The Home Medical Library, Volume 1…
“ Whooping cough is usually more or less prevalent in all thickly settled civilized communities, at times is epidemic, and often follows epidemics of measles. It occurs chiefly in children from six months to six years of age. Girls and all weak and delicate subjects are slightly more susceptible to the disease. Some children are naturally immune to whooping cough. One attack usually protects against another.Development.—A variable period elapses between the time of exposure to whooping cough and the appearance of the first symptoms. ”
