This brief describes training held in Liberia to prepare research technicians, One Health-Design Research and Mentorship (OH-DReaM) working group members, and STOP Spillover Liberia team members to collect and test samples from rodents for the presence of Lassa virus RNA—an indication of infection. The research was conducted to understand whether the distribution of Lassa fever in Liberia extends beyond the previously identified "Lassa belt.