HIV prevalence in Indonesia is increasing, and only 64% of infected individuals know their status. In a prospective cohort of 1,453 hospitalized patients with unexplained fever, 46 (3.2%) had HIV, including 15 (1.1%) patients without a prior HIV diagnosis. Among 31 subjects previously known to have HIV, 21 (68%) had been receiving combination antiretroviral therapy (cART) at the time of enrollment. Of 39 HIV cases with HIV RNA levels ≥ 100 copies/mL, sequencing for genotype analysis and resistance testing was successful in 30 (77%) subjects. The most common HIV subtypes were AE (90%) and B (10%). Five (16.7%) subjects had resistance mutations to nucleoside and non-nucleoside reverse transcriptase inhibitors, and all of them were on cART. No evidence of transmitted drug resistance was found in newly diagnosed individuals. Hospital-based screening may be an efficient method to expand HIV testing and identify a significant number of new cases. Access to care, close monitoring, expansion of anti-retroviral options, and ensuring availability of CD4 determinations, viral load testing, and genotyping are crucial to control of the epidemic in Indonesia.