The nature and control of yellow fever / by Harald Seidelin.

  • Seidelin, Harald.
Date:
1913
Catalogue details

Licence: Public Domain Mark

Credit: The nature and control of yellow fever / by Harald Seidelin. Source: Wellcome Collection.

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    that they were not at all uncommon in the Canal Zone. This should not be so; the careful vigilance should be kept up, as long as there is any possibility of reintroduction of infection. This possibility not only exists, but is abundantly present. We should be cautious and not feel secure too early; the history of epidemics teaches the lesson that the great infectious diseases are subject to oscillations, on which even the most radical measures have little influence. To give an idea of the actual prevalence of yellow fever, I shall only mention that 716 deaths were officially reported in 1910 and 488 in 1911; in the first six months of 1912 there have already been about 500 deaths. There is little doubt that these figures represent a minimum. In the Yellow Fever Bureau Bulletin we completely abstain from summing up the cases reported, as it is common know]l- edge that the reports of cases are much more incomplete than those of deaths. and from some places the reports give only the number of deaths. If we calculate a mortality of about 20 per cent, then there would have occurred about 2,000 cases of yellow fever in the first six months of this year. This figure would include only compara- tively typical cases which could be recognized clinically without much difficulty; if quite mild and atypical cases were included, the mortality would probably not attain 20 per cent. One of the most important points in the epidemiology of yellow fever is the existence of unrecognized and unrecognizable cases. It is the experience of nearly all observers that yellow fever may pre- sent all degrees of intensity from severe, fatal cases to mild, atypical attacks of very short duration. Cases belonging to the second group are not uncommon. Their importance for epidemiological questions is obvious. It is asserted by both ancient and modern observers that the susceptibility of an individual diminishes with the length of time during which he has resided in a yellow-fever-infected country. This phenomenon we are entirely unable to explain, if we do not admit that the (relative or absolute) immunity has developed as a consequence of acquired infection. This matter is very clear, and will be universally agreed to, I believe, as long as we deal with foreigners. But when the same consideration is extended to natives opposition is often met with. Nothing, however, can be more clear. If an individual is immune to yellow fever, it is reasonable to conclude that he has already gone through at least one attack of the disease. When the immunity is considered in this way, we can form a definite idea of epidemiology. Yellow fever is endemic in certain areas, at present in several parts of Mexico, Brazil, Central America, and Ecuador, and in the Old World in West Africa. The infection is continuously maintained in a mild form in those countries, but
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