaluated the long-term virological end result and implications for second-line regimens after 36 months ART in individuals treated according to the WHO general public health approach in Cameroon. Methods Study site.We thank all contributors who directly or indirectly participated in the successful completion of this study: the Ministry of General public Health of Cameroon, individuals and all health-care staff and laboratory staffs. Competing interests The authors have no competing interests to declare. Authors’ contributions AFA, CK, ED and MP contributed to the study concept and design. who received PMTCT, were ART-na?ve at treatment initiation, and 371/376 (98.7%) started on a first-line routine that included 3TC +d4T/AZT+NVP/EFV. Sixty-six (17.6%) individuals experienced virological failure (VL1000 copies/ml) and 53 carried a resistant disease, RAB25 as a result representing 81.5% (53/65) of the individuals who failed. Forty-two out of 53 were resistant to nucleoside and non-nucleoside reverse-transcriptase inhibitors (NRTIs+NNRTIs), one to protease inhibitors (PI) and NNRTIs, two to NRTIs only and eight to NNRTIs only. Among individuals with NRTI resistance, 18/44 (40.9%) carried Thymidine Analog Mutations (TAMs), and 13/44 (29.5%) accumulated at least three NRTI resistance mutations. Observed NNRTI resistance mutations affected medicines of the regimen, essentially nevirapine and efavirenz, but several individuals (10/51, 19.6%) accumulated mutations that may possess compromised etravirine use. Conclusions We observed a moderate level of virological failure after 36 months of treatment, but a high proportion of individuals who failed developed drug resistance. Although we found that for the majority of individuals, second-line regimens recommended in Cameroon would be still effective, accumulated resistance mutations are of concern and may compromise future treatment strategies, Angelicin stressing the need for virological monitoring in resource-limited settings. strong class=”kwd-title” Keywords: HIV-1, treatment end result, virological monitoring, drug resistance, resource-limited country, Cameroon Intro Antiretroviral therapy (ART) has significantly reduced morbidity and mortality in human being immunodeficiency disease type 1 (HIV-1)-positive individuals in both industrialized and resource-poor countries. Because ART can fail as a result of toxicity, pretreatment HIV-1 drug resistance, insufficient individual adherence or incomplete suppression of viral replication leading to the emergence of drug-resistant viruses, adequate medical and biological management can significantly improve treatment end result and may prevent rapid failure [1,2]. Current World Health Organisation (WHO) recommendations favour the use of viral weight monitoring [3], but its practical feasibility is still demanding in the context of resource-poor countries, essentially because of the high cost. Drug resistance evaluation can provide helpful info for treatment switch by guiding the selection of appropriate ARV regimens when a treatment failure is diagnosed, but the technology and assays are still very expensive and very difficult to implement locally due to inadequate infrastructures and lack of specialized staff. Despite these limitations in ART access and monitoring, recent studies assessing the outcome of ART in the developing world have shown significantly good results, with good virological success accomplished after 12 and/or 24 months of ART, and even limited effects of observed drug resistance mutations for second-line options [4,5]. In addition, few clinical tests, comparing both the medical plus laboratory-based approach versus the public health monitoring approach alone, have not clearly recognized significant differences in terms of viral suppression and the emergence of drug resistant strains, as well as Angelicin deaths [6,7]. The main limitation of some of these studies is the short period of evaluation, and, consequently, little is known about the long-term effects of this strategy in terms of the build up of drug resistance mutations and possible effects for second- and/or third-line treatments. Since the 2000s, ART access in Cameroon has been significantly improved through the implementation of the WHO simplify approach and the decentralization of ART services. The standard first-line therapy consists of two nucleoside reverse transcriptase inhibitors (NRTIs) and one non-NRTI (NNRTI), and until 2010 when WHO recommended the alternative of stavudine with tenofovir, research first-line antiretrovirals (ARVs) in Cameroon included zidovudine or stavudine plus lamivudine as NRTIs and nevirapine or efavirenz as NNRTIs. First- and second-line treatments have been freely provided to qualified individuals since 2007, and treatment initiation and monitoring has been guided by medical and/or immunological data. With this study, we evaluated the long-term virological end result and implications for second-line regimens after 36 months ART in individuals treated according to the WHO general public health approach in Cameroon. Methods Study site and individuals From September 2008 to September 2009, we carried out a Angelicin cross-sectional study among ARV-treated individuals attending a research treatment unit, the H?pital de Jour of the Yaound Central Hospital. In this unit, individuals received ART as per national recommendations, and.