Propagated epidemic is characterized by person to person transmission and also by slow rise of cases followed by a plateau phase and then gradual decline. A point source epidemic is characterized by a sudden rise of cases.
*India is a polio free country so If a new case of polio occurs now in India, through fecooral route there is a possiblity of spread of infection to another individual and give rise to large no of cases but it will be difficult to spread the infection or large no of cases because everyone has taken routine Immunization and pulse polio so immunity is fairly strong.
*If by chance one case comes in contact with a child who has not received complete immunization or his immunity is low then maybe another case might occur and then another however this will be characterized by a SLOW rise of CASES hence this is an example of propagated epidemic.
*Vitamin A bottle once opened can be stored at room temperature up to 60 days.