Yellow fever never occurs in England, except when imported from the West Indies or other countries in which it is endemic. It clings to seaport towns in hot countries; and as a permanent disease is only found when the mean winter temperature is at least 68°-72° F. A frost always stops an epidemic of this disease. The germs of this disease are communicated by mosquitoes, which act as an intermediate host. Dr. J. W. Lazear, although isolated from yellow fever cases, died of it seven days after submitting to the puncture of an infected mosquito, thus proving the communicability of this disease, and entitling himself to an honoured position among scientific martyrs.
PLAGUE.
Plague is an Eastern disease, which occasionally shows a tendency to become widely epidemic. It is due to a rod-shaped bacterium, averaging ·8 µ to 1·6 µ in length, which does not form spores. In its characteristic form patients suffering from this disease have inflammatary swellings (buboes) of various glands: hence the name Bubonic Plague. In other cases it simulates ordinary pneumonia, typhus or septicaemia; or the patient may be so slightly ill as to be able to walk about. It appears probable that the bacillus enters the body through cracks or other lesions of the skin, possibly also by inhaling infective dust. The rat is an important factor in the spread of plague. Very commonly plague has been widely prevalent and fatal among them before it attacks human beings. Rats also bring it in ships from infected ports. Hence one of the most important preventive measures is to kill all rats on board ship, before the cargo is unloaded. This has been done by sulphurous acid fumigation in the holds. The use of carbonic oxide gas will probably be found practicable for the same purpose. Manson has put the importance of this point tersely as follows: “To prevent cholera the tea-kettle, malaria the mosquito net, and plague the rat-trap.” Flies may carry the infection (page 281). It has been suggested that the fleas of rats carry the infection (page [281]).
ANTHRAX.
Anthrax is a very fatal disease in cattle and sheep, occasionally in pigs. Butchers may inoculate themselves with it when dressing a diseased carcase; the tanners similarly when handling the hide; and woolsorters may inhale it when sorting wool derived from a diseased animal (page [107]). To prevent the latter, suspected wool must be disinfected by steam, and special arrangements made for carrying off the dust produced during sorting.
PUERPERAL FEVER
occurs after childbirth. It is caused like erysipelas by the inoculation of septic material. This may be conveyed by dirty instruments (syringes, etc.), or by dirty hands. Hence the importance of extreme cleanliness of hands, finger-nails, and all articles used during and after childbirth.
RHEUMATIC FEVER
has been commonly attributed to a damp condition of the atmosphere and soil. I have elsewhere shown that this is a mistake, probably arising from the fact that these conditions produce what are called “rheumatic” pains, though they have no true relationship with acute rheumatism (rheumatic fever). I have shown that rheumatic fever occurs chiefly in very dry years, the excess of prevalence in such years being sufficient to justify the use of the term “epidemic.” There is strong reason to believe that rheumatic fever is an infective disease, derived, not from other patients suffering from the same disease, but from some outside micro-organism which is ordinarily saprophytic. It follows the rule that when the lesion produced by an infective disease is deepseated (in the joints in this instance), no infection can be communicated to other persons. Some families are much more prone to rheumatic fever than others.