when to bring in new rat

Question
Hi Sandra, I have a situation.
An aquaintance of mine had two rats. One of the rats was very sick and they waited to long to get it treated, and the poor rat wouldn't eat or move and was breathing very poorly. So they got it euthanised today.
They are moving and can't take the other rat with them, so i am taking him. I have rats of my own and am aware of the importance of quarantine. But the only place i have is a seperate room in my house, where i intend to keep him for a while first.  
But what i was wondering was, i've read that humans can carry rat respiratory diseases in their lungs for up to 8 hours after coming in contact with an infected rat. So i usually make sure never to see other people's rats unless it will be at least 8 hours till i see mine. But is there an hour requirement like this for rats too.
This rat i'm taking in shows no sign of disease even though he was with the sick rat for quite a while. I will still keep him in a seperate room, but is there a specific amount of hours the disease will be more actively carried in his lungs after being with the sick rat. Like if it were 8 hours like as with humans, i would make sure i don't even bring him in the house until this time is up. The people are moving tomorrow, and a relative of their's has offered to keep the rat for a couple days if absolutely necessary, but they can't keep him for the whole duration of a proper quarantine. So i was hoping for a number of hours that might make the rat less contagious, before they bring him over, example: 8 hours.
I hope that makes sence. I know it sounds very confusing.
So if humans are carriers for 8 hours after, how long are rats carriers.
Thanks!

Answer
Hi Joleen

Just to clear up a misconception and a little quick course on  Bacteriology concerning rats :)

Humans cannot carry any respiratory disease to rats.  The pathogens that cause disease in rats are non pathogenic to humans and vice versa. The ONLY thing that may be transmitted from humans to rats is
Streptococcus pneumoniae bacteria. Sadly, many rat care websites that are written by well intended but very misinformed rat keepers have done well in keeping a huge misconception alive for years, and that is the fact that we can get our rats sick, especially if we have strep throat. These sites claim that the strep that causes strep throat in humans can be passed onto rats and it turns into a deadly pneumonia, which can be fatal in less than 24 hrs of onset.  This is just UNTRUE and basically impossible, since the strep bacteria that causes strep is NON pathogenic to rats, for starters, but is also NOT the same species of strep that causes the deadly and dreaded pneumonia. The bacteria is called Streptococcus pneumoniae also known as pneumococcal pneumonia. Note the difference in spelling above, as this is important since it is totally misunderstood by many rat owners due to mispronunciation of the word entirely.  Rats CAN get pneumococcal pneumonia from humans, but the irony is that a human with this form of pneumonia is usually in the hospital very very sick, not worrying about pet rats etc....
Therefore I cannot give you a solid answer about the incubation time you are looking for since the chance of you harboring any respiratory infection in your lungs and passing it to your rats is very low.

However, if you read over my page on proper quarantine found on my site, sandyscrittercity.com you will find instructions how to "decontaminate" yourself after being in petstores that sell rodents or after being around strange rats that you know nothing about as far as health goes etc....  We CAN carry a virus called SDA, which is a virus that attacks the harderian gland of rodents. This can be carried into our house right on our shoes should we step in infected urine outside our home in the grass after a rodent that carries the virus has urinated there.   Yes it can be that simple to carry in this type of virus.  SDA also adheres to the mucus membranes, which is why I suggest to blow your nose before going around your pet rats as well.  A complete change of clothes, hand washing, removing shoes and blowing your nose is best, but you can just avoid your rats after a hand washing for about 3 hours in case you are carrying SDA virus from whatever source.

If you keep your rats in separate rooms and are sure to take the precautions I wrote above above (and also on my website) go ahead and bring the ratties home to be safe and sound so they can start getting settled in.

Hope this wasnt confusing.....