C型肝炎病毒(hepatitis C virus, HCV)與愛滋病毒(human immunodeficiency virus, HIV)皆藉由血體液傳播，除了過去認為靜脈藥癮者(injecting drug user, IDU)藉由污染針具而造成高比例的愛滋病毒感染合併C型肝炎，近年來藉由性行為傳播C型肝炎的發生率也逐漸上升，尤其是男男間性行為者(men who have sex with men, MSM)。感染C型肝炎的相關危險性行為，包含無套肛交、網路交友、以藥助性、群交等。病患能夠藉由自然清除或是藥物治療清除體內C型肝炎病毒，但並無法生成具有保護性的免疫抗體，因此會因為持續進行風險行為而再次感染(reinfection)。根據分子流病(molecular epidemiology)觀察出C型肝炎病毒主要基因型別有地域之間的差異，男男間性行為與靜脈藥癮族群或風險行為有可能交互傳播。目前指引建議所有18歲以上者皆接受一次的常規檢測，對於具有風險者，則需要增加檢測頻率；如愛滋病毒感染具有風險者，需每年檢測。檢測的流程為先檢測C型肝炎抗體(anti-HCV antibody)，若陽性再檢測病毒核酸(HCV RNA)；但對於免疫力低下者、六個月內感染者、再次感染者，則要加上C型肝炎病毒核酸作為輔助診斷。急性C型肝炎的治療與慢性C型肝炎一致，使用直接抗病毒藥物(direct-acting antivirals, DAAs) 8-12週療程。治療上不須等待觀察患者是否能自然清除，診斷即治療(test and treat)的策略不僅符合經濟成本效益(costeffectiveness)，也能達成愛滋病感染族群C型肝炎微消除(micro-elimination)的目標。

Hepatitis C virus (HCV) and human immunodeficiency virus (HIV) share the similar bloodborne transmission route. While the majority of patients coinfected with HIV and HCV are injecting drug users (IDUs), the epidemic of sexually transmitted HCV infection has emerged mainly among men who have sex with men (MSM). Sexually transmitted HCV infection has been linked to high-risk sexual behaviors, such as condomless anal sex, online social networking, chemsex, and group sex. Viral clearance of primary HCV infection may occur spontaneously or after treatment, but it does not confer immunity against subsequent HCV reinfection. Molecular epidemiology has revealed regional differences in major circulating variants, and the complexity of HCV transmission networks between IDU and MSM communities. Current HCV guidelines recommend one-time, routine HCV testing for all individuals aged 18 years and older. Periodic repeat HCV testing should be provided to individuals with at-risk behaviors or exposures. Annual HCV testing is recommended for HIV-positive individuals with ongoing risk. HCV testing should be initiated with anti-HCV antibody, and followed by a confirmatory nucleic acid test for HCV (HCV RNA). For individuals with immunocompromised status, HCV exposure within the past 6 months, and HCV reinfection, testing for HCV RNA should be performed. Patients with acute HCV infection should be treated with the same regimens that are recommended for chronic HCV infection. “Test and treat” strategy, without awaiting spontaneous resolution, has been shown to be cost-effective and lead to micro-elimination.