Your carpet already has most of the same bacteria and germs in it as your friends pet soiled carpet because they are brought into your home on your feet every time you go outside. Even if you’re fastidious about removing your shoes at the door, general foot traffic will spread germs throughout your house.
For piece of mind you can clean and sanitize the bottom of your carpet cleaner, as well as its wheels, nozzle, brushes, etc., any parts that come into contact with the floor. You’ll also want to wash out the recovery tank. Wipe the carpet cleaner down with a rag to remove surface grime, then apply any non-bleach sanitizer according to the product label’s instructions. Finish by wiping down the carpet cleaner with a clean rag and you’ll be good to go.