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and attendants on such cases have to exercise the greatest precautionary measures possible. Convalescent cases must be kept isolated until all plague bacilli have disappeared from the sputum.
It has already been mentioned that as a general rule all cases of plague ought to be isolated. No exception to this rule can for a moment be entertained in regard to primary pneumonic plague. In dealing, however, with the disease as met with here in Hongkong, namely, the septicemic form with its bubonic manifestations, the question of isolation need not be so rigidly enforced. The possibility of the spread of infection from these cases is limited to the excretions and secretions from the patients, and in any well regulated Hospital, where the thorough disinfection of such discharges can be carried out, the treatment of such septicemic cases of plague can be as sucessfully accomplished as the treatment of severe cases of enteric fever.
Further, of great importance is the supervision of the relatives and friends of all cases of plague. The isolation of contacts is of the highest importance.
No plague stricker city can be said to have its sanitary arrangements complete, unless ample provision has been made for the provision of segregation camps.
Probably the most important part of the campaign against plague is that directed against rat plague. Were man the only means of harbouring plague, there is little doubt of our soon gaining complete mastery over spread of the disense. The results obtained by thorough disinfection of houses, have clearly shown this to be true. Yet, notwithstanding the non-occurrence of further cases of plague in these houses disinfected, fresh cases in the immediate neighbourhood occurred. This fact, coupled with our knowledge of the part played by infected rats, has led to a modification in our cleansing and disinfecting system. Now-a-days, if plague is to be stamped out, thorough disinfection, cleansing, and destruction of rats of whole districts must be undertaken. The methods as applied to single houses or units would appear to be of no value. The generalised disinfection and cleansing, strongly recommended by Sir HORACE PINCHING, has given excellent results in the hands of GoTSCHLICH, BITTER and others.
So far as rat plaque is concerned, it would appear that this form is mainly responsible for the bridging over of the various epidemics of the disease in man.
The clinging of plague to one particular spot, and its periodical re-appearance, mostly at definite times of the year and at the season of the year when rats are most prolific. points to the fact that the disease is maintained in the body of the rat. My own res arches show the pr. sence of rat plaue thoughout the whole year. Plague in man in Hongkong is only present in epidemic forin during certain seasons of the year.
I am convinced that the rat harbours the disease in a chronic or latent form, which continues until the season when rats are ver、 prolific. At this period, the disease again becomes virulent through the bodies of young rats. The rat epide- mic and mortality assume greater proportions and sooner or later the disease breaks out in man.
That plague may be chronic and latent in rats, the virus being maintained for several seasons, has been experimentally shown by the laboratory experiments of KOLLE and MARTINI (Dent. Med. Woch. Nos. 1-4, 1902). They are strongly supported by GoTSCHLICH, and it is our intention to verify these results if possible in Hongkong.
In previously non-infected districts, rat plague usually appears in advance of human plague. In endemic areas, where rat plague is constantly present, the increase in fie rat epidemic appears in advance of plague in man.
It must not be forgotten that rat plague may exist for an indefinite period without the disease appearing in man. This fact is of importance to sea port towns. In such towns human plague may not have made its appearance. yet plague may exist amongst the rats. The orensional systematic examination of the rats of such cities or towns would appear to be of value. The recognition of the disease in rats, previous to its appearance in man, would simplify the prophylaxis to an extreme degree.