Background: Prevalence of immunological failure has been shown to be high in some African countries. Few studies however have assessed the magnitude of virological failure in Tanzania. This study aimed at determining virological failure and its associated factors in north western Tanzania.

Methods: A cross sectional study was conducted among HIV-infected patients who were receiving first line ART at Bugando medical centre. Virological loads were measured and socio-demographic and clinical information were collected for analysis. Patients with a single viral load of> 10,000 copies/ml were coded as having virological failure as per WHO definition and poor adherence level was defined as any adherence level of< 95%. Data analysis was done using STATA 11 to determine the proportion of patients with virological failure and its associated factors.

Results: In total 274 patients were enrolled and, 43 (15.7%) met the criteria of virological failure. The odds of having virological failure were independently associated with baseline CD4 counts of< 200 cells/µl (AOR= 8.6 (1.7-42.1), p= 0.008), poor adherence (AOR= 15.4 (6.6-36.1), p< 0.0001) and Nevirapine based regimen (AOR= 4.1 (1.6-10.4), p= 0.003).

Conclusion: Virological failure is prevalent among HIV patients on first line ART. Test and treat, adherence counseling and regular virological monitoring could optimize the virological outcome of HIV patients receiving first line ART in Tanzania and similar setting.