Virus filtration is a robust mechanism to ensure virus safety of biotherapeutic manufacturing processes and must be validated under simulated worst case processing conditions to meet regulatory expectations. This presents several risks including: virus breakthrough resulting from low pressure/depressurization (stop/start), implementation of prefilters, complexities of intensified or fully continuous processes, and therapeutic products from new manufacturing modalities like advanced therapy medicinal products (ATMPs). The recent update to PDA Technical Report No. 41 and the pending update to ICH Q5A is evidence of these new challenges and reflects our increased knowledge regarding worst case parameters for virus filtration. This video covers a summary of the regulatory changes and outlines the detailed mechanisms governing effective virus filtration, demonstrating how both specific methods and advanced filter design can overcome these challenges.