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Medical Officer of the Port, Dr. Macfarlane, the Government Bacteriologist, and Dr. Gale, the Medical Officer of Health. The epidemic was not severe in its effect, but the distri- bution of these ailments was quite general. On the other hand there is no evidence of any great increase in measles at this time nor mumps. Besides the prevalence of sore throat and influenza the health conditions of Hongkong was relatively good.
(f) Migration of the population.--Migration may be an important element in the dissemination of the disease as well as in the recurrence or continuance of an epidemic. As for the first, namely, the dissemination of epidemic meningitis, there occurred in the ports of Swatow, Shanghai, Kobe, Osaka and Tokyo an extraordinary number of cases (and in most instances were recorded for the first time). These cities are along the main lines of travel out from Hongkong. The cases occurred a few weeks after the outbreak at Hongkong. For example, at Swatow about 60 cases developed during March. The Hongkong Blue Book for 1916 and 1917 places the emigration from Hong- kong at 117,653 and 96,298 respectively.
On the other hand the question of recurrence or continuation of an epidemic is related in a degree to the immigration. The immigration into the Colony for 1916 was 72,405 and for 1917, 98,232. The figures for 1918 are of course, not available. * It has been pointed out that the entrance of a new susceptible element of popula- tion from a non-infected district into the epidemic area of the Colony, and this new element, usually coolies, existing in close contact with the disease, will tend to increase the number of cases. Or they will cause a disturbance of the insusceptible ratio of the normal native population and when the cold season approaches, or under other conditions favourable to the spread of epidemic meningitis, there will be new soil for an outbreak.
(g) Geographical distribution of cases. It is of interest to note that while it was of rare occurrence that more than one member of a family was afflicted, yet the disease showed its greatest number of cases in limited areas. One area is included by D'Aguilar Street on the east: Pokfulam Road on the west: Caine Road and High Street on the south and the Harbour on the north. In this area, the section bounded by Eastern and Western Streets notably overcrowded, is particularly remarkable with regard to the number of cases yielded. In Eastern Hongkong, the section between St. Francis Street and Wanchai Road, Queen's Road and the Harbour yielded the greatest number of patients. In the Kowloon Peninsula, the districts of Yaumati and adjacent Mong Kok Tsui and Hung Hom showed the greatest incidence of the disease.
All these districts correspond to the most crowded sections of Hongkong and Kow- loon. In areas where there is no crowding, notably the Tsim Sha Tsui, and the Hill District, there were none or comparatively very few cases developed.
(h) The overcrowling of the population.-As the disease was limited to a great degree in the overcrowded sections, it is important to investigate this phase of the epidemiology of epidemic meningitis.
In
Three causes operate to effect overcrowding. In the first place there are too many houses on too small a space, in this way causing structures to be in close proximity. turn this gives rise to insufficient ventilation and for the most part very little light. The areaways and the streets or lanes are so narrow and the houses are so high (in proportion to the narrowness of the street) that not only ventilation and light becomes deficient but the air is always damp from wetness of the passageways. They are never thoroughly dry, possibly from the position of the Chinese community, namely, at the foot of the Hills where the water from the higher attitudes is continually settling.
In the second place, there are no arrangements for veutilation within the house. A typical example may be cited.
On June 7th, 1918, through the courtesy of Mr. Adam Gibson, Head of the Sanitary Department, I was permitted to make an inspection of No. 15, Chinese Street. This was done at about 11 p.m. I was accompanied by Inspector R. R. Wood of the Sanitary
These figures are official returns. The actual number of Chinese leaving or entering the Colony is probably much greater. While the travel on most junks, all steamships, and railways can be determined it is impossible to account for small junks and sampans. The same proportion of immigration, however, is probably maintained in 1918.