Such scenarios take place in boarding facilities, shows, feedlots and shipping. Concerned about her health I took her to the vet. Many dollars and tests later no diagnosis was given, but the possibility that it could be an allergic reaction was raised. Nothing has helped and she has remained on Cefa tabs since. Also foreign bodies need to be ruled out.
Cancer is a possible cause.
The two most common viruses of dogs which cause respiratory disease are parainfluenza and adenovirus-2. These dog viruses do not have the same reputation for latency and chronicity of shedding that feline respiratory viruses have. And even in the cats, it is a small percentage of cases that are latent or chronic. I wouldn't put odds on both dogs having the same problem, or there being a mold in your house which only bothered dogs, but anything is possible. Because of this, you might do well to have your Yorkshire checked over by your vet.