Reprinted from MOSQUITO NEWS, Vol. 18, No. 3, September, 1958 THE 1957 STATUS OF YELLOW FEVER IN THE AMERICAS FRED L. SOPER o The professor of infectious diseases in a medical school, located in a city once the scene of a disastrous epidemic of yellow fever, inquired recently if the disease still exists in the Americas. The statistics of the Pan American San- itary Bureau list 77 cases o&ially reported during 1957, surely an insignificant num- ber when related to the hundreds of mil- lions of population of the Western Hemi- sphere. One might, then, be tempted to answer the query with a statement to the effect that yellow fever virus still exists in the Americas but that it is a public health problem of very minor importance. Such a reply would overlook these facts: these 77 cases come from seven countries, (Fig. I), Bolivia, Brazil, Colombia, Guatemala, Panama, Peru and Venezuela; field studies have proven yellow fever virus to be pres- ent in British Honduras, where human cases were not observed during the year; and the range of the virus during 1957 from northwest to southeast has been over 3,500 miles. A look at yellow fever in the Americas through the eyes of foreign health ad- ministrators might alter the indifference of the professor of infectious diseases. The Committee on International Quar- antine of WHO and the World Health Assembly, in meetings devoted to the prep aration, adoption and modification of the International Sanitary Regulations, be- tween rg4g and 1956, encountered greater difficulty in harmonizing the views of dif- ferent countries, and groups of countries, on regulations for yellow fever than was encountered in the solution of all other differences. During early 1956, the WHO sponsored a visit of representatives of Egypt, Philip- pines, Indonesia, British Africa, Belgian *Director, Pan American Sanitary Bureau, Rc- gional O&cc of the World Health Organization. Africa, India, France, and Iraq to several countries in America to get first hand im- pressions of yellow fever here. After one day at the Pan American Sanitary Bureau in Washington the group visited Cuba where there is an active campaign for the eradication of the kdes azgypti mosquito as a part of the continent-wide program to permanently prevent all urban yel- low fever in the Americas. Then on to the then recently reactivated jungle fever zone of Honduras (Fig. 2) where it was learned that after an apparent silence of 15 months, yellow fever virus had not only persisted in Honduras but had moved northward into Guatemala (I). In moving from Honduras to Guate- mala yellow fever virus had left the range of its most widespread vector in the for- ests of South and Central America, Hae- . . . magogus spegazzznrt, and had demon- strated its adaptability to Haemagogus mesodentatus (2) whose range extends well up into Mexico (Fig. 3). In Costa Rica the group visited the San Juan de Dios Hospital where scores of cases of jungle yellow fever were under direct observation in 1951-52, and learned from those who had handled the cases that the clinical picture and high mor- tality of the jungle disease are in all ways similar to those of urban yellow fever. In Panama the group learned the de- tails of the cases of jungle yellow fever infected in 1948 only some ten miles from Panama's International Airport at Tocu- men, and of the 1949 to 1951 march of the epizootic through Western Panama to the frontier with Costa Rica. It was noted that the five hospitalized cases of 1948 were diagnosed post-mortem two months after the first case and two weeks after the last one, and then only because the Santo Tom& Hospital has a full time pathologist. The group could not but wonder how many similar episodes may 1956 L $+ DISCOVERY OF THE SPECIFIC LESIONS OF YELLOW FEVER IN THE LIVER OF VERTEBRATES OTHER T'IFt MAN PASO/WHO 4-58 FIG. I.