Sessional_Paper_1904 — Page 753

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The History of the Course and Relations of Epizootic and Epidemic Plague in the Health Districts of

Hongkong during the year 1903.

In dealing with the subject of rat and human plague for the year 1903, the descriptions of the epizootic and the epidemic merely require to be touched. The details given under the History of the 1903 outbreak conform more or less to those found during 1902.

Much greater reliance is to be placed upon these results. The observations were made after the system of rat collection and examination had been more or less perfected. Certain errors which were brought to light during the year have been eliminated as far as possible. These are, mainly, the possible importation of dead and living rats into the Colony by the Chinese who evidently believed that fortunes were about to be amassed by the sale of rats to innocent coolies at the expense of the Government. This factor in the system of rat collection was fortunately soon discovered and rigorously dealt with by the Sanitary Authorities.

In the preparation of the curves for 1903, this falsifying of the rat return has been remedied as far as possible. It would not appear to have altered the condition of affairs to any great extent as can be seen by comparing the charts with those of 1902.

A factor in determining the relationship of epidemic plague to the epizootic was noted in the resumé for 1902, namely, the number of cases of both outbreaks at one's disposal. Obviously the epidemic of 1902 occasionally failed me in producing a sufficient number of plague cases in certain districts in the epidemic of 1903. On the other hand, the epizootic exceeds the epidemic in number of cases- so greatly that, in certain charts, it is difficult to trace much connection between the curves.

Comparisons made with the charts of 1902 will clarify matters considerably. Again the charts for 1903 have in their favour the determination of the amounts of both epizootic and epidemic throughout the whole year.

There are many points of considerable importance in regard to the behaviour of the epizootic during the interval between two epidemics. The influences exerted by the epizootic in determining the amount and the distribution of the succeeding epidemic, etc., are discussed under a separate heading.

The charts are prepared in the same inauner as those for 1902. They are in certain instances much more extensive, but this is acconuted for by the increased severity of the epizootic and epidemic throughout the year. Attempts were made to reduce the charts, but the result was found unsatisfactory and might possibly lead to certain misinterpretation.

In preparing all the charts, actual numbers have been dealt with.

During the year, 101,056 rats were examined. Of there, 3,744 were found to be infected with plague.

General Resumé of the Results obtained during 1903. The results obtained during this year are more regular. Some of the greater oscillations in the curve of the epizootic about its maximum are in all probability due to the fraudulent import of rats which was rampant during the height of the plague season. can be more or less eliminated in comparing the results.

These

Similar to what was obtained in 1902, sudden variations in the rat content and number of plague infected rats in each district, are found.

Of importance in regard to the early appearance of the epidemic is the presence of a considerable amount of rat plague on the 1st of January. So long

So long as this epizootic_maintains its average degree of severity, no cases of human plague are found. Immediately, however, a definite rise of rat plague takes place, cases of plague in man may be expected within a fortnight.