To develop standard models of HTNV and PUUV infection for future evaluation of vaccines and medical countermeasures, groups of between 10 and 20 hamsters were exposed to serial ten-fold dilutions of either HTNV or PUUV by either the i.m. or i.n. route (from 2-20,000 PFU HTNV or 0.2-20,000 PFU PUUV).