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In conclusion, the results of the swabbing of a number of the inmates of the Victoria Gaol show: Firstly, that a number (24'61 per cent.) of carriers of organisms indistin- guishable from meningococci have been found. Secondly, that these carriers harbour practically all types of the meningococcus. Thirdly, that three of the carriers harbour organisms indistinguishable from the types of those found in the epidemic. One of these inmates carries almost a pure culture of one of the types prevalent in the epidemic. Fourthly, that the percentage of carriers in gaol is higher than that demonstrated by Drs. Macfarlane and Earle among the actual contacts with the patients during the epidemic. Finally, among the six hundred or more prisoners, no case of epidemic meningitis has developed.
5.--Epidemiological Conclusions.
The epidemiological conclusions from the foregoing findings are as follows:
(a.) The pre-epidemic factors.--Sporadic cases of meningitis have occurred. Car- riers of meningococci have also been found in the gaol population, in some who have been inmates for over a year. On the other hand, the port is a great commercial centre and a carrier or a patient may have been "im- ported". In other event, the source of infection may have been a healthy carrier or a patient, native or foreign.
An excessively dry but extremely cold winter prevailed, at the same time there was an extraordinary number of cases of pharyngitis and bronchial affections and influenza.
These are favourable conditions in view of previous experience for development of cases of epidemic meningitis but these factors do not explain the great spread of the disease throughout the Colony, especially throughout the Chinese community.
(b.) The influence of overcrowding. The factor which impresses one as being of greatest importance in the dissemination of the disease in the Colony is the extensive overcrowding. The bases upon which this conclusion rests
are:-
1. The meteorological conditions.
2. The relative incidence of the disease in crowded and in uncrowded
districts.
3. The lack of relationship between the number of carriers and the spread
of the disease.
4. The bacteriological evidence obtained from the patients.
*
It has been demonstrated that the meteorological factors have an important relation- ship to the dissemination of epidemic meningitis. Cold weather especially in the absence of sunlight resulted in an increase in the number of cases. On the other hand, the meningococcus is........ a fragile micro-organism and does not long withstand ordinary air temperatures and the drying of the secretions containing them; once separated from nasopharynx, it soon succumbs in external nature". But when the cold weather appears the population, already overcrowded abandon the habit of sleeping out in the open streets and literally swarm in the cubicles. These cubicles are box-like compartments, com- pletely shut in the cold nights, unventilated and overcrowded.
Should one inmate harbour the meningococcus it will soon be distributed over all the others of the dwelling. The mechanism of dissemination is more or less direct; it.... consists in the ejection of the nasopharyngeal secretions into the surrounding atmosphere. This ejection does not take place during ordinary breathing and little, as a rule during quiet speaking. But in loud speaking and particularly in coughing, sneezing, hawking and spitting, the secretions may be sprayed and scattered widely" (ibid).
Thus while the meningococcus is a very fragile organism and succumbs easily in external nature, in overcrowded and ill-ventilated conditions it passes from one to another readily. The cold temperatures, while detrimental to the meningococcus out- side the body, by bringing about a condition of overcrowding and close contact, favors the general distribution of this micro-organism.
* Flexner, Simous Mode of Infection, Means of Prevention and Specific Treatment of Epidemic Meningitis, New York, 1917.