Whooping cough is a very contagious disease which is contracted by
most children during early years. Occasional persons who have escaped
it in childhood are affected in adult life. Second attacks are rare.
Sometimes a mother or nurse, who has had whooping cough in childhood,
will again contract the disease when caring for children who are
suffering from it. In distinction to most of the contagious diseases,
whooping cough frequently occurs in infants less than a year of age,
and the mortality associated with it is due largely to this fact. In
Chicago from 1911 to 1922, out of 39,233 cases of whooping cough 1,630
were fatal. This represents one death out of every 24 patients, and
corresponds very closely to the death rate in scarlet fever during the
same period and is about three times as high as that in measles. Of 97
deaths from whooping cough in Chicago during 1922, 58 were in children
under 1 year of age, and all but one were in children under 5 years.
This serves to emphasize the importance of protecting young children
from the disease as long as possible.
The cause of whooping cough appears to be a very minute bacillus which
is found in the secretions from the upper respiratory tract. The action
of this germ seems to be through poisons which it produces. The disease
is transferred from one person to others through small particles of
the secretions which are thrown out into the air during coughing. These
moist particles being inhaled, gain a lodgement in the throat and thus
cause another case. The time after exposure before symptoms appear is
indefinite. Exact dates are hard to fix, but the incubation period is
often very short. It may vary from five to fifteen days.