Certain types of pathogenic micro-organisms may have a widespread distribution in a community without giving evidence of their presence by any characteristic disease. Persons who have recovered from diphtheria, for example, may continue to carry the infectious agent of the disease even though they have acquired immunity. But there are also indications that persons may act as carriers for bacteria to which they have never been specially immunized, and which may, consequently, be a continual menace. Evidently there are times and conditions in which host and parasitic invader become adjusted to each other, so that there is neither an outbreak of disease nor a destruction of the parasite. Presently a change ensues whereby the infectious agent may die out or evidence of active infection may arise.
It is conceivable that an outbreak of harm under these circumstances may be due not only to a decreased resistance of the host but
PARASITISM OF THE HEMOLYTIC STREPTOCOCCUS IN THE UPPER AIR PASSAGES. JAMA. 1923;81(18):1525. doi:10.1001/jama.1923.02650180043018
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