-Number of cases of yellow fever from countries of the Americas, by political divisions and years, 1954 to 1957. SEPTEMBER, 1958 MOSQUITO NEWS 205 JUNGLE YELLOW FEVER IN CENTRAL AMERICA- 1948-1957 I .SEPTEMBER 1954 "I1r-AUGUST 1954 C,F.R\BBERN `EERUIRY-JULY 1956' P HIcIR*C"I 4c `k AUGL JULY-SEPTEMBER 1952 `C WOVE 1951- SEPTEUBER 1952 FIG. x-Jungle yellow fever in Central America-1948-1957. have passed unnoted during the four dec- ades yellow fever had been absent from the records of Panama and the Canal Zone. That this may have happened is suggested by the appearance in August 1956, of a case of yellow fever in the Santo Tom& Hospital (3), originating in the same jungle area which supplied the cases in 1948. In Bogota, Colombia the visitors saw, at the Carlos Finlay Institute, the record of repeated and continuing incidence of yel- low fever, year after year, and visited the yellow fever study area at San Vicente de Chucuri, Santander (Fig. 4), where in spite of repeated intensive vaccination campaigns, yellow fever cases have been confirmed in twelve of the last twenty-two years. San Vicente de Chucuri is appar- ently a permanent enzootic focus, in which, interestingly enough, monkeys are not present in numbers sufficient to main- tain the virus unless there be some as yet unidentified reservoir or long-lived insect vector. Marsupials are suspected. At Trinidad, B.W.I., the group learned of the early serendipitous discovery of yel- low fever virus in jungle areas in April 1954, four decades after the last report of yellow fever from the Island, and of the urbanization of the jungle infection at Port-of-Spain some months later. Port- of-Spain was the first city in twelve years to report aegypti-transmitted yellow fever and the first maritime port in America to be infected in 25 years. Here, also, it was possible to see the intimate contact, through well paved roads, which exists between jungle and urban areas. The AZdes aegypti mosquito has been widespread in human habitations along the rural high- ways, near the infected forests. In Trini- 206 MOSQUITO NEWS VOL. 18, No. 3 FIG. 3.-Northern limits of the range of monkeys in Central America. dad, reports were also heard of positive neutralization tests carried out in 1953 of young teen-age Trinidadians born long after the last reported yellow fever, indi- cating the possibility of previous unrecog- nized outbreaks on the Island. The visiting group could not fail to note that in spite of evidence indicating the presence of yellow fever virus in Trini- dad during a twelve-month period and its spread throughout the Island, less than a score of cases were reported internation- ally. Obviously many more must have occurred. At BelCm, the gateway to the Amazon Valley, the group from overseas learned of the isolation of yellow fever virus, also serendipitous, from six febrile persons in 1954 not far from the city, when yellow fever was not known to be active in the area. The group also learned of repeated isolations of virus from naturally infected Haemagogus mosquitoes captured in 1955 in the Utinga forest at the edge of the city. At Rio de Janeiro, the terminal point of its American tour, the group visited the FIG. A.-Intervals between the appearance of yellow fever in specific areas. (Courtesy American Journal of Tropical Medicine and Hygiene.) National Yellow Fever Service and heard the story of the rga8-to-1931 struggle to free South Brazil of endemic yellow fever, (Fig. 5), which followed the reinfection of Brazil's beautiful capital, 20 years after Oswald0 Cruz' first victory over the dis- ease in rgo8 (Fig. 4). As stated, the objective of the trip was to give the group a first hand opportunity to see the conditions under which yellow fever occurs in the Americas, in order to judge the threat which yellow fever here may be to other regions. The hope that the trip might result in an immediate les- sening of the fear in the Orient of infec- tion from America was not fulfilled. On the eve of his departure one member of the group declared that his anxiety re- garding the possibility of the infection of Asia with yellow fever had doubled dur- ing the trip. This may well have been the reaction of the entire group, visiting SEPTEMBER, 1958 MOSQUITO NEWS 207 LOCALITIES KNOWN TO HAVE HAD CASES OF YELLOW FEVER FOLLOWING I928 OUTBREAK IN RIO DE JANEIRO FIG. 5.