YELLOW FEVER is a typhus-like fever of certain ports, or of ships hailing from them. It differs from all existing types of fevers and infections in largely sparing the Negro. It resembles cholera in being endemic in some parts of the world (but only shipping places) and in being importable to others, in being an infection that issues from the soil or some medium equi-valent thereto, and in being a virulent filth-disease; but it differs from cholera in having at the outset a violent febrile paroxysm lasting two or three days. As a fever it resembles typhus; but it differs from typhus in all those "exogenous" characters wherein it resembles cholera. The generic place and affinities of yellow fever are perhaps best provided for in the nosology of Cullen : the symptoms are within the sphere of the organic nervous system; they stand for excitement first and prostration afterwards; and they are an effect of human effluvia. Its differentia among the " nervous " fevers due to " human effluvia " would be its maritime or amphibious habitat, its associa-tion with tropical heat, the chief part played by the liver in its symptomatology (on the lines of acute yellow atrophy), and the singular immunity of the Negro race.
An attack of yellow fever may follow definite exposure Charac-(such as landing at an endemic port) within a few hours, teristics. as in corresponding cases of cholera; but the outbreak of symptoms is more often delayed for a few days, the limit of "incubation" being about eight. The few hours' languor, chilliness, headache, and muscular pains, which might be the precursors of any febrile attack, are followed by a peculiar look of the eyes and face, which is charac-teristic : the face is flushed, and the eyes suffused at first and then congested or ferrety, the nostrils and lips red, and the tongue scarlet,—these being the most obvious signs of universal congestion of the skin, mucous membranes, and organs. Meanwhile the temperature has risen to fever heat, and may reach a very high figure (maximum of 110° Fahr., it is said); the pulse is quick, strong, and full, but may not keep up in these characters with the high temperature throughout. There are all the usual accompaniments of high fever, including hot skin, failure of appetite, thirst, nausea, restlessness, and delirium (which may or may not be violent); albumen will nearly always be found in the urine. The fever is a continued one so long as it lasts; but the febrile excitement comes to an end after two or three days. In a certain class of ambulatory or masked cases the febrile reaction may never come out, and the shock of the infection after a brief interval may lead unexpectedly and directly to prostration and death. The cessation of the paroxysm makes the stadium, or lull, characteristic of yellow fever. The hitherto militant or violent symptoms cease, and prostration or collapse ensues. The internal heat falls below the normal; the action of the heart (pulse) becomes slow and feeble, the skin cold and of a lemon-yellow tint, the act of vomiting effortless, like that of an infant, the first vomit being clear fluid, but afterwards black from an admixture of blood. It is at this period that the prospect of recovery or of a fatal issue declares itself. The prostration following the paroxysm of fever may be no more than the weakness of commencing recovery, with copious flow of urine, which even then is very dark-coloured from the presence of blood. The prostration will be all the more profound according to the height reached by the temperature during the acute paroxysm. Much blood in the vomit and in the stools, together with all other haemorrhagic signs,-is of evil omen. Constant hiccough, with loud cries or wailing, is a certain sign of 'death, which may also be ushered in by suppression of urine, coma, and convulsions, or by fainting from failure at the heart. The proportion of recoveries is usually less than one-half; but it has been now and then very large (as in the New Orleans epidemic of 1878). Convalescence is on the whole rapid; but, if some old disease, such as ague, have been lighted up, or abscesses induced, it may go on slowly for months. One attack of yellow fever confers a high degree of immunity from a second.
