AGATIHN of DISEASE By.) nee the tion of the true etiology of yellow fever, and the institution of sanitary reforms in Cuba based on this knowledge, the disease has eomplet4 disappeared from that island. Its occurrence in hot and moist areas and at low levels coincides with the distribution of the mosquito. It is more fatal in the summer months, from 'Nay to August, and is stopped by the onset of frost. All ages and both sexes are equally affected under like conditions of exposure, hut negroes are less susceptible than whites. One attack confers im munity against others.
Attempts to discover the causative germ of yellow fever (if one exists) have been unre mitting. Different observers have claimed to have found a bacillus which is constantly pres ent, and the fact that a definite time (twelve days) elapses between infection of the mosquito and the development of its power to communicate the disease to man, points to a germ as the agent. Careful experiments and investigations, however, by the United States Army Commission in Cuba show that no bacterium or protozoan of any kind is present in the blood tissues or excreta of yel low-fever patients: that their blood is capable, when injected into healthy persons, of communi cating the disease: and that the serum of the blood, when separated, is also infective. The conclusions are that the specifie agent is in the serum. and that it is either ultra-mieroscopic or it is non-lciett.rial and probably a toxin.
The period intervening between infection and (lie onset of the disease is as a rule three or four days. but may be from one to seven days. The attack may come on suddenly with severe chills or rigors or may lie preceded by symp loins of languor, headache. and malaria. The temperature rapidly rises and in two or three days may reach 105° P. or even higher. The fever lasts from three to live days and is at tended by pains in the back, limbs, and head. The tongue is coated but bright red at the tip and sides; there is tenderness and pain over the epigastrium, with nausea and vomiting. About the second or third day jaundice begins in the conjunctivas, and quickly spreads over the whole body. In favorable eases the fever abates at the end of the fourth or fifth day, and recovery is complete in two or three weeks. But in severe cases the symptoms continue with increased vio lence. The skin becomes yellower, small hemor rhages take place into the skin, and vomiting becomes frequent. The rejected material is at
first light in color (`white vomit:), but is soon followed by the 'black vomit,' which is rightly considered an ominous symptom, since it be tokens an extensive alteration in the blood. Black vomit has somewhat the appearance of coffee grounds, and consists of blood which has been extravasated into the stomach and further altered by the action of the gastric juice. Blood may also be discharged from the bowels and hemorrhages take place from the nose, month, or gums. At this stage delirium is apt to set in and the patient soon lapses into unconsciousness. In very violent cases death sometimes takes place within a few hours of the onset of the first symptoms. In these cases jaundice and high temperature are absent. Death is due to hemor rhage, cardiac failure, suppression of the urine, or to the direct effect of the poison on the vital centres. The mortality in different epidemics varies greatly and may be as low as 10 per cent. or as high as S5 per cent. of the individuals at tacked. Among alcoholic patients and those who are weakened from hardship or other causes the death rate is exceedingly high, as it is also among unacclimatized persons.
The solution of the problem of preventing out breaks of yellow fever is one of the most recent and remarkable achievements of sanitary science. The disease is known to he favored by heat, moisture, bad drainage, house and communal un cleanness, and generally unhygienic conditions, and these must be remedied as a first step in stamping out the malady. Chief attention, how ever, is paid to the mosquito, and its breeding places should be destroyed. During an epidemic the greatest care is exercised to prevent yellow fever patients from being bitten by mosquitoes; special pains are taken to disinfect houses and rooms in which a ease has occurred and to kill all mosquitoes in them. People residing in in fected districts should be careful to guard against being bitten by these insects, both indoors and out. It is proposed to inclose patients suffering with yellow fever in large wire cages with meshes so fine that mosquitoes cannot penetrate them. It is customary to enforce a strict quarantine against vessels sailing from ports where it is known that yellow fever exists. ( See QUARAN