A Possible Connection between the 1878 Yellow Fever Epidemic in the Southern United States and the 1877–78 El Niño Episode Henry F. Diaz* and Gregory J. McCabe+
ABSTRACT One of the most severe outbreaks of yellow fever, a viral disease transmitted by the Aedes aegypti mosquito, affected the southern United States in the summer of 1878. The economic and human toll was enormous, and the city of Memphis, Tennessee, was one of the most affected. The authors suggest that as a consequence of one of the strongest El Niño episodes on record—that which occurred in 1877–78—exceptional climate anomalies occurred in the United States (as well as in many other parts of the world), which may have been partly responsible for the widespread nature and severity of the 1878 yellow fever outbreak. This study documents some of the extreme climate anomalies that were recorded in 1877 and 1878 in parts of the eastern United States, with particular emphasis on highlighting the evolution of these anomalies, as they might have contributed to the epidemic. Other years with major outbreaks of yellow fever in the eighteenth and nineteenth centuries also occurred during the course of El Niño episodes, a fact that appears not to have been noted before in the literature.
1. Introduction Yellow fever was first recorded in British North America, in what is today the United States, in 1693 (Reed and Carroll 1911; Patterson 1992). However, its first recorded appearance within the present boundaries of the United States was in Spanish Florida around 1649–50 (Patterson 1992). Yellow fever is an acute viral disease transmitted to humans by the bite of the female Aedes aegypti mosquito. A 1911 U.S. Senate Report on the disease highlights the fundamental work that Major Walter Reed and his colleagues performed around the turn of the twentieth century to identify the means of infection and develop procedures to prevent its spread. Reed and his team of U.S. Army doctors showed that yellow fever is transmitted when an infected individual is bitten by a single species of mosquito, and after an incubation period, *NOAA/ERL/CDC, Boulder, Colorado. + U.S. Geological Survey, Denver Federal Center, Denver, Colorado. Corresponding author address: Henry F. Diaz, OAR, NOAA/ERL, 325 Broadway, Boulder, CO 80303. E-mail:
[email protected] In final form 30 September 1998.
Bulletin of the American Meteorological Society
which varies from 4 days to 2 weeks (depending on the temperature), the mosquito bites another individual, thereby passing the pathogen from one person to another. The vector carrier, the female Aedes aegypti mosquito, is an urban insect that breeds in small bodies of water, typically near houses, where one often finds water receptacles, such as gutters, fountains, pots, etc. For A. aegypti the temperature limits for functional activity, breeding, and feeding are from approximately 20° to 39°C. The optimum temperature is from 27° to 31°C (Carter 1931; Smith and Gibson 1986). Temperatures below 0°C are fatal to the adult. At a temperature of 24°C the mosquito feeds on an average of every four days. As temperatures decrease, the period between feedings increases (Smith and Gibson 1986). At temperatures above 39°C, A. aegypti become motionless, and die when temperatures exceed 41°C (Christophers 1960). High humidity, in concert with moderately high temperature, favors not only the duration of life of A. aegypti, but also affects the general activity of the mosquito (Smith and Gibson 1986). Research has shown that there is a steady increase in biting activity of mosquitoes when relative humidities increase from 60% to 96% (Christophers 1986). 21
The human toll that this disease exacted in many parts of the world can best be gauged by the following quote from Reed and Carroll (1911): “The prevention of yellow fever [in the United States], especially in the 19th century, has commanded the attention of public health officials, [due to] . . . the alarmingly rapid spread and course of this disease when once it had obtained a foothold, and the high mortality with which its epidemics have generally been attended. During its brief reign—July to October—its ravages were such as to completely paralyze both the social and commercial interests of a given city, and even an entire section of our country.” One of the more severe epidemics to have affected the southern United States in the nineteenth century was that of 1878: “the great epidemic of 1878 resulted in the loss of 16,000 lives, and it has been estimated that the total loss to the country resulting from this epidemic was not less than $100,000,000” (Reed and Carroll 1911). Other estimates placed the death toll as high as 20 000 people, out of about 100 000 cases of the disease, with attendant economic losses of as much as $200 million (Bloom 1993). Memphis, Tennessee, was one of the most affected areas, with about 17 600 cases recorded resulting in a death toll of 5150—more than 1 out of 4 cases (Carroll 1911). As a result of the studies that Reed and others carried out to identify the source and means of transmission of yellow fever (hereafter, YF), the last epidemic of the disease in the United States occurred on the Gulf Coast in 1905—during an extended El Niño episode that peaked in 1905 (see Quinn 1992). The present study considers the effect that the exceptional warm El Niño episode of 1877–78 had on the climate of the central and southern United States (see Kiladis and Diaz 1986), which produced unprecedented temperature and precipitation anomalies from mid-1877 to late 1878 (see also Bloom 1993, 26–27) and may have contributed toward enhancing the mosquito population during the 1878 summer season, and to extending the active mosquito season into late spring and early autumn of that year. Carroll (1911) underscored the frequently made observations by several medical chroniclers of the time, that mosquitoes were uncommonly numerous during these epidemic years. It was not until the end of the nineteenth century, however, that the apparently high number of mosquitoes noted during many YF outbreaks was connected to the disease. In temperate climates, which encompass most of the contiguous United States, the mosquito does not survive the win22
