In recent years persons who are known as disease carriers have been
looked on as important factors in the spread of many contagious
diseases. The part they play in diphtheria has been abundantly
demonstrated and is important. Carriers in this sense are persons who
are well, but who carry about disease germs in their throats or noses.
They may have recently passed through mild attacks of the disease whose
germs remain for a long time after recovery, or they may have received
the germs from sick persons, never having been sick. This condition of
carriage may persist a long time, and carriers are especially dangerous
because not usually suspected.