Someone noted (vedtopkar) these are "HHV-6 and HHV-7, which cause roseola". Note that it's an incredibly common infection in babies.

There's also another study investigating association between HHV-6 and measles virus serology and brain antibody in autism:

https://www.ncbi.nlm.nih.gov/pubmed/9756729

Reading these studies makes me think an ineffective blood-brain barrier or a brain-specific defence might trigger common viruses to present a wider family of brain-related diseases.

We also know there is literature on encephalitis caused by both HHV-6 and measles. I'm speculating that even in a micro, benign form, this condition is enough the shake brain structure.

We should probably investigate a more complex but more generic model of brain diseases.