The treatment of yellow fever has been one of the classical subjects of controversy. In the Philadelphia epidemics of the end of the 18th century, Rush gained much credit for his incessant labours in bleeding the victims during the violence of the paroxysm. Al-though blood-letting to relieve the congestions has been given up, experience still favours the resort to vigorous measures at the out-Bet. The following practice was adopted with much success by Dr Joseph Jones during the epidemic of 1878 at New Orleans,—an emetic of ipecacuanha, followed by a powder of calomel (10 to 20 grains), with as much quinine added (the latter ingredient of doubt-ful utility), and that again followed by a full dose of castor oil. Beyond that heroic medication at the outset of the febrile paroxysm, the treatment was directed to assisting the action of the skin and kidneys, by keeping the temperature of the room uniform, by mustard foot-baths, and by copious draughts of lemonade or other aerated water, or of barley water. The diet indicated is fever diet: i.e., it should exclude solid food. For such symptoms as tender-ness over the stomach a mustard poultice is applied; for diminished secretion of urine, dry cupping over the loins. When the lull occurs, the patient should on no account be allowed to get up, as sudden failure of the heart is apt to follow exertion. Iced cham-pagne and beef-tea are found to be the best supports for this stage. The only thing to do when black vomit threatens is to give the patient ice to suck, or (more questionably) to place an ice-bag on the abdomen. When the stage of prostration assumes a "typhoid" character, an enema of ice-cold water, with a little turpentine in it, helps to get rid of the flatus and to stimulate the kidneys. Re-covery is in all cases more probable where there is abundant cubic space and good ventilation. Patho- Yellow fever is of the nature of typhus, in the language of logy. older writers, a nervous or putrid fever. The two salient things about it are the internal haemorrhages and the almost complete arrest of the function of the liver ; of these the latter would seem to be primary and the former secondary. The state of the liver on examination after death from yellow fever is by far the most significant feature in the morbid anatomy: the bile-ducts and gall-bladder are empty, or contain only a clear albuminoid fluid ; the organ is bloodless and of a golden yellow colour; and the hepatic cells are everywhere full of fatty granules or other molecular detritus. It shows, in fact, the morbid anatomy of acute yellow atrophy, or that state of the hepatic structure and functions which is due to total inhibition or arrest (see PATHOLOGY, vol. xviii. p. 3S6), whether the inhibiting influence be phosphorus poisoning, or emotional strain, or something in the pregnant state, or the infective influ-ence of yellow fever. All the other phenomena of this fever are grouped around the liver derangement, as around a centre, namely, the yellow tint of the skin, the fatty degeneration of the heart favouring syncope, the haemorrhages from the mucous membranes (including the black vomit), the degeneration of the renal epithe-lium with albuminuria, and the coma and convulsions. Yellow fever therefore may be styled a sudden or arbitrary infection im-posed from without, the distinctive mark or "note" of which is the same peculiar group of symptoms that is found in the rare and sporadic cases of yellow atrophy. To reach the full and correct doctrine of yellow fever, we have to harmonize the clinical and pathological facts of the disease, as already given, with the histori-cal, geographical, racial, and other associated circumstances now to be stated.
History The first authentic account of yellow fever comes from Bridge-and geo- town, Barbados, in 1647, where it was recognized as a "nova graphical pestis," that was unaccountable in its origin, except that Ligon, distribu- the historian of the colony, who was then on the spot, connected it tion. with the arrival of ships. It was the same new pestilence that Dutertre, writing in 1667, described as having occurred in the French colony of Guadeloupe in 1635 and 1640 ; it recurred at Guadeloupe in 1648, and broke out in a peculiarly disastrous form at St Kitt's the same year, and again in 1652 ; in 1655 it was at. Port Royal, Jamaica; and from those years onwards it became familiar at many harbours in the West Indies and Spanish Main, and in the Atlantic ports of the British American colonies. It _ is a question whether it had not occurred at Porto Rico, San Domingo, and other places in the Spanish Antilles a good many years before ; but the reports from the colonies of New Spain, both for that and subsequent periods, are highly defective as regards the data needed to distinguish yellow fever from the bilious remittent form of malarial fever, which is a non-infective sickness. The Mexican form of typhus, called " matlazahuatl," which has been an indigenous disease of the native population in the interior for several centuries, has no other connexion with yellow fever than that it belongs to the same family of typhus ; its circumstances are quite different, especially in respect that it is a purely inland form of febris pauperum. In 1853 yellow fever appeared for the first time at Callao and Lima in Peru; and almost in the same months a severe epidemic prevailed among the plantation hands in the sierra region of the interior. The two forms were described as the same disease by Dr Archibald Smith ; but the fever of the sierras was afterwards shown to be a form of typhus, analogous to the native Mexican form, and quite unconnected with the yellow fever of the coast.
