I've been seeing plays where a player will knowingly send an infected to the survivor block only to terminate them after receiving the $350 survivor reward. This takes the standard $900 for terminating an infected and increasing it to $1,250. There is couple of ideas that might address it. Each time an infected is terminated after admission to the block increases the likelihood of the player being fined and/or terminated by the guards. Survivors in the block may seek to escape or attack the player if they witness what they assumed to be a survivor being terminated in front of them unprovoked.
Additional ideas would be unrest among the survivors if they suspect someone is infected and pressure the player to deal with the individual. Mandatory quarantine of survivors until the player is cleared of oversight. If dogs are added this can increase the risk of being caught as they could alert that infected are present and terminating the dog could also affect the morale of the survivors and result in an additional fine. Achievements can absolutely be themed after these scenarios.