ter, so that unless the virus is introduced again the following warm season, the cycle is broken. This may explain the episodic nature of the yellow fever outbreaks in the United States (the disease confers immunity to the survivors). We surmise that much above-normal precipitation in the several months immediately preceding major YF outbreaks, together with abnormally warm conditions from late spring through the summer, were in part responsible for the epidemics by greatly increasing the mosquito population during those years. 2. The yellow fever epidemic of 1878 During the summer of 1878, Memphis, a city of some 50 000 people, “found itself literally decimated, after passing through an ordeal much worse than decimation if we consider the city’s mostly deserted condition at the time.” The Memphis epidemic “stands out as one of the very worst catastrophes in American urban history, its toll surpassing that of the Chicago fire, San Francisco earthquake, and Johnstown flood combined” (Bloom 1993, 1). a. Climatic conditions around Memphis A likely time for Aedes aegypti to hatch in the warmer climates of the South would be in April or May when temperatures during daylight hours can be rather warm—precipitation in this region tends to be plentiful throughout the year and the mosquito generally had available to it outdoor containers of water (empty barrels, cisterns, discarded tin cans, etc.) in which eggs could be laid. The spring of 1878 was warm, and weather diaries kept by observers contain remarks referring to the early blossoming of trees in the spring. In April 1878, the mean temperature was 16.9°C (compared to the modern normal of about 16.8°C) and precipitation was 303 mm (normal is around 130 mm). In May the mean temperature was 21.9°C and precipitation totaled 93 mm (compared to normals of 21.4°C and 112 mm, respectively). During the period of hatching of eggs and maturing of the individual insect, the months of April–June, precipitation was about 150% of normal, and temperatures averaged about 1.5°C above the mean. These conditions were favorable for the hatching and maturing of A. aegypti. The months of June and July were also warm with a mean monthly temperature in June of 24.6°C and a mean temperature of 28.6°C in July (modern averages of 25.7° and 27.4°C, respectively). Precipitation toVol. 80, No. 1, January 1999
taled 139 mm in June (normal is 93 mm), with 13 rainy days in the month, assuring adequate water supplies for breeding. In July and August rainfall was somewhat below normal (about 90% of the mean), but temperatures remained in the optimum range, averaging about 0.5°C above average in Memphis and throughout much of the South. As the Aedes aegypti breeds in water, the availability of water in breeding areas is critical. Figure 1a illustrates the high precipitation experienced in Memphis in 1877, which extended, with the exception of the winter months, into the spring of 1878. While the total amount of rainfall is important, the number of rainy days is also of great importance. A season may have a high rainfall total, but all of the precipitation may have fallen in a few intense storms. Storms separated by long dry periods may not provide the constant water supply needed for proper breeding areas for the mosquito. Thus, the number of rainy days during a breeding season is of importance in that this variable indicates the degree to which a constant supply of moisture is available to provide proper breeding grounds. From the fall of 1877 to the summer of 1878, conditions were similar to those in Memphis at other points in the lower Mississippi River basin that year, as evidenced in the precipitation record for Vicksburg, Mississippi, (Fig. 1b) and New Orleans, Louisiana (Fig. 1c). Figure 2 (top) illustrates the number of rainy days during March–August in Memphis, for the years 1871–80 (the climate record for Memphis begins in 1871). It is clear from Fig. 2 (top) that 1878 was a period of above-normal raininess. Although other years exhibit an equivalent number of wet days, 1878 clearly exhibits a relatively high value for the period. The previous year, 1877, was also associated with a high number of rainy days (and, as we have seen, high precipitation totals); this is important because wetterthan-average climate conditions during 1877 would have contributed to a greater than normal number of mosquito eggs, which would lead to the development of a strong population base during 1878. Temperature is an extremely important weather factor that contributes to the development and activity of A. aegypti populations. As temperatures below 0°C are fatal to this species, thereby preventing the development of larvae, the number of days during the winter months when temperatures below 0°C are experienced may serve to indicate the degree to which a base population could be killed and would then have to rebuild during the subsequent warm season. Bulletin of the American Meteorological Society
FIG. 1. Profile of precipitation anomalies at (a) Memphis, TN, (b) Vicksburg, MS, and (c) New Orleans, LA, for 1877–78. Departures are with respect to the period of record mean and are plotted as 3-month running seasons.
