Age
In India, polio is essentially a disease of infancy and childhood. About 50 per cent of cases are reported in infancy. The most vulnerable age is between 6 months and 3 years.

Sex
Sex differences have been noted in the ratio of 3 males to one female.

Risk factors of Polio
Several provocative or risk factors have been found to precipitate an attack of paralytic polio in individuals already infected with polio viruses. The include fatigue, trauma, intramuscular injections, operative procedures such as tonsillectomy under taken especially during epidemics of polio and administration of immunizing agents particularly alum containing DPT.

Environmental factors for Polio
Polio is more likely to occur during the rainy season. Approximately 60- per cent of cases recorded in India were during June to September.