In the harbours of the American colonies (United States) the history of yellow fever has been as follows. It begins to be heard of at Charleston in 1693, and at Philadelphia the same year. The South Carolina port has the fullest record of it, next in order in the earlier period being Philadelphia, New York, and Norfolk (Va.). Towards the end of the 18th century the ports of New England, as far north as New Hampshire, have visitations, and it begins to be quite common at Baltimore, Wilmington, Savannah, and New Orleans. At a still later period (within the 19th century) we find the centre of incidence shifting so as to include Mobile, Memphis, Natchez, St Francisville, and Baton Rouge ; and in the most recent period outbreaks are recorded at Galveston and other ports of Texas, and at Pensacola, Vicksburg, and Key West. The Atlantic ports gradually lost it and the Gulf ports took up the inheritance, several of them keeping it still. Some of the epidemics were very disastrous, one of the Philadelphia outbreaks corresponding to the pestilence which figures in the last section of Longfellow's Evangeline: "Wealth had no power to bribe, nor beauty to charm the oppressor." In the New Orleans epidemic of 1878 the deaths num-bered 4056. The American ports mentioned have been only its principal seats, many other smaller harbours having had outbreaks now and then, such as New Haven (Conn.), Providence (R.I.), Swedesborough (N.J.), Alexandria (Va.), Augusta (Ga.), St Augus-tine (Fia.), Opelousas (La.), and Houston (Tex.).
Along with the harbours and anchorages of the West Indies and Spanish Main, the three chief harbours of Guiana (Cayenne, Suri-nam, and Demerara) have had an equal share, and for almost the same period. But for Brazilian ports there is no record of yellow fever until 1849, when it appeared for the first time at Rio de Janeiro, Bahia, and other places. These ports became endemic seats of the infection from that year, and are now more distinctively the head-quarters of the disease than its old West Indian and Mexican Gulf centres. Monte Video had a disastrous epidemic in 1857, and Buenos Ayres a visitation in 1S58 ; but the shipping places of the river Plate are not in the same class of endemic foci as the harbours of Brazil.
There have been a few epidemics at trading places on the West Coast of Africa, most of them subsequent to 1820, and all of them confined generally to white residents.
During the great period of yellow fever (1793-1805), and for some years afterwards, the disease found its way time after time to various ports of Spain. Cadiz, indeed, suffered five epidemics in the 18th century, Malaga one, and Lisbon one ; but from 1800 down to 1821 the disease assumed much more alarming proportions, Cadiz being still its chief seat, while Seville, Malaga, Cartagena, Barce-lona, Palma, Gibraltar, and other shipping places suffered severely, as well as some of the country districts nearest to the ports. These Spanish outbreaks were clearly connected with the ar-rival of ships, but for the most part there had not been cases of yellow fever on board the ships. The last severe epidemic on Spanish soil was at Barcelona in the summer of 1821, when 5000 persons died. The most recent disastrous epidemic in Europe was at Lisbon in 1857, when upwards of 6000 died in a few weeks. The outbreaks at St Nazaire (1861), Leghorn, Swansea (1864), and Southampton have been carefully studied, but are otherwise of minor importance.
Yellow fever is dependent upon high summer temperature for its Special epidemic development, and it requires a good deal of heat to continue local and even after it has once acquired epidemic intensity. In its endemic racial centres in the New World it clings peculiarly to the lower quarters cireum-of the seaports, to the alluvial foreshores, and to the anchorages ; stances, on many occasions it has been prevalent among the crews of men-of-war and of merchantmen at anchor, or moored in the harbour, or lying up in the carénage, when there has been none of it among the residents ashore. It is admitted that the endemic influence which causes it is effluvial or miasmatic from the harbour mud, or from the bilge-water of a ship that had lain in the harbour, or from the alluvial foundations of houses nearest to the beach. So far as prevalence on shore is concerned, it seems to follow the same laws . as cholera and typhoid fever : that is to say, it is an exogenous or soil infection, a fermentation of filth in the ground, with a seasonal activity closely following the movements of the subsoil water. In like manner, when it has been imported to Spain, it has clung to alluvial soil and has spread after the fashion of a soil-borne infec-tion rather than by personal contagion, although in Spanish ports, just as in Philadelphia, according to Rush's opinion, contagious-ness has been found to be " contingent " to it under certain circum-stances. To establish an epidemic in a distant port, it has been necessary that there should be carried thither a material quantity of the specifically poisonous harbour-filth in a ship's bilges, and that the conditions favourable to its increase and diffusion by fer-mentation should exist in the new soil.