Figure 2 (middle) shows the number of days in Memphis with a minimum temperature below 0°C, during November–February. Data for the years 1871– 73 were unavailable. Note how the number of days with a minimum temperature below 0°C is well below average for the winter of 1877–78 (labeled as 1878). The winter mean temperature (December–February) from about Vicksburg northward along the Mississippi was about 1°–2°C above the long-term average, and March 1878 was exceptionally warm across much of this region (see Fig. 4 in Kiladis and Diaz 1986, and further discussion below). The relatively mild winter and early spring temperatures likely contributed to the survival of many of the mosquito eggs through the winter months. A prime temperature threshold that limits the movement of A. aegypti is 10°C. When temperatures fall below this value the insect is incapable of moving. Figure 2 (bottom) gives the number of days with a mean temperature below 10°C during the months of March–August. The year 1878 stands out as one with very few days with a mean temperature below 10°C 23
during the spring and summer. Thus, during that year, temperature conditions in Memphis were highly favorable for the movement of the mosquito. In general, the climate of Memphis and much of the southeast United States is suitable for the development and activity of A. aegypti. The temperatures are warm during the summer, winters are relatively mild, and humidity levels are high. During the 1870s there were several years with warm summers, relatively mild winters, and high rain day totals. However, the fall of 1877 through the summer of 1878 appears to have been particularly favorable for the presence of high numbers of A. aegypti, with the occurrence of a mild winter and spring, followed by a warm summer, and most months experiencing abundant rainfall. b. Climatic conditions in other parts of the southeast United States, 1877–78 Kiladis and Diaz (1986) presented a comprehensive survey of the global climatic signals associated with the 1877–78 major El Niño episode. That study was an attempt to place the major El Niño event of 1982/83 in some historical perspective. The authors showed that record or near-record temperature and precipitation anomalies were recorded in many parts of the world. In particular, the extended winter season (November–April) of 1877–78 in the United States was exceptionally warm in the interior states and wet along the west and southeast coasts. In the middle and upper Mississippi Valley temperatures were unusually warm in the spring of 1878. This is illustrated in Fig. 3, which shows a map of temperature departures from the long-term mean for the late-winter–early-spring months of February–April (the map for the nominal spring months of March– May is nearly identical). In the southeast United States, mean temperatures for these months exceeded 1°C in most areas, and 2°C throughout the stem of the Mississippi River. Summer temperatures were nearnormal or slightly above the mean, and the relative warmth extended into September. The summer of 1877 was very wet in the Memphis area, which recorded nearly 300% of average summer (June–Au-
FIG. 2. Climate statistics for Memphis, TN, in the years spanning the 1878 outbreak of yellow fever. (a) Total number of rain days from March through August for the years 1871–80; (b) total number of days with minimum temperatures below 0°C for the months November–February for the years 1871–80; and (c) total number of days with a mean temperature below 10°C for the months March–August for the years 1871–80. 24
Vol. 80, No. 1, January 1999
gust) rainfall that year (see also Figs. 1 and 2a). It was wet throughout the southeast during the 1877 fall season. Spring and summer 1878 precipitation along the Mississippi from Cairo, Illinois, to New Orleans was near to above normal. One of the wetter 3-month periods along the lower stem of the Mississippi River occurred in April –June (maps not shown). Hence, climatic factors associated with the major El Niño episode of 1877–78 may have contributed to the severe YF outbreak in the southeast United States by promoting the reproduction, survival, and propagation of the A. aegypti mosquito. 3. Other U.S. yellow fever outbreaks and El Niño
FIG. 3. Map showing temperature departures (°C) from record mean for stations in the southeast United States for the months of February–April of 1878. Magnitude of anomalies is proportional to the size of the circles. Solid dots identify the locations of Cairo, IL, Memphis, TN, and Vicksburg, MS.