-Localities known to have had cases of yellow fever following the rg28-rgzg outbreak in Rio de Janeiro. the Americas in a year during which only 28 cases of yellow fever have been reported. The indifference of the American pro- fessor of infectious diseases contrasted with the great concern of the health authorities of other regions emphasizes the need of an objective statement of the status of yellow fever in the Americas at the end of 1957. With yellow fever, as with many other infectious diseases, long-term observations are needed for any objective appraisal of the situation, care being taken to make due allowance for any changes which may occur in basic epidemiological conditions. During the century and a half previous to 1900 yellow fever occurred on both the Atlantic and Pacific coasts of North, Cen- tral and South America, and was very ac- tive in the Caribbean and Gulf areas. All countries of the Americas, not excepting even Canada, suffered incursions of yellow fever. Following the confirmation in Igoo by the Reed Commission of Carlos Finlay's theory of the transmission of yellow fever by the A.?des aegypti mosquito, dramatic results were obtained by the reduction of the breeding of this mosquito in endemic centers such as Havana, Panama, and Rio de Janeiro. There was a striking disap- pearance of the disease, not only from the cities where anti-mosquito measures were applied, but also from surrounding and tributary areas. And in 1915, on the basis of this experience, the International Health Board of the Rockefeller Foundation, un- der the leadership of Wickliffe Rose and General Gorgas, sponsored a program for the eradication of yellow fever from the Americas, (Fig. 6), based on the reduction of the A?des aegypti breeding in the endemic centers until the disease should spontaneously disappear. As a result of this program, the last focus of self-sustain- FIG. 6.-Areas reported with yellow fever Igoo to 1931. (Courtesy The Jefferson Medical Col- lege of Philadelphia.) 208 MOSQUITO NEWS VOL. 18, No. 3 ing man-aegypti-man yellow fever infec- tion disappeared from the rural endemic area of northeast Brazil in 1934 (Fig. 7). FIG. T.-Areas reported with yellow fever 1932 to 1957. (Courtesy The Jefferson Medical Col- lege of Philadelphia.) As the man-uegypti-man yellow fever was being eliminated, observation led to the discovery (4) in 1932 and succeeding years, of enzootic and epizootic yellow fever of the tropical forests of America. This was jungle yellow fever, the dis- covery of which gave a ready explanation of the source of virus for some previously unexplained aegypti-transmitted outbreaks in cities and towns isolated from any known source of infection: Rio de Janeiro, Brazil, in 1928; Socorro, Colombia 1929; Guasapati, Venezuela 1929; and Santa Cruz de la Sierra, Bolivia 1932 (5). This discovery showed that the dream of eradicating yellow fever VIRUS was chimerical. The almost simultaneous per- fection of methods for the eradication of the highly domesticated A?des aegypti led inevitably to a program for the eradication of this African invader from the Americas. Even though conditions in the period between rgoo, when the aegypti-transmis- sion of yellow fever was confirmed, and 1931, when the last series of urban out- breaks ended, were quite different from those of the period following 1932, the year in which jungle yellow fever was confirmed and aegypti-eradication begun, it is instructive to compare the distribution of yellow fever in these two periods. The yellow fever reported between 1900 and rgSr (Fig. 6), was distributed around the periphery of South America, around the Caribbean Sea and the Gulf of Mexico, and along the Pacific Coast of Mexico, and Central America. It was almost en- tirely urban yellow fever although the con- temporaneous description of the Trinidad outbreak of 1914 clearly identifies that episode as jungle yellow fever. The re- ports for this early period are almost en- tirely of outbreaks diagnosed clinically and epidemiologically, whereas the reports for the later period 1932 to 1955 (Fig. 7), have come in large part as the result of routine viscerotomy and the histopatho- logical confirmation of unsuspected cases. This is true even of the few cases of AZdes aegypti transmitted yellow fever which have been reported. Yellow fever has been found widely distributed in the in- terior of the continent and even when re- ported close to the coast has only in one instance (Port-of-Spain 1954) infected any international port. The aegypti-trans- mitted yellow fever reported during this period was of two types: endemic rural yellow fever; and isolated urban outbreaks occurring very close, and secondary, to known infected jungle districts. The rural endemic yellow fever of northeast Brazil