After a little searching, it looks like arenavirus does indeed have a segmented genome, if a little slight compared to influenza. It seems to only be able to reassort with closely related viruses, however. Meaning, it seems to have an easy time swapping gene fragments with another arenavirus like Lassa.

Here's an overview of arenavirus variations: www.mdpi.com/1999-4915/5/1/241/pdf-vor
However, the freaky part comes at page 248: "Serial passages of arenaviruses in cell lines or animals could lead to the accumulation of mutations changing the viral phenotype from the natural reservoirs or from clinical samples "

Does this sound familiar to any of you? Remember when the story broke that some scientists were able to create a killer strain of the influenza virus in lab just by creating cell lines? ( [link to www.independent.co.uk]

Yeah, same concept...

I'm officially a tiny bit freaked out.