The herpes virus attaches itself to the nerves, including nerves in the central nervous system. 

Neal Stephenson speculates in his novel Snow Crash (1993) that these viruses could be used by clever programmers working in the shuttle zone between computer code and genetic code as little messengers of DNA that could send information, coded missives, directly into the brain by splicing the message onto the nervous system itself.

Like a very suggestive successful novel, that.