It is of interest here to note that YF outbreaks were documented in Philadelphia in 1793 following a very strong El Niño, in 1797 following a moderate-to-strong El Niño, and in 1802–03 during a strong El Niño; outbreaks were also documented in St. Augustine, Florida, the major outbreaks of yellow fever in the United in 1839, also following a strong El Niño, and along States since the late eighteenth century have been asthe Gulf Coast in 1853 (see Duffy 1966), following a sociated with El Niño episodes. After the great YF moderate El Niño episode (see Quinn 1992). Typical epidemic of 1878, only a handful of relatively small of the impact of El Niño in the United States during outbreaks of the disease were reported in the United the cold season, the winter of 1853 had a marked absence of cold air outbreaks. The spring was characterized as having TABLE 1. Years with major (> 1000 deaths) yellow fever epidemics, 1793–1905, arrived early and the summer to have in the United States. Data taken from Patterson (1993). El Niño years taken from been rather warm and humid. This is Quinn (1992) and Quinn and Neal (1992). likely to have led to a longer than normal active period for A. aegypti and a larger Year Deaths Main location(s) El Niño event than normal mosquito population that year. Indeed, mosquitoes were reported 1793 ca. 5000 Philadelphia Yes to have been remarkably numerous along the Gulf Coast in 1853 (Bloom 1993, 1797 > 1300 Philadelphia Yes 43). Patterson (1992) also lists the years 1802–03 > 1000 Charleston to New York Yes 1867, 1873, 1879, and 1897 in the latter half of the nineteenth century as experi1817 > 1000 Charleston, New Orleans Yes encing major outbreaks of YF in the South, particularly from Memphis to 1837–39 > 1500 Galveston to Charleston Yes New Orleans, Louisiana. Of these other 1847–49 > 4000 mostly in New Orleans No outbreak years, 1873 and 1897 are listed by Quinn (1992) as moderate El Niño 1852–55 > 15 000 Galveston to Charleston* Yes events, while 1867 was the start year of an extended strong event. 1876 1200 Savannah No Table 1 lists the years with major YF outbreaks in the United States and 1878 ca. 20 000 Memphis, New Orleans Yes whether these years were associated with the occurrence of El Niño. Nearly all of *Greatest death toll occurred in New Orleans with about 15 000 deaths reported. Bulletin of the American Meteorological Society
25
States, resulting in fewer than 1000 deaths. Of these, the most severe were the 1888 outbreak in Jacksonville, Florida, the 1897 outbreak in Louisiana and other Gulf Coast towns,and the 1905 Gulf Coast outbreak, primarily in New Orleans. The 1905 YF episode was the last United States epidemic of this disease. All of these years were associated with El Niño events. It is beyond the scope of this study to consider the range of epidemiological and social factors that conspired to make the 1878 YF outbreak the national disaster that it was. The reader is referred to the bibliographic references listed, in particular, Bloom (1993), Duffy (1966), and Patterson (1992) for further study. Undoubtedly, the YF epidemic of 1878 in Memphis and elsewhere along the Mississippi River was a result of both social and epidemiological, as well as climatic factors that came together at the same time. Some of the more important of these nonclimatic factors are a supply of infected individuals for the mosquito to feed on and propagate the virus, a relatively large population of nonimmune individuals, and the absence of preventive public health actions, such as the removal of water containers where the mosquito could breed, mosquito eradication programs, or vaccines. Clearly, although El Niño events have continued to occur in this century, after 1905, with the discovery of the source of the infection in 1900 by W. Reed and his colleagues, there have been no YF epidemics recorded in the United States. Nevertheless, the strong coincidence between severe YF outbreaks and the occurrence of El Niño events over the previous century suggests a climatic connection. This is likely to be in the form of mild winters preceding the summer of the outbreak, together with ample precipitation to provide breeding pools for the mosquito vector and a warm summer to promote high mosquito activity.
