Time travel works...just invented, by you. The tests prove it!
After many conversations and significant planning, your epidemiologist significant other has approved your plans for time travel, forward or backwards. You are both satisfied that if you do bring back some dread disease, the only person who will die is you; not everyone else.
However, as a time traveler, you're a strong student of history and are aware that ideas can be just as infectious as biological pathogens. For example, sending fully formed Marxist ideas back to the end of feudalism in the 1500's would have a profound effect on the history of Europe. Likewise, bringing an old but forgotten idea forward can have similarly profound effects.
As much as possible, you'd like to be able to rejoin society after your travels but worry about bringing some contagious idea with you when you come back. How does this time traveler handle the risks of being infected with a contagious idea then spreading it to his fellow humans on return to his own time?
The same disclaimer applies: you don't have to worry about the Grandfather Paradox or causality or any of the other nasty time travel problems. Physical security of the time machine itself is also taken care of, so no worries of theft or breaking & entering. The time machine also includes a 99% accurate universal translator that permits bidirectional communication between you and whoever you're talking to (if you don't have this translator then you don't stand much chance of getting infected, eh?).