was terminated in 1934 by extend- ing anti-aegypti measures to large rural areas and has not recurred. In the period from 1932 to 1955 a huge amount of epidemiological information about both urban and jungle yellow fever was collected and studied (6). This period includes the last three vears SEPTEMBER, 1958 MOSQUITO NEWS 209 (1932-1934) of endemic aegypti-trans- mitted yellow fever in northeast Brazil, and the period from 1935 to 1942 when urbanization of jungle virus occurred in 13 towns of Brazil, Paraguay, Bolivia and Colombia, in areas from which the aegypti mosquito has since been eradicated. In order to bring the yellow fever situa- tion of recent years into clearer focus, the distribution of the 1606 cases of yellow fever reported during the decade 1948- 1957 have been brought together in Table I (Fig. 8). During this ten-year period, yellow fever occurred from Guatemala on the north to Argentina on the south and filled in many previous blank spots in the map of jungle yellow fever. The human cases were confirmed in 14 countries- Guatemala, Honduras, Nicaragua, Costa Rica, Panama, Colombia, Venezuela, British Guiana, Trinidad, Ecuador, Peru, Bolivia, Brazil and Argentina-without the occurrence of any aegypti-transmitted outbreaks! Brazil, Colombia and Bolivia reported cases in each of the ten years. In addition yellow fever in monkeys was con- firmed in British Honduras, Venezuela in nine years and Peru in seven. Ecuador reported cases in the Amazon Valley in rg4g and on the Pacific slope in 1951. This is the first report of jungle yellow fever west of the Andes in Ecuador and the first yellow fever on the Pacific slope of South America to be reported since 1921. In rg5o yellow fever extended much farther south in Bolivia than it had been found during 18 years of observation. In Brazil, the Southern States of Mato Grosso, Goias, Minas Gerais, SZo Paulo and Par- ana were invaded from the Amazon Basin, 1950 to 1953, for the third time since 1934. In late 1957 deaths in Mato Gross0 and Goias indicated that a fourth epizo- otic wave was beginning. In 1954, northeastern Venezuela, after apparent freedom from yellow fever for twenty years, was shown to be infected. This area was probably the source of virus for the outbreak of the same year in Trin- idad, already referred to, and is also not- able as originating the first infectious case of yellow fever known to travel by air from the jungle to a distant aegypti-in- fested urban center-Sucre State to Ca- racas. In 1955 and again in 1956, jungle yellow fever was reported in the State of Aragua in north central Venezuela, far TABLE I.-Reported Cases of Yellow Fever in the Americas, x948-1957 Area 1948 1949 1950 1951 1952 1953 `954 1955 1956 1957 TOLJ Total 54 I74 391 312 341 89 97* 42 28 78 1606f Argentina +* 1 - - - - - - - Bolivia 30 156 354 3 1 I8 2 59: Brazil ** 3 6 4 50 221 39 9 ;: 6 1; 2 IO 352 British Guiana ** 1 - - - - - - --- I British Honduras - - - - - _ - - -a** - Colombia ** 12 3 12 26 16 II I2 22 16 35 165 Costa Rica - - - 180 93 5 - - - - 278 Ecuador I - 42 - - - - - - 43 Guatemala - - - - - - - - *** 3 3 Honduras *+ - - - - - I+* _ Nicaragua ** - - - - 7 s : 1 - - 1; Panama 5 4 2 3 I - - - I 2 18 PelU I 4 16 4 I - 26 - - 3 55 Trinidad and Tobago ** - - - - - Venezuela ** I - 3 4 1 s :;* ; 3 6 2:" *Jungle yellow fever, with the exception of 3 cases in Trinidad in 1954. ** All cases with laboratory confirmation. *** Evidence of activity of the virus of yellow fever in howler monkeys (Alouafra zp.) 1948 -- FIG. 8.-Number of cases of jungle yellow fever from countries of the Americas, by political divisions (Courtesy American Journal of Tropical Medicine and Hygiene.) 