Further more, Computer. Should any vessel, regardless of designation, enter our current sector without having made prior contact with us raise shields immediately. Reference Starfleet General Order 12 as basis.
edited to add:
Scan all returning crew members to the ship and compare with most recent biological scan. Should any annomolies be it altered brain waves or unidentified organisms be detected, inform CMO immediately and put a level 1 quarantine field around affected crew member.