Great Epidemics in History
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It is widely assumed that infectious diseases have always been linked to life on earth. Actually, primitive bacteria are millions of years older than the human being. However, it seems that generalised cases of infection, i.e. epidemics, did not appear until the advent of the great ancient empires and the progressive growth in population. This has a very simple explanation: an infective agent needs to find a new host once the original is dead. Since people in prehistoric times used to live in small clans, the propagation of disease was basically reduced to the members of that close group. It is supposed that anthrax was a common infection at that time, when the early human hunters would contract the disease from sick animals or by eating tainted meat. The first recorded accounts of epidemics must be traced back to the writings of the Sumerians, Babylonians, Hebrews, Hittites, Egyptians, Greeks, Romans, Indians and Chinese. From these, perhaps the best known in the western world, due to its relevance, is the Biblical ten plagues of Egypt. Only the fifth, the pest that kills the Egyptian cattle (Exodus 9: 1-7) and, especially, the sixth, the ulcers and tumours that afflict every Egyptian and animal (Exodus 9: 8-12) can be considered in the medical epidemic sense. However, the renowned erudite Isaac Asimov does not give much validity to this reference. In his view, outside the Bible itself there seems to be no other quotations to support such important pestilences, which should have caused many casualties (1997: 124).

An initial epidemic to consider is the Great Plague of Athens, which started in 430 BC and lasted five years. There is a well-known report in Thucydides’ History of the Peloponnesian War, which describes in full detail how the plague came by ship from Egypt (1972: 151-6). It spread swiftly through the city, causing thousands of casualties that piled up in the streets. It is difficult to determine from the related characteristics whether it was smallpox, measles or any such contagious disease, but people developed fever, bouts of coughing, diarrhoea and sores that became ulcers. Either the agent is unknown today or perhaps the symptoms were exaggerated, but the epidemic contributed substantially to the Athenian defeat in the war against Sparta and the polis never fully regained its past splendour. Beyond its dramatic human and cultural effects, the social cohesion was greatly affected. There was widespread crime which went unpunished and basic human rights vanished. This is a scenario that is clearly mimicked in Ouellette’s The Third Pandemic twenty-four centuries later, showing a manifest projection of what we could face in the eventuality of a devastating pandemic.
Later on, the Roman Empire suffered a similar epidemic. It is only known that the disease also came from northern Africa by ship during the war against Carthage and that it took as many lives as the earlier Greek one. In AD 79, another plague, either anthrax or malaria, travelled down the Nile into the Mediterranean, where it spread through Mesopotamia, northern Greece and eventually Rome. Once in the heart of the Empire, soldiers and merchants would help it reach the most distant confines. In AD 166, Roman troops that who been sent two years earlier to Syria to subdue a revolt, brought back a previously unknown disease. It happened to be smallpox and came to be known as the plague of Galen, on account of the physician who described it. In the fourteen years that the scourge lasted, it is estimated to have killed from one-quarter to one-third of the Empire’s population and about 4 to 7 million in today’s Europe. Finally, in AD 252 either smallpox or a similar infectious disease struck the Empire again, sometimes killing more than 5,000 people a day. As years went by, other occurrences of such diseases took place, at least, in England (AD 444) and France (AD 580). However, the fact that only some cases are documented does not mean that there were not any others. It is thought that the precarious living conditions, together with famine and constant migration made pestilence an ordinary dweller in ancient times (Karlen 1996: 71-2, C. Smith 2008).
Two great plagues define the Middle Ages in epidemic terms: the plague of Justinian in the sixth century and the Black Death of the fourteenth. Both were decisive in that they produced significant havoc, covering the vast majority of what we know today as Europe, and marked the beginning and the end of the darkest period in human history. What is more, they also share the causative agent, a bacterium called
Yersinia Pestis. Without antibiotic treatment, obviously unknown at that time, the case-fatality ratio ranged between 30 to 60 percent (WHO 2008d) but the death toll could have reached an overwhelming 90 percent (C. Smith 2008). Probably due to the grim consequences that such a dreadful disease evokes in the western mind, the term “plague” covers nowadays any epidemic outbreak, dealing or not with the bubonic plague. As far as the plague of Justinian is concerned, it seems that, like the previous ones, it had originated in the heart of Africa, travelled down the Nile to the Mediterranean and reached Constantinople in 542. Once again, merchants and soldiers took it wherever trade routes stretched. The symptoms, faithfully described by the Byzantine historian Procopius, certainly differed from the diarrhoeas and pustules typical of smallpox (2007: 461-73). Although high fever was also a common affliction, the patients quickly developed swollen lymph glands in the armpits, groin and neck, which were called buboes; hence, the term bubonic. After the germ invaded the nervous system, causing generalised hallucinations, the sick individual would die of a failure of breathing by the fifth day. In its pneumonic form, the bacteria attacked the lungs and quickly multiplied until the whole internal tissue melted and was thrown out. People would normally die choking in their own vomit. In the city of Constantinople alone, about forty percent of the population died in the first bout of plague. In the following six years, it rampaged freely around the whole of Europe until disappearing suddenly. The plague came back frequently during the next two centuries, sometimes accompanied by outbreaks of other infectious diseases. By the beginning of the eighth century, Europe’s population had been cut in half (Karlen 1996: 75). Ultimately, then, Justinian’s dream of a new Roman empire crumbled under the power of epidemics and, the Dark Ages reigned over the western world.
