[Izzy]

Also, the big one to be worried about as far a zoonotic diseases (spreadable to humans) is chlamidia or psittacosis. Birds can carry it without signs of illness, and it is especially dangerous for people if untreated - similar to a cold as far as symptoms.

The best way to guage your birds health is to have them checked out by an avian vet and have blood work done to see their white blood cell count - which can indicate any disease/illness. There are specific tests for many diseases as well which can be recommended based upon the bird's history/appearance.