The next most significant thing in the incidence of this fever is that new arrivals at an indigenous centre are peculiarly liable to take it, and most liable of all the sailors and others from northern latitudes, such as Sweden, Finland, Holland, and Germany. In fact an epidemic outburst in a yellow-fever port or endemic centre at the present day is commonly connected vrith an unusual influx of strangers. It is not to be supposed, however, that the residents acquire immunity by acclimatization : they have no greater im-munity in that sense than have the Bengalis from cholera, or than those who permanently reside in unsanitary localities from typhoid fever or diphtheria. The only immunity is that of the Negro race, an immunity all the more striking that the Negroes in yellow-fever ports are mostly found living in the favourite haunts of the disease, and that their race is peculiarly liable to all other infec-tions of the kind, including cholera, typhus, and typhoid. Al-though the protection of the Negro of pure blood is not absolute, it is nearly so. In ordinary circumstances Negroes become liable when of mixed blood, and almost exactly in proportion to the degree of white stock in their breeding. These racial peculiarities have been so often remarked and are so universally admitted in their broad significance that no detailed proofs need be adduced. It may be stated, however, that all African Negroes, whether fresh from Africa or long acclimatized to the New World, have the same natural protection ; thus the Nubian regiment in the French ser-vice during the Mexican expedition did not lose a single man, and did not even have a single case, in the epidemic at Vera Cruz in 1866. The protection is profoundly racial, and not due to the Negroes being inured to yellow-fever localities. There is no other instance of the same racial immunity in the whole range of in-fective sickness.
Theory Two things stand out prominently in the foregoing recital of of the facts,—(1) that yellow fever, in time and place, has dogged the disease, steps of the African slave trade, and (2) that the African Negro has a very large racial immunity from yellow fever. The first of these facts was generalized by Audouard (Paris, 1825), but has been neglected and forgotten ; the second fact, which no one seriously disputes, is the complement and confirmation of the historical and geographical induction. The circumstances in Peru, although ap-parently in contradiction, are really corroborative : a form of yellow fever established itself at certain ports of that country in the wake of a notorious Chinese coolie trade (see COOLIE, vol. vi. p. 334) ; but the Chinese themselves were exempt from the fever at the time, and would appear not to have suffered from it in thé subsequent epidemics on the Peruvian coast. The question thus arises as to the particular connexion between the African slave trade (or the analogous Chinese coolie trade) and yellow fever. The first point is that the fever has not been a fever of the voyage but of the land-ing place, although there are several authentic instances [e.g., cases of the "Regalia" and "La Pique") of yellow fever arising at sea from the exposure of white men to the stench of a shipful of Negroes. Again, the filthy condition of a Guineaman on her arrival from Africa was a notorious fact ; and the filth of that kind was discharged into the creeks, carénages, and anchorages of slave ports in material quantity year after year for a long period. At Havana as many as a hundred slavers would arrive in one year. Steady accretions of the filth of slave-ships from the beginning of the traffic to America down to its abolition in 1808, and its final cessation previous to 1860, would account for a peculiarly pestiferous state of the harbour mud, of the beach, and even of the water ; in fact, the water in the Bay of Havana was pestiferous and full of organic matter where it was several fathoms deep, and there was a standing order in the British navy against admitting it into ships. Wher-ever the harbours were most tideless, as around the Gulf of Mexico and in the West Indian Islands, and wherever the soil was most aUuvial, and the movements of the ground-water most extensive, the specific putrefaction or fermentation thus introduced into the harbour would spread farthest on shore, being aided or encouraged always by the abundance of other organic matter which it met with at particular spots, such as the foundations of houses.
