Difference between болезнь and заболевание, ОРВИ and ОРЗ?
Болезнь has a general meaning, заболевание is a term, used by doctors. They both mean the same thing.
ОРЗ (острое респираторное заболевание) is pronounced as о-эр-зэ and it is a more general term than ОРВИ (острое инфекционное вирусное заболевание), pronounced as орви with the last и stressed. In the second case, it is clear that the illness was caused by a virus.
Sorry, ОРВИ - острое респираторное вирусное заболевание.