9

H.—l9b

In 1917 there were 1,156 cases of influenza, fairly evenly distributed throughout the j'.ear, but with a distinct wave in early spring, the crest of which was reached in September. With this fall in influenza incidence there was also a reduction in pneumonia and cerebro-spinal meningitis, only 14 cases of the former being notified, with 1 death, and 13 of meningitis, with 8 deaths. Seven of these cases of cerebro-spinal meningitis occurred in connection with the slight influenzal outbreak in the spring. < The Epidemic of 1918. In 1918 there have been 8,528 cases of influenza all told, with 287 deaths, 280 of which were from pneumonic complications and 9 from cerebro-spinal meningitis, a case mortality of 33 per cent. The accompanying chart shows the annual recrudescence of influenza in the camps.

Note —The spacing above 100 is decreased. This exaggerates the minor waves below 100.

It will be noticed, on referring to the chart, that the waves of the epidemic have hitherto reached their crests in the winter months--July to September—and this is in accordance with experience in Britain. In 1918, however, there were two distinct waves, one reaching its maximum crest in September with fairly gradual rise, while the other arose very suddenly in the latter days of October and spread with remarkable rapidity, reached its crest at the end of the first week in November, and then declined almost as suddenly as it rose. The virulence of this second wave was very much greater than that of the first, since in the latter only 2 deaths occurred among 3,170 cases which were directly attributable to influenza, while there were 281 deaths among the 4,749 cases forming the second wave. The greater number of deaths was due to pneumonic complications, as is usual in influenza, and the remainder were from cerebro-spinal fever, another complication arising where catarrhal diseases are massed together. Primary Wave. —The. primary wave of the epidemic in the camps was not accompanied to any marked extent by pneumonic complications, as only 13 of such cases (5 at Featherston, 2 at Trentham, and 6 at Narrow Neck) occurred between July, when the first wave began, and the 28th October, when the second wave started. Only 1 of these died. There were also some severe influenza! attacks in October with slight lung symptoms, but not definitely pneumonic. It seems possible that the elaborate system of segregation of recruits and inhalation treatment adopted in the camps sufficed to keep these pulmonary complications in check so long as they were of the lower degree of virulence. As regards cerebro-spinal fever the influence of the first wave is more marked. In the first week of July these cases began to appear in Featherston coincident with the rise of influenza. Later a few cases also arose in Trentham, and by the end of October 31 cases had occurred, with 7 deaths in the two camps or in persons associated with the camps. In 7of these cases the patient previously suffered from a definite influenzal attack, but only lof the 7 died. In the remaining cases it is reasonable to assume from our knowledge of cerebro-spinal fever that it was the outcome of the epidemic of influenzal catarrh. This supposition receives support from the fact that carriers of the meningococcus became much more frequent in incoming recruit drafts in the months of August ami September. Apart from the Expeditionary Force camps an outbreak of cerebro-spinal

2—H, 19b.