Mosquitoes and Yellow Fever 
209 
this connection various writers have called attention to the menace 
from the Panama Canal. When it is completed, it will allow of 
direct passage from regions where yellow fever is endemic and this 
will greatly increase the possibility of its introduction into these places 
where it is now unknown. The result, with a wholly non-immune 
population, would be appalling. 
On the other hand, there are places wholly outside of the normal 
range of Aedes calopus where the disease has raged. Such are New 
York, Boston, and even Philadelphia, which have suffered notable 
epidemics. These outbreaks have been due to the introduction of 
infected mosquitoes during the heat of summer, when they have not 
only conveyed the disease but have found conditions favorable 
for their multiplication. Or, uninfected mosquitoes have been thus 
accidentally brought in and developed in large numbers, needing 
then only the accidental introduction of cases of the disease to start 
an epidemic. 
Methods of control of various diseases have been revolutionized 
by the discovery that they were insect-borne, but in no other case 
has the change been as radical or the results as spectacular as in the 
case of yellow fever. The “shot-gun quarantine,” the sufferings and 
horrors, the hopelessness of fighting absolutely blindly have given 
way to an efficient, clear-cut method of control, based upon the knowl¬ 
edge that the disease is carried from man to man solely by the mosqui¬ 
to, Aedes calopus. The lines of defense and offense are essentially 
as follows: 
In the first place, when a case of yellow fever occurs, stringent 
precautions must be adopted to prevent the infection of mosquitoes 
and the escape of any already infected. This means that the patient 
must be removed to a mosquito-proof room, or ward beyond reach of 
the insects, and that the infected room must be thoroughly fumi¬ 
gated at once, to kill the mosquitoes hiding within it. All cracks 
and openings should be closed with strips of paper and fumigation 
with burning sulphur or pyrethrum carefully carried out. 
It should be remembered that if the first case noted is that of a 
resident rather than imported, it means that the mosquito carriers 
became infected more than two weeks before the case was diagnosed, 
for as we have seen, the germ must undergo a twelve-day period of 
development within its insect host. Therefore a careful search must 
be made for mild cases which, though unrecognized, may serve as 
foci for the spread of the disease. 
