In view of what has thus far been said it is evident that the preventive measures which were formerly relied upon to arrest the epidemic ex. tension of this infectious disease were either of no avail or of comparatively little value. Isolation of the sick from contact with non immune individuals is not necessary, but pro tection of the sick, by mosquito-bars, from the bites of mosquitoes is all-important. Disinfec tion of clothing and bedding is of no avail, but the destruction of infected mosquitoes, by sulphur fumigation or otherwise, is an essential measure of prophylaxis. Street cleaning and municipal sanitation generally have no material effect in preventing the extension of this dis ease, except in so far as they result in destroy ing the larva and breeding places of mosquitoes. Applying the knowledge gained •by Major Reed and his associates in a practical way, as above indicated, the medical officers of the United States army stationed in Cuba have been able to completely eradicate yellow fever from the city of Havana, which had been the principal en demic focus of the disease for many years; and sanitarians feel confident that by the application of the same methods the epidemic extension of the disease within the limits of the United States, or elsewhere, may be entirely prevented. Thus has yellow fever, which formerly ranked with cholera and bubonic plague,— although having a more restricted area of prevalence,— as one of the most fatal scourges of the human race, been robbed of its power for mischief by the painstaking researches of scientific investi gators. The limits of the present article only permit a brief reference to the history of the disease under consideration. It has a compar atively restricted geographic range, hut there is eNery reason to believe that this might be greatly extended if cases of the disease should he introduced to all of the regions where the intermediate host (Stegornyia falciata) of the 'yellow-fever germ' is found. That the dis ease has not been introduced into regions re mote from its principal endemic foci is prob ably due to the comparatively brief duration of the attack, to the fact that the infectious agent is only present in the blood during a brief period (three days) and to the circumstance that it cannot be transmitted in any other way than by inoculation — either directly, as in the experiments of Reed and his associates, or through the medium of an infected mosquito. Epidemics have occurred in the United States at all of our principal seaports on the Gulf of Mexico and on the Atlantic Coast as far north as Boston. It has also invaded many of the Southern States, prevailing as a widespread epidemic in the interior, and has extended up the valley of the Mississippi as far as Saint Louis. It has been epidemic at all the principal seaport cities of the West Indies, of Mexico, of -Central America and of South American countries bordering upon the Gulf of Mexico; also upon the Pacific Coast of Mexico and South America and in the Atlantic-Coast cities of Brazil and also of Argentina. The cities of Havana, Vera Cruz and Rio de Janeiro were long regarded as its principal endemic foci. The climate of these cities is favorable to the survival of the Stegomyia throughout the year. Consequently, when once introduced, the dis ease continued to be propagated through a series of cases, occurring successively without regard to seasons. Thus it was ascertained by the Yellow Fever Commission, of which the writer was a member (1879), that during the 10 years from 1870-79 there was not a single month without some recorded deaths from yellow and this continued to be the case until the disease was eradicated in 1901 by the well directed efforts of Colonel Gorgas, of the medi cal department, United States Army. In his report as sanitary officer of the city of Ha vana for the month of November 1901, he says: •Last year (1900) we had, during this month, 214 cases and 54 deaths. This year the last case of yellow fever occurred on 28 September; that is, we have gone over two months without a single case or death belonging to Havana.' . . . 'This result I consider due to the sys tem, introduced last February, of killing infected mosquitoes in the neighborhood of each point of infection as it developed.' The introduction of yellow fever into the previously healthful city of Havana is recorded by the historian Pczuela, as follows: •Although Havana is situated on the northern boundary of the torrid zone, it was very justly considered one of the most healthy localities on the island before its invasion, in a permanent manner, by the vomit° negro, im ported from Vera Cruz in the summer of 1761. In May there came from Vera Cntz, with mate rials and some prisoners destined for the works on the exterior fortifications of Havana, the men-of-war Reisa and America, which corn nomicated to the neighborhood the epidemic known by the name of vomit° negro. At the end of the following June there were stationed in this fort nine men-of-war, despatched from Cadiz, and sent to the chief of squadron, Don Entienne de Hevia; they brought a reinforce ment of 2,000 men. More than 3,000persons succumbed to the epidemic on this, the first ap pearance of the vomit() • History also records the first introduction of the disease to the city of Rio de Janeiro. The highest medical authorities in Brazil agree that sellow fever was not endemic in the prin cipal seaports of the empire prior to the year 1849, when it was introduced to the city of Bahia by the North American brig Brazil, which sailed from New Orleans, where yellow fever was prevailing, and touched at Havana. Two of the crew of this brig died of yellow fever during her voyage from the latter port to Bahia. Soon after her arrival the disease made its appearance among those who had com municated with the ship. The first case oc curred a few days after the arrival of this brig (3 November). From Bahia the disease was carried to Rio de Janeiro, where during the epidemic season of 1850 it caused a mortality of 4,160.
