Sessional_Paper_1905 — Page 454

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For the purpose of analysing the relations of rat and human plague I have constructed tables and curves for different districts as given above.

Health District 1-Victoria.

Here we find the tail end of the rat and human plague in 1903 to be almost synchronous. The table shews that from the 35th week, 1903, to 17th week, 1904, only two infected rats were found-one in the 42nd week, 1903, out of 13 rats examined and one in the 7th week, 1904, out of 4 rats examined-giving percentages of 7·7 and 250 respectively.

It is probably, therefore, that during this long period Health District I was very free from rat plague. It is noticeable too how free from human plague it was during the same period.

The epidemic period for 1904 in this district may be considered to have be- gun in the 20th week, just two weeks after the rat plague began to be constant.

The epidemic curve, however, does not rise in a manner corresponding to the rise of the rat curve up to the 23rd week of 1904.

If, however, the 1904 epidemic be considered to have begun with the case in the 16th week, the question of its relation in point of time to the rat plague curve cannot be answered in the same way as no infected rats were known in this dis- trict for 9 weeks previous to this case.

Health District II.

The table and chart shews no infected rats from week 31 to week 40, 1903, while there were four human cases during this period. The rise in the rat curve in the 41st and 42nd weeks, 1903, is accounted for by one rat in each week being reported infected out of a total of nine examined each week.

Four weeks afterwards a plague case was recorded.

The rat curve shews that plague was fairly continuous amongst rats from weeks 3 to 31 of 1904, but no human cases were recorded until the 14th week of 1904.

Four weeks after the rise of this rat curve to its maximum we find the max- imum height of the epidemic curve, but while the rat curve continues at a high percentage on till the 31st week, the epidemic curve ends after the 27th week.