The phrase
"outside germs" refers to the bacteria, viruses, or other harmful microorganisms that can enter our bodies from the environment around us. These germs can make us sick if we don't take precautions to keep them away.
Full definition
All people entering the room must wear a cap and surgical mask to prevent spreading
outside germs into the room.
Tracking
less outside germs from your shoes into your home can also help keep pets and children with a tendency to spend time on the floor healthier all year round.