ICSE Class 9 Answered

(a) Classification of diseases on the basis of extent of occurrence:
(1) Endemic diseases
(2) Epidemic diseases
(3) Pandemic diseases
(4) Sporadic diseases

(b)

Pandemic disease: When the occurrence of the disease is worldwide, it is known as a pandemic disease. E.g. AIDS.
Sporadic disease: The disease occurring in single, scattered cases is known as a sporadic disease. E.g. Malaria, Cholera.