Detection of EBV-encoded RNA (EBER) via in situ hybridization is the gold standard to determine whether cells contain EBV. I was wondering however whether in EBER-negative cells EBV episomes can still be present.
In replicative cell types latently expressed proteins such as EBNA1 are required to segregate the episome into daughter cells upon replication. Unless the turnover of those proteins is exceptionally low, they would need to be actively expressed to maintain the episome (and latent infection). There are a handful of other latently expressed genes not directly related to episome maintenance that I would expect to see as well, assuming the detection method was sufficiently sensitive.