YOUNG BIRD SICKNESS/DISEASE ~ has over recent years become, by fanciers, a collective term. It is actually a combination of a few different viruses with Circovirus often the initial cause. Whilst some diseases have similar symptoms none are as virulent.
Provided well established and sound methods of disease prevention or damage limitation are applied correctly with effective, proven medication then your birds can survive this dreadful condition.
TREATMENT: Wonder Pigeon