212 MOSQUITO NEWS VOL. 18, No. 3 from any previous reported focus of infec- tion and only some 50 miles from the Capital. In Panama, as already noted, yellow fever appeared in 1948 as a jungle infec- tion east of the Canal, spread during the next five years across the Canal and up the Isthmus to Costa Rica and Nicaragua (7). The events of the next three years, 1954, 1955, 1956, (Fig. I), were to show that jungle vellow fever had not vet exhausted . Its ability to surprise the epidemiologists. in Central America, in 1954, (Fig. 2), the enzootic which had previously been traced easily in Costa Rica and Nicaragua by the finding of sick and dead monkeys, was followed with difficulty across Hon- duras to the Ulua Valley near the frontier with Guatemala. During 1955, no yellow fever activity, either in man or in monkeys, was reported in Central America. Surprisingly, early in 1956, activity among monkeys was re- ported in Honduras, in the same area where the activity had ceased 15 months before ( I). Simultaneously, yellow fever among monkeys was observed across the border in Guatemala indicating progres- sion of the epizootic wave. The year 1956 was one of considerable yellow fever activity in monkeys in Guatemala, without the occurrence of reported human cases. The activity in monkeys continued in 1957 in Guatemala and British Honduras; though human cases were confirmed in Guatemala. The recurrence in Panama of jungle yellow fever in 1956 (3) and 1957 in the same districts where cases occurred in 1948, and the present epizootic wave, which has now reached Guatemala, when taken together raise the question of whether a second wave may follow the preceding one so soon in Central America where the susceptible monkey population was greatly reduced by mortality from yellow fever just a few years ago. In Brazil, the 1g50~3 outbreak in the Southern States stopped unexpectedly. Apparently drought conditions curtailed this epizootic before it completed its sweep through the forests of southern Brazil, practically all of which were invaded dur- ing the 1934 to rg4o epizootic. The only cases reported in Brazil during 1954 were found through routine virus isolations in an otherwise silent area near BeKm at the mouth of the Amazon. In 1955 likewise yellow fever reported from Brazil was limited to this same area. In 1956 and 1957 there were a few scattered cases in the Amazon Valley. The cumulative reports of yellow fever since 1932 and the unfolding picture of yellow fever since 1946, reveal clearly the absolute necessity of continuous observa- tion and study if any appreciation, even approximate, of the sweep of epizootic cycles is to be obtained, for some of these cycles require a decade or longer for com- pletion. Even the 25.year period has been too short (Fig. 7), to give the whole picture of jungle fever in the Americas. This is due to the relatively long intervals which have occurred in certain areas between epizootic waves, as well as to the failure to recognize and report many, if not almost all, of the resultant human cases. The progress of a wave depends upon at least three coincident factors: the introduction of the virus; the existence of an adequate population of susceptible vertebrates; and weather suitable to multiplication and maintenance of adequate numbers of mos- quito vectors. The study of the intervals between the appearance of yellow fever in specific areas indicates that yellow fever persists almost constantly in certain small areas, returns repeatedly after short periods of freedom in other areas, and recurs only after long and irregular absences in yet others. Rio de Janeiro, already referred to as having been reinfected by jungle yellow fever virus in 1928, twenty years after the city had been freed of endemic yellow fever by Oswaldo Cruz, was again bom- barded by jungle virus in a number of known infectious cases coming into the city from nearby infected areas in 1938. SEPTEMBER, 1958 MOSQUITO NEWS 213 During the past rg years jungle yellow fever has not been observed in areas close to Rio nor have recognized cases appeared from further afield. Other areas have re- ported the recurrence of yellow fever after intervals of two or three years up to ten, twenty and even forty years. This discussion of the status of yellow fever in 1957 has been largely limited to the official reports of the distribution of jungle yellow fever. Since endemic aegypri-transmitted yel- low fever no longer exists in the Americas, the problem of yellow fever during the past 20 years has been related to enzootic and epizootic yellow fever as a source of virus for jungle yellow fever cases, and to jungle yellow fever cases as a source of infection for AZdes aegypti-infested towns. The questions to be answered in assess- ing the yellow fever situation as a threat to man are: What is the importance of jungle yellow fever to rural populations of tropical America? What is the threat of the urbanization of jungle yellow fever