Even viruses that establish chronic infection in the tissues release viral RNA into the blood. Hep C for example is diagnosed with blood antibody and RNA tests. Pretty much the only place you could reasonably expect to have active viral replication with little detectable RNA in the blood is if it was in the brain.
What if there is very little - next to none - replication going on? Just bleb aggregates that accrue over time in biofilms in the brain? Viral RNA released into the blood does seem like a compelling rebut, but in the absence of replication?.
I am fascinated by a theory of immune tolerance. Not so much the one that recently won the Nobel Prize; a version that predates that by around three quarters of a century. Basically it suggests that due to properties inherent to the virus/bacteria/parasite, the body's immune reaction to that agent is suppressed.
It proposes that infectious neuro-tropic agent gets into our brain, often without much immunolgical noise. And it stays there; it is not cleared. None of the typical immunological responses occur, there is no abnormal bloodwork, no antibodies, no inflammation. But a slow chronic incapacitation overtakes the infected. Without the benefit of immune fingerprints.
This was talked about back in the 50's, during the height of the Cold War, but it doesn't appear to have gotten much traction in the public, perhaps for good reason. I'm still researching it, but it's a slow go with my brain. I don't know how issues such as the release of viral RNA into blood impact the theory. There is not a lot written on it that I can find.
But, it's fascinating because I can see it potentially fitting - even with the timing of the Royal Hospital outbreak back in the '50's. And it presupposes a persistent infectious agent.
Is it right? Probably not. But it's possible. Ultimately it's merely one more theory in a long string that I've been trying to get my arms around , with an eye to confirming or debunking.