epiy tl ’ Munson: Cholera Carriers 9 
cholera presenting a high case mortality, the proportion of per- 
sons who are carriers without presenting symptoms of the 
disease will be relatively small. Possibly this may be due to 
the fact that in such an epidemic the strain of germ concerned 
is so virulent that if introduced into the system the average 
power of vital resistance is insufficient to check the invader and 
the host promptly sickens and usually dies. Conversely, where 
the case mortality is light, the lack of virulence in the germ 
will probably permit it to be harbored in many cases without 
the production of symptoms, and a considerable percentage of 
carriers may be expected. 
The recent outbreaks in the provinces and Manila have pre- 
sented most clearly these two distinct types of infection: the 
provincial case mortality has been nearly twice that of Manila 
and relatively very few cholera carriers have been found. 
But we must bear in mind the possibility that an apparently 
mild strain of cholera germ, under conditions of environment 
as yet not fully understood by us, may acquire a high degree 
of virulence and change the type of disease from one of a 
relatively benign character to one of a most fatal type. This 
adds to the necessity of seeking out and removing the concealed 
sources of infection found in cholera carriers. 
One of the most apparent lessons to be learned from these 
recent experiences relates to the possible period of latent in- 
fection in cholera and its bearing on the period of incubation 
and quarantine heretofore accepted for health work. It is un- 
doubtedly true that the five-day period usually accepted for in- 
cubation and quarantine ordinarily will suffice for the control 
of infection in the majority of cases; but it is equally true that 
such a period does not hold good in a very considerable number 
of instances, which sheds much light on cholera situations not 
otherwise readily explainable. For example, convict 30351, who 
died of cholera, might have traveled halfway around the world, 
scattering his infection broadcast during his eighteen-day period 
as a carrier, and died of true cholera in a place many thousands 
of miles from any other source of infection. There is a warn- 
ing in such cases that health officers all over the world would 
do well to heed. 
In conclusion, in such outbreaks as that recently in Manila, 
the carriers would seem to be not only the most numerous but 
the most insidious and dangerous sources of infection. The 
prompt eradication of a general cholera infection, therefore, | 
includes the detection and isolation of carriers as a scientific 
prerequisite. 