The next step is to consider the connexion between this wholesale befouling of slave ports and the particular type of endemic disease. One of the points most emphasized by Audouard was the funda-mental physiological differences between the African Negro race and the white. The discharges of the Negro body might become by their effluvia specifically poisonous, he argued, to white men under special circumstances. A more direct factor in the œtiology was the very common, if not uniform, prevalence of dysentery and diarrhoea in the passage from the Guinea coast to the western shores of the Atlantic : the filth in a slave-ship's bilges was, in part at least, dysenteric in its source and properties. Now, there is much independent evidence, collected from times of war and famine, to prove a certain correlation or equivalence between dysentery and typhus ; according to Blane's phrase, the one was vicarious to the other. Yellow fever is admittedly a form of typhus, a form distin-guished by a hsemorrhagic tendency. Thus we find the connexion explained between dysenteric and other evacuations of the Negro race, carried to the mud and alluvial soil of ports under very peculiar circumstances, and a special form of endemic typhus, dif-fering from the ordinary form in being earth-borne instead of airborne. The remaining part of the synthesis concerns the differen-tial type of yellow fever within the genus " typhus : " Whence did it obtain the " note " or distinctive mark, anatomical and clinical, of an acute yellow atrophy of the liver ? The dysenteric filth that was imported into the harbours of the New World represented that almost unique unwholesomeness of life wdiich is summed up in the phrase "horrors of the middle passage." Among such horrors nostalgia, despair, and the sense of wrong were not the least ; and these are among the states of human feeling that have been known, now and then, in the ordinary way of life to assume that peculiar visceral embodiment, or to find that means of expression, which amounts to acute yellow atrophy of the liver, and stands, in fact, for a total arrest of the hepatic functions, biliary and other.
There is no other theory of yellow fever to contest the field with the slave-trade hypothesis ; that alone satisfies all the conditions of a correct synthesis—historical, geographical, ethnological, physio-logical, and, some would say, even ethical. There have been, various other theories put forward from time to time, all of them much too fragmentary, and therefore erroneous, such as the hypo-thesis of rotting timber (in wharves, ships' hulls, kc), of sugar cargoes, of common foul bilge-water, of madrepores, and of bacilli. The bacillary or parasitic hypothesis is the fashionable one at present, but it is much too ambitious, as ordinarily held, and altogether wide of the mark. The part played by putrefactive organisms is a subordinate one. In the general grouping of factors they can only come in after we have found the specific integral of the yellow-fever soil in its endemic seats ; they cannot elaborate the miasmatic poison of yellow fever without a definite pabulum, any more than the " lactic bacillus " can produce lactic fermentation without milk-sugar.
The sanitary or public health aspects of yellow fever have been discussed in great part under QUARANTINE (vol. xx. p. 156). In regard to its sanitation at the endemic seats in the West Indies, Guiana, Brazil, Central America, and the Gulf States of the American Union, the same principles apply as to other filth-diseases. The object is to secure a clean soil, and to that end drainage and sewer-age serve best. In the sanitation of yellow fever the case is so far peculiar that the harbour bottom, the adjoining mudbanks and mangrove swamps, and even the seawater itself, are apt to retain the specific taint, especially where the cleansing action of the tides is slight. But there is good reason to think that the specific taint in the soil is everywhere slowly disappearing, now that it is no longer reinforced by fresh supplies year after year. It has practically vanished from the Atlantic ports of the United States, and has be-come almost rare in such harbours as Port Royal, Jamaica. Its headquarters are now the Brazilian ports, which were the last to develop it (in 1849).
Literature.—The chief work is that of La Roche, Yellow Fever, 2 vols.,
Philadelphia, 1855. A very full bibliography is given by Hirsch at the end of
his section on "Yellow Fever," in Historisch-Ceographlsche Pathologie, vol. i.,
Stuttgart, 1881 (Engl, transi, by Creighton, London, 1883), Recent experience,
epidemiological and clinical, is given in the writings (2 vols.) of Dr Joseph
Jones of New Orleans, 1887 ; see also Maclean's Diseases of Tropical Climates,
London, 1886. Among the numerous monographs may be specially mentioned
these of Pym (Observations upon the Bulam Fever, London, 1815), who showed
that one attack gave immunity, and of Daniel Blair (Some Account of the Last
Yellow Fever Epidemic of British Guiana, with plates, 3d ed., London, 1852).
A popular exposition of the slave-trade hypothesis of Audouard (with additions
by the writer of the present article) will be found in North. Amer. Rev., October
188-L Audouard's three papers were collected under the titie Recueil de
Mémoires sur le Typhus Nautique, ou Fièvre Jaune, Paris, 1825. (C. C.)