1960; Bruesch 1978; Smith and Gibson 1986). However, the 1877–78 winter, as well as the spring of 1878, were warmer than normal, which likely aided the early migration of the mosquito into the Memphis area. Much of the unusual weather was likely the result of the strong El Niño episode that was recorded in 1877– 78 (Kiladis and Diaz 1986). The yellow fever outbreak greatly contributed to the financial collapse of Memphis in 1878. The corporate charter of the city was revoked in January of 1879. But a rebuilding process began, and as part of that process a sewer and waterworks system was established in the 1880s. Before the project was started, yellow fever made another appearance in Memphis in 1879 but with a much smaller effect. Much of the remaining population had developed an immunity from surviving yellow fever in 1878 (White 1978). The city instituted an artesian well system that eliminated the cistern and rain barrel system of water storage and removed breeding areas. New Orleans also established an improved sanitation system, piped water system, and a quarantine system that drastically cut both the incidence and mortality rate of yellow fever. The influx of infected individuals into a pool of nonimmune population was undoubtedly the most important epidemiological factor for the outbreak of yellow fever in Memphis and other southern United States cities. However, in many of those years, these outbreaks were likely aided and abetted by a larger than normal population of A. aegypti that may have been the result of significantly wetter and warmer than normal conditions. The anomalous climatic conditions prevalent in the southeast United States, associated with the major El Niño episode of 1877–78, likely contributed to this large outbreak of the disease during 1878. References
4. Conclusions During 1878 one of the most virulent strains of yellow fever had entered the southeast. The prevalence of water-filled rain barrels and cisterns during an abnormally wet period provided ample breeding grounds for the mosquito, and the movement of people, mainly on boats along the Mississippi River, carried the disease to Memphis. The climatic conditions were at an optimum for the A. aegypti to develop and spread the disease. Usually, Memphis lies north of the general poleward limit of A. aegypti distribution (Christophers 26
Bloom, K. J., 1993: The Mississippi Valley’s Great Yellow Fever Epidemic of 1878. Louisiana State University Press, 290 pp. Bruesch, S. R., 1978: Yellow fever in Tennessee. J. Tenn. Med. Assoc., 71, No. 12. Carroll, J., 1911: The transmission of yellow fever. A Compilation of Various Publications, Results of the work of Maj. Walter Reed, Medical Corps, United States Army, and the Yellow Fever Commission, U.S. Government Printing Office, Document 822, 175–215. Carter, H. R., 1931: Yellow Fever: An Epidemiological and Historical Study of Its Place of Origin. The Williams and Wilkins Co., 308 pp.
Vol. 80, No. 1, January 1999
Christophers, S. R., 1960: Aedes Aegypti (L.): The Yellow Fever Mosquito; Its Life History, Bionomics, and Structure. Cambridge University Press, 738 pp. Duffy, J., 1966: Sword of Pestilence. Louisiana State University Press, 191 pp. Kiladis, G. N., and H. F. Diaz, 1986: An analysis of the 1877–78 ENSO episode and comparison with 1982–83. Mon. Wea. Rev., 114, 1035–1047. Patterson, K. D., 1992: Yellow fever epidemics and mortality in the United States, 1693–1905. Soc. Sci. Med., 34, 855–865. Quinn, W. H., 1992: A study of Southern Oscillation-related activity for A.D. 622–1900 incorporating Nile River flood data. El Niño, Historical and Paleoclimatic Aspects of the Southern Oscillation, H. F. Diaz and V. Markgraf, Eds., Cambridge University Press, 119–149.
Bulletin of the American Meteorological Society
——, and V. T. Neal, 1992: The historical record of El Niño events. Climate Since A.D. 1500, R. S. Bradley and P. D. Jones, Eds., Routledge, 623–648. Reed, W., and J. Carroll, 1911: The prevention of yellow fever. A Compilation of Various Publications. Results of the work of Maj. Walter Reed, Medical Corps, United States Army, and the Yellow Fever Commission, U.S. Government Printing Office, Document 822, 131–148. Smith, C. E. G., and M. E. Gibson, 1986: Yellow fever in South Wales, 1865. Med. History, 30, 322–340. White, M., 1978: Yellow fever. Commerc. Appeal, 31 October, 2A–8A.
27
