When pathogens enter the body of a host, they do not produce the signs and symptoms of disease immediately. they have to fight the hosts defence mechanism and establish themselves in the host body first. there is an incubation period when the pathogens grow and multiply. Then the signs and symptoms of diseases appear. This is the disease period. The host is infectious during this stage. Finally, , the host may overcome the diseases. This sis the recovery period.
Some disease like influenza and mumps have short incubation periods, while others like syphilis have long incubation periods.
