Further update...

[x-cyclops.livejournal.com]

The virus that infected Betsy was apparently bioengineered - I suppose that's obvious, given that it only affects psis. (By the way, the rest of the psis in the house have been tested, right down to Rachel, and they're all clean, so however this thing gets transmitted, it's clearly not airborne.) We don't know for sure where she was infected, but if you account for a reasonable incubation period, the possibility that she picked it up in Peru, where we were after all in a bioweapons lab seems fairly plausible. She did have close physical and telepathic contact with the guards we turned over to the Peruvian government.

But Betsy should be just fine, and the bug is quite comprehensively dead, so I think we've dodged yet another medical catastrophe quite neatly.