virus in cities and towns in enzootic and epizootic areas? What is the international threat of jungle yellow fever? Jungle yellow fever is clinically and pathologically indistinguishable from ur- ban yellow fever and is just as dangerous to the person infected in or near the forest as to the city victim. The jungle disease is however generally limited to those living or working in or very close to the tropical forest or entering the forest for recreation or travel. Figure g shows the transmis- sion cycle of jungle yellow fever in tropi- cal America. Where the homes are closely surrounded by forest in a permanently enzootic focus (Ilheus, Brazil) or where Indian tribes live in the forest, the people get infected with yellow fever even during the early years of life. Where road or lumber gangs enter the forest and where the forest is being cleared for agriculture the disease becomes almost occupational in its distribu- tion and attacks a high percentage of young adult males at their most productive period (Espirito Santo, 1940; 108 deaths, IOO in males over 16) (San Vicente de Chucuri, Colombia 1936-1955; 55 deaths, 45 farmers, 7 women, 3 children). Where relatively light work, such as cof- fee picking, brings both women as well as men close to the forest, the disease tends to attack both men and women and even a considerable number of the children who accompany their parents to the fields. Thus it is clearly not necessary to chop down a tree to get yellow fever. The development of a satisfactory yel- low fever vaccine in 1936 greatly reduced the threat of jungle yellow fever, and has, in fact, practically eliminated it for those who are vaccinated. The American nations are fortunate in having free access to vaccine, produced in the Oswald0 Cruz Institute, in Brazil, and in the Carlos Finlay Institute, in Colom- bia, in both with the collaboration of the Pan American Sanitary Bureau. Vaccina- tion produces long lasting, probably perm- anent, immunity. What is the threat of urbanization of 2'4 MOSQUITO NEWS VOL. i8, No. 3 4wAs IN V~HICH m AEGYPTI STILL EXISTS 1/ 1 AREA DKLAREO RECEPWC TO YELLOW WER BY ,"I $ u. s. PUBLIC HEALTH SERVlCf ZONES WITH ERlDlClTlON CAMPAIGN ZONES WlTHDUT ERADICATION CAMPAlGN XREAS IN WHICH AEDES AEtypT, IS NO LONGER REPoRTEo STATUS OF AFDES AEGYPT/ ERADICATION CAMPAIGN IN THE WESTERN HEMISPHERE-31 DECE,&,GcR 195.7 Pro. IO.-Status of the AEdes aegypti eradication campaign in the Western Hemisphere on December 31, 1957. (From the Annual Report for 1957 of the Director, Pan American Sanitary Bureau.) SEPTEMBER, 1958 MOSQUITO NEWS 2'5 jungle yellow fever virus near infected forests? All observed urbanization of jungle yel- low fever virus has occurred in towns rela- tively close to infected forests. The possi- bility of the introduction of yellow fever virus from forest to urban areas has been greatly reduced by the vaccination of large blocks of the populations living in jungle yellow fever areas: in Brazil, Colombia, Venezuela, Trinidad, Panama, Costa Rica, Nicaragua, Honduras, Guatemala and Mexico. However, vaccination is never complete, and absolute protection of towns can come only from the eradication of the aegypti mosquito. The program for the eradication of the Azdes aegypti mosquito from the Amer- icas has progressed to the point (Fig. IO), where there is very little opportunity for cases from infected jungle areas to infect cities without undertaking an international trip. From Argentina to Guatemala, the aegypti mosquito has either been eradi- cated or is under heavy attack in all of the countries where jungle yellow fever has been reported in the past 25 years. To prevent reinfestation of those areas which have been, or are being, cleared of kdes uegypti it is essential that aegypti be eradi- cated also from the United States, Cuba, the Dominican Republic, Haiti, Puerto Rico, Jamaica, and the other Caribbean is- lands-where conditions for jungle yellow fever do not exist-as well as from Mexico where jungle yellow fever could occur, and which also has Aifdes aegypti. What is the international threat of jun- gle yellow fever? In its extra-human res- ervoir the virus of yellow fever apparently moves through contiguous or nearly con- tiguous forest areas quite independently of man. The forest areas may all be in one large country like