Corynebacterium diphtheriae enters the body, infecting the tissues of the throat and tonsils. The organism spreads from
healthy carriers or infected individuals to susceptible individuals by airborne droplets. Previous infection or immunization provides resistance to the effects of the potent diphtheria exotoxin. Death from diphtheria is usually due to a combination of the effects of partial suffocation and tissue destruction by exotoxin. In untreated infections, the toxin can cause systemic damage to the heart (about 25% of diphtheria patients develop
myocarditis), kidneys, liver, and adrenal glands.