Figure 2

Emergence of ribavirin-resistant PRRSV mutants during sequential passages with ribavirin in MARC-145 cells. Ribavirin-resistant mutants emerged during serial passages of the PRRSV isolate VR2332 in MARC-145 cells in the presence of different concentrations of ribavirin, based on the presence or absence of detectable infectious progeny virus at the end of a 24-hour incubation.