Abstract
Simian betaretroviruses include the well-known exogenous simian retroviruses (SRV-1 through SRV-8), and some closely related simian endogenous retroviruses (SERV). Here, we characterized two new viral genomes, which appear to represent novel SERVs but have characteristics of both SRV and SERV highlighting the need to develop new assays providing molecular and serologic differentiation of SERV and SRV to avoid false positives.