Brazil, or in half a dozen small ones like the Central Ameri- can countries. The virus takes cognizance only of ecological boundaries, not of na- tional ones (8). It so happens that jungle yellow fever has never been observed to move inter- But in Venezuela in 1954 a man in the early-i.e. infectious-stage of jungle yel- low fever traveled by plane from Sucre State to Caracas, a distance of several hun- dred miles. Facilities for both highway and air travel are constantly improving in the outlying areas of jungle yellow fever countries. This places those areas in closer contact, through man, with heavily used national and international routes of travel. Aegypti-infested countries, that could formerly rely on relative isolation from virus-infested jungles to protect them from yellow fever, may soon find that they are no longer effectively isolated. SUMMARY. Yellow fever virus is always present, with variable year-to-year distribu- tion, throughout the tropical and subtropi- cal forests of America from Mexico to Argentina. In the decade 1948-1957 there was labo- ratory evidence of virus activity in 15 coun- tries and territories. From four to eight countries were known to be involved each year. In three instances the presence of the virus was observed only in howler mon- keys (Ahatta sp.). The countries in- volved were British Honduras, Guatemala and Honduras, in the years 1956 and 1957. Jungle yellow fever is a serious threat to rural populations and is a permanent source of virus for the reinfection of such cities and towns, as may be infested with Azdes mgypti, in the same country with infected forests and even of such cities and towns in other countries. Maximum guarantees against yellow fever depend on the widespread vaccina- tion of rural populations and on the eradi- cation of the At;des uegypti mosquito from all of the Americas. I. JOHNSON, C. M. and FARNSWORTH, S. F. Results of recent studies of vellow fever in Middle America. Preliminary Not;. Bol. Of. San. Pan. 1956, vol. 41, pp. 182-183. 2. GALINDO, P., RODANICHE, E., and TRAPIDO, H. Experimental transmission of yellow fever by Central American species of Haemagogus and Sabethes chlwopterus. Amer. Jour. Trop. Med. _ . nationally along human routes of travel. and Hyg., 1956, vol. 5, pp. 1022-1031. 216 MOSQUITO NEWS VOL. 18, No. 3 3. Weekly Epidemiological Report, PASB/ WHO, No. 35, August 28, 1956. 4. SOPER, F. L., PENNA, H. A., et al. Yellow fever without A&s aegypti. Study of a rural epidemic in the Valle do Chanaan, Espirito Santo, Brazil, rg32. Amer. Jour. Hyg. 1933, vol. 18, PP. 555587. 5. STRODE, G. K., Ed. Yellow Fever. New York. McGraw-Hill, 1951. 6. YELLOW FEVER CONFERENCE, 21-22 DE- CEMBER 1954. Amer. Jour. Trop. Med. and Hyg., 1955, vol. 4, PP. 571-661. 7. TRAPIDO, H. and GALINDO, P. The epidemi- ology of yellow fever in Middle America. Exper. Parasit., 1956, vol. 5, pp. 285-323. 8. BOSHELL-M~NRIQUE, J. Yellow fever in Cen- tral America-The post-war spread as a threat. Yellow fevera symposium in commemoration of Carlos J. Finlay. The Jefferson Medical College of Philadelphia, 22-23 September 1955, pp. 61-69. April 1, 1968 lLf- 9e ___, NOTES ON NO. l6.& of FL5 BIBLIOGRAPHY 1958 (Sept.). The 194'7 status of yellow fever in the Americas. Mosquito News 18 (3): 203-216. Page 210 The map for 1946 shows no yellow fever for south Brazil. As a matter of fact, no cases were reported there for the year. However, jungle yellow fever had moved from the Amazon Valley into the valley of the River Plate on the divide in Mato Gross0 in IS&./J. This had spread into Goias and Ninas Gerais, reaching to the Rio Grande on the frontier "i,th Sio Paulo. The infection apparently died out during the year 1945, Sao Paul0 being spared the next year. However, viscerotomy revealed a very probable case of yellow fever at Dourados in southern Mato Gross0 in 1946. This was given a diagnosis of leptospirosis --not yeUww fever--at the time. Reexamination in 1947 by FIS led to the belief that this had been a case of yellow fever ard that there was a possibility that yellow fever virus had moved through southern Mato Gross0 into Paraguay and would eventually be manifested further south. As a matter of fact, single cases were proven by viscerotomy for the province of Misiones in Argentina ard the state of Rio Grande do Sul in Drazil in 1948.