system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Where do viruses go when there's not an outbreak?

Common example --- every year there's flu season. Where is the flu when it's not flu season? 

Topical example --- they've apparently identified patient zero of the current ebola outbreak as a child who died in December 2013. Ebola obviously has had outbreaks in the past. Where did ebola go in between outbreaks? Is it just hiding somewhere in the jungle? If so, now that ebola has escaped Africa, does this mean it could be lurking somewhere in Europe or the United States and, years from now, there could be an outbreak that starts outside of Africa?

Does this mean something that was once widespread in the US that we're now all vaccinated against --- say, smallpox --- could be lurking in my backyard and is just waiting for some anti-vaccination fool to stumble upon it?
gpt
Virologist here! Think of a virus like a grizzly bear. When winter comes, the bear knows it needs to go in to hibernation to reserve its strength, rest through harsh times, and re-emerge in better conditions. Viruses do the exact same thing.