The Peep Show actor, who plays Greg Preston in the BBC One programme about a handful of survivors struggling to stay alive after a deadly virus wipes out most of the world's population, said: "When we went in for the readthrough, the first thing he (the director) said when I came in through the door was, 'You know you're being shot?', I said, 'That's absolutely fine,' and he said, 'You'll probably be in the next series.'
"And then the producer said the same thing, an executive from the BBC said the same thing... and then I began to get worried."
But Paterson wouldn't confirm how long his character will be seen in the second series, which also stars Julie Graham.
"I'm definitely in the first episode - how long I continue, you'll have to watch and see," he said.
Paterson also said the second series would be "much darker" than the first, adding: "Things that were underlying tensions in the first series will need to be resolved between the characters in this series."
:: Survivors returns to BBC One on Tuesday, January 12.