In regions where the winter temperature is so low as to kill mosquitoes, or render them in active, epidemics of yellow fever terminate upon the occurrence of frost, or of continued cool weather. Under such circumstances the disease is not apt to recur during the succeed ing warm season, except as a result of a fresh importation of a yellow-fever case, from which mosquitoes of the new brood may become in fected. Thus in the United States, even as far south as the city of New Orleans, a recurrence of the disease after its epidemic prevalence .is probably rarely, if ever, due to the survival of infected mosquitoes from the year before. It has been shown, however, by Major Reed, and by others that infected mosquitoes may survive in a warm room for more than two months. Prior to the Civil War yellow fever prevailed almost annually in New Orleans and was generally believed by the residents of that city to be disease of the climate' beyond the control of any preventive measures. Later, un der a more stringent administration. of quaran tine restrictions, such success was attained by the health authorities in preventing the intro duction of cases of the disease, and conse quently of epidemics, that a complete change occurred in public sentiment and it is now gen erally recognized that the introduction of one or more cases from some foreign seaport usually Havana or Vera Cruz—is an essential prerequisite for the development of an epidemic in the city of New Orleans. The years of greatest mortality in this city were: 1847, 2,259; 1853, 7,970; 1854, 2,Q.3; 1855, 2,670; 1858, 3,889; 1867, 3,093; 1878, 4,600.
In 1793 the city of Philadelphia, then a town of about 40,000 inhabitants, suffered a devas tating epidemic, the mortality being about 4,000, or 10 per cent of the population. This city was again visited by the scourge in 1797, but the disease was less extended and less fatal total mortality, 1,300. Philadelphia again suf fered in 1798, the mortality 'being 3,645. The disease also prevailed during this year in more Northern seaport cities, although the mortality was comparatively small except in New York, where the deaths numbered 2,080—Boston 200, Portsmouth 100, New London 81. The disease again prevailed in Boston, Philadelphia, Balti more, Wilmington and Charleston, in the year 1802. Minor epidemics continued to occur almost annually in one or more of our South ern seaport cities until the year 1853, when a fatal and widespread epidemic occurred, in volving considerable areas in the States of Florida, Alabama, Louisiana, Mississippi, Ar kansas and Texas. The epidemic of 1867 was also notable in the annals of this disease, al though the area of prevalence was not so great as in the epidemic of 1853. The disease prevailed extensively in the State of Texas, causing a mortality of 1.150 in the city of Gal veston alone. In Louisiana the city of Not Orleans suffered the heaviest loss (3,093). The next great epidemic within the limits of the United States occurred in 1873. The States of Florida, Alabama, Mississippi, Louisiana and Texas were invaded. The mortality in the city of New Orleans (225) was comparatively rns11. hut Shreveport lost 759 of its irrhabitants, and the disease extended its ravages to Memphis, Tenn., where there was a mortality of about 2,000.
The last great epidemic of yellow fever is the United States occurred in 1878, when 132 towns were invaded in the States of Louisiana, Tennessee, Alabama, Mississippi and Kentucky. The total reported mortality was 15,934, and the number of cases more than 74,000. Yellow fever has never invaded the populous countries of .Asia, which have their own endemic pesti lential maladies. It has been introduced fn.= the West Indies to Spain and to Portugal, but is unknown as an epidemic in other ceentnes of Europe. In Africa it appears to be ende mic on the west coast and some authors beliot that this was the original home of the disease Others contend that it was originally a disease of the West Indies and that its occurrence ‘,t, the African Coast resulted from the importa tion of cases from those islands. The early historians, Herrera, Oviedo, Rochefort and others, make reference to epidemics among the natives which occurred prior to the discos cry of the Antilles, and to fatal pestilential diseases among the first settlers of these islands; btu their accounts are not sufficiently exact to en able us to affirm that the disease referred to by them was yellow fever. The west coast of Africa was discovered and colonized to some extent before the discovery of America, but the authentic accounts of the prevalence of yellow fever on this coast date back only to the year 1778, over two centuries after the first settlements had been established. On the other hand, this very epidemic of 1778 at Saint Lou: (Senegal) was traced to importation from Sierra Leone a portion of the African Coast which, according to Hirsch, "appears to be the headquarters of the disease, and the starting point of its epidemic inroad into the territories lying to the north and south, as well as intc the West African islands.' Rochefort, whose (Histoire naturelle et mo rale des isles Antilles de l'Amerique' was poia lished in Holland in 1558, says of the \1est Indies: "The air of all those islands is temperate and healthy when one is accustomed to it. The poste was formerly unknown there as well as in China and other places in the Orient; but some years since the islands siert afflicted with malignant fevers, which the ph‘ sicians considered contagious. The had air e a• brought there by some ships which came the coast of Africa, but at present we hear nothing more of these maladies." It seems very probable that a pestilent. malady which prevailed for a time. in tha-t usually healthful islands and then was in fact yellow fever, and that it was :ntr duced by ships from the west coast of Atr.,. is not at all incredible. Indeed, it alerso%1 .411" necessary to look for an original endemic its.