In the middle of the night when toileting my pup I saw a stray dog running scared past our house. I got my pup indoors and went to find the stray. He was desperate, obviously lost and needing help so I brought him into the garden (not the house) and phoned around.
No-one could help in the night so I gave the dog water and a snack and some bedding and left him in the garden until the RSPCA emergency number opened at 7am.
Sadly, he has found a way out and gone so I can no longer help him. 
My question is: How long before I can allow my pup into the garden again without risk of exposure to anything infectious? He has had his first jab and will have the second on Monday. We have a back yard which the stray had no access to, so my plan is to restrict the pup to the yard until monday when I can ask my vet's advice.
But if anyone here had any knowledge of the period during which ground touched by a potentially infected dog may be a hazard, I would be very grateful.