There are lots of viruses that persist forever. You can get chickenpox as a kid then die of shingles as a retiree. Measles might give you only mild symptoms the

There are lots of viruses that persist forever. You can get chickenpox as a kid then die of shingles as a retiree. Measles might give you only mild symptoms then 6-15 years after reactivate and cause Subacute sclerosing panencephalitis (SSPE), a fatal brain inflammation with all the interesting symptoms that implies (starting out with mood swings progressing into dementia, muscle spasms and blindness). Think of this the next time some brain dead person starts talking about the "unknown long term effects of the vaccine" - we know what has long term effects, and it's freaking live viruses!