The continuance of an
epidemic on shipboard, as on the land, must depend upon the presence of
infected mosquitoes and of nonimmune individuals. Under these conditions
we can readily understand why the disease should not be carried from the
West Indies or from South America to the Mediterranean, to the east
coast of Africa, or to Asiatic seaport cities. On the other hand, if the
disease could be transmitted by infected clothing, bedding, etc., there
seems no good reason why it should not have been carried to these
distant localities long ago.
The restriction as regards altitude, however, probably depends upon the
fact that the mosquito which serves as an intermediate host is a coast
species, which does not live in elevated regions. It is a
well-established fact that yellow fever has never prevailed in the City
of Mexico, although the city has constant and unrestricted intercourse
with the infected seaport, Vera Cruz. Persons who have been exposed in
Vera Cruz during the epidemic season frequently fall sick after their
arrival in the City of Mexico, but they do not communicate the disease
to those in attendance upon them or to others in the vicinity. Evidently
some factor essential for the propagation of the disease is absent,
although we have the sick man, his clothing and bedding, and the
insanitary local conditions which have been supposed to constitute an
essential factor.
Pages:
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385