Infection route (bActeria or virus via the pharyngotympanic tube into middle ear is the maximum incidence in childhood (2Infection via the external meatus is liable to occur when a tympanic membrance perforation is present otitis media arising as a blood-borne infection is rareInfection route  ①Bacteria or virus via the pharyngotympanic tube into middle ear is the maximum incidence in childhood.  ②Infection via the external meatus is liable to occur when a tympanic membrance perforation is present.  ③otitis media arising as a blood-borne infection is rare