It is present in most brains.
Congenital transmission is possible.
It is associated with a wide range of diseases. There is possible pathogenic interaction with other viruses. It is frequently misdiagnosed or not diagnosed at all. HHV-6B is more likely than 6A to be detected in blood and saliva. HHV-6B strains there is very little sequence divergence, suggesting that variants 6A and 6B may, in fact, represent two distinct viruses.