Phase I or Fast Track proposals will be accepted. Direct-to-Phase II proposals will not be accepted. Number of anticipated awards: 2-3 Budget (total costs): Phase I: $ 300,000 for up to 1 year Phase II: $ 2 million for up to 3 years Background Viral infections due to hepatitis B virus (HBV) and hepatitis C virus (HCV) are major global public health burdens, and account for more than 3.0 million new cases and over 1.1 million deaths each year (WHO 2020). Despite the existence of a safe and effective vaccine for HBV, and effective antiviral medications for HCV cure, diagnosis and linkage to care are poor in both developing and high-income countries. Consequently, 80-90% of all people living with HBV and HCV remain undiagnosed and untreated each year, leading to increased morbidity and death due to cirrhosis and hepatocellular carcinoma (HCC). In the United States alone, it is estimated that only 15% of all people living with HBV are aware of their status, and of these, only 4.5% are treated. These global gaps highlight the critical need for novel, innovative, and improved strategies to target hard-to-reach populations and facilitate earlier detection, diagnosis, and linkage to care and treatment for people living with HBV and HCV. Experiences and lessons learned from implementation of HIV self-testing strategies, and the COVID-19 pandemic, have demonstrated the importance of self-testing as an approach to increase access to and uptake of testing among key populations, including many first-time testers. HIV and viral hepatitis infections share common modes of transmission and social and structural barriers to accessing care and services among key populations, including men who have sex with men (MSM), injection drug users (IDUs), and commercial sex workers. Of the estimated 38 million people living with HIV (PLWH), 2.7 and 2.3 million people are estimated to be coinfected with HBV and HCV, with a global prevalence of 7.4 and 6.2 percent, respectively (WHO 2020). Coinfection with HIV significantly impacts the pathogenesis of HBV and HCV and is associated with reduced spontaneous clearance of HCV and HBsAg, higher rates of chronicity and occult HBV, higher HCV viral loads, rapid disease Page 108 progression, and increased risk of morbidity and mortality due to cirrhosis and HCC. Integrated strategies for screening and diagnosis of HIV and viral hepatitis infections are therefore critical to an effective global health response. Technological innovations, including the development of multiplexed patient administered (e.g., self-collection, selftesting) tests, have the potential to overcome barriers to healthcare access and stigma, increase access to testing, facilitate early diagnosis and treatment initiation, reduce transmission, and improve linkage to care and health outcomes for currently undiagnosed and hard-to-reach populations who have either never been tested or have limited access to clinical care.