The proposed study aims to understand the dynamics of hepatitis B virus (HBV) infection and factors that influence functional cure among men who have sex with men (MSM). The study will be conducted as a longitudinal cohort study in select cities worldwide, where participants will be enrolled based on their HBV status and undergo regular monitoring for serological and virologic markers. The study endpoints will include HBV DNA, HBsAg, anti-HBc, HBeAg, and occult HBV burden, as well as functional cure (defined as the absence of HBV DNA and serological markers of infection). Sample collection and analysis will involve molecular diagnostic techniques, and statistical analysis will be conducted to account for variables such as age, sex, and baseline HBV load. The expected outcomes of the study include a better understanding of HBV dynamics and factors that influence functional cure among MSM, which can inform the development of new treatment strategies and contribute to the global effort to eliminate HBV infection among high-risk populations worldwide.