No don't kill them. People over emphasize this. It's just like people, you don't kill the lady at the grocery store for giving you the flu. Or your child's playmate because they have chicken pox and you are worried your child will get it. Chickens pass on sickness to each other and other birds. Other birds pass on sickness to chickens as well. You shouldn't eat a sick animal. But just like us they generally get over it and become healthy again. Many, many people keep quail and chickens together with no issues. Quail are just more susceptible to getting sick since they haven't been reared in captivity as long. They wouldn't normally be near other birds so their immune system doesn't have to deal with as much in the wild. Just keep them fed well, provide adequate shelter, clean water, security and sanitize their living area from time to time and you should have no troubles of sickness. If so no big deal most things will just work themselves out just as with people. Like people the young and old may have a tougher go at it but that's the nature of things.