Dogs with mild disease never develop any problems and may live a normal lifespan. (www2.vet.cornell.edu)
At time of writing, the virus had not become more severe, causing mild disease in most sufferers but making a small number — probably less than 1 per cent — extremely ill. (newscientist.com)
To some degree, the clinical signs depend on the severity — mild disease doesn't cause obvious problems, but severe disease often does. (vin.com)