Why bubonic plague vanished in such a mysterious way is still puzzling epidemiologists today. No one knows for sure if the germ naturally retreated to its animal reservoir, if it mutated to a more benign form or if it simply killed so many human hosts that the chain of infection was broken. Nevertheless, what is sure is that the weather improved considerably around the year 800 and that the surviving population lived scattered in the country. There was a period of relative calm, with the notable exception of some intermittent Viking raids. However, the awakening of crafts and commerce made cities grow and, thus, overpopulation again became a problem. Around the turn of the fourteenth century, cold weather, wheat-crop failures and recurrent cycles of famine, combined with the fierce Hundred Years War, brought about the ideal scenario for a new pandemic.
By the 1330s, plague began to spread from Central Asia to the Middle East following the caravan routes. In 1346, it reached the Crimean Port of Kaffa, which had been under siege by the Tartars and started decimating their troops. They had to leave, but catapulted the dead bodies of many plague-infected soldiers in their retreat. When the Genoese traders, who had been kept inside the city, left for Europe in the summer of 1347, they brought with them something more than oriental treasures. By the end of 1347, bubonic plague had already reached most Mediterranean ports and started spreading inland. It also mutated into the deadlier pneumonic form and by 1348 it had spread all over Europe. Since the concept of contagion was not understood at the time, pestilence was perceived as God’s punishment. In their generalised ignorance, people blamed the Jews, who were burnt by the thousands, and there were uncountable acts of contrition, including processions and flagellations. Some villages and towns lost their entire population, both by death and migration, and many important cities were reduced by a third to a half. An approximate toll requested by pope Clement VI showed
23,840,000 dead in Europe alone (Tuchman 1987: 93). That would mean that the western world had lost around one-third of its population (Wheelis 1999 and 2002: 971-4, ABC 2004).
After a hundred-year long transition, by the late fifteenth century the European nations started searching for new colonies that would ensure raw material for trade. In fact, plague had a decisive role in delaying the colonisation of the Americas since many nations were weakened and underwent hard times of recovery. Whereas smallpox had already become endemic in Europe by 1500, a condition that made it merely a childhood disease, its introduction into the New World by the colonisers caused a tremendous disturbance. The first major epidemic came in 1518, when one-third to one-half of the Arawaks in Hispaniola died of the disease. It swiftly jumped to Cuba and Puerto Rico. When Hernán Cortés sailed from Cuba to Mexico later that year, his ships carried the deadly disease to the Aztec lands. The natives received him as a God but strong differences forced him to leave very soon. He sought reinforcements in Cuba, where the smallpox epidemic was running its course, and returned to Tenochtitlán (today’s Mexico city) in 1521. About half of its original 300,000 inhabitants had already died before his soldiers conquered the city (Texas Department of State Health Services 2007).
Due to its long incubation period of about two weeks, smallpox was taken by the fleeing Aztecs to their Maya and Inca neighbours. In a matter of years, the pandemic covered the whole of South America and, arguably, an important part of the North. When Francisco Pizarro reached Cuzco, the Inca capital, in 1533 he found no effective resistance by the natives. Then came measles, influenza, typhoid and a great variety of other Old World diseases, which dramatically reduced the indigenous population. Although the estimates vary, the original Aztec population of about 25 million could have been shortened to 16.8 million, whereas the Incas lost 200,000 of their original 6 million population from 1524 to 1527 (Fenner et al. 1988: 236-7). Unquestionably, disease became the great conquistadores’
best ally.
As regards North America, French and English colonisers brought the same disease to the native people. Thus, tribes like the Huron, Iroquois, Cherokee, Catawba, Piegan and Omaha were halved in number during the seventeenth, eighteenth and nineteenth centuries (Fenner et al. 1988: 238). There were uncountable outbreaks, which made it very easy for the colonisers to impose their religion and social habits. Of course, the newcomers equally had to endure previously unknown diseases. Once again, the difficult living conditions in an inhospitable land, famine, disease and the tropical weather of most of the territories made an unexpected hell of the “promised land.” Likewise, there was a continuous interchange of infectious maladies from the Old World to the New and vice versa. Since communications drastically improved in the seventeenth and eighteenth centuries, the possibilities for new microbial disorder equally increased. It would be in the nineteenth century, with the advent of new medical treatment and a progressive urban settlement, that most infectious diseases became endemic.
However, a significant epidemic to be remembered, basically because of its literary transcendence, is the Great Plague of 1665. By that time, London was the world’s largest city and the poor living conditions, especially in densely crowded suburbs, eased the swift propagation of the disease. It was caused again by the Yersinia Pestis and had probably begun a year before in Turkey, reaching England by ship. Although those residents who could afford to leave the city, including the Royal family and the aristocracy, sought shelter in the countryside, the vast majority of lower social classes had to stay. A year later, coinciding with a sudden vanishing of the plague, London suffered a devastating fire which burnt most of the city down. It was believed that the fire stopped the disease even though the epidemic also faded from other big cities of the time, like Paris and Amsterdam, without the need for the flames. All in all, over 100,000 Londoners lost their lives in a single year (Garrett 1995: 238).
In the following centuries, similar epidemic disasters took place in Oceania and Australia. When the Europeans began colonising Australia in the late eighteenth century, the native tribes were devastated by epidemics of flu, smallpox, cholera and typhus. Likewise, whereas more than 20 percent of the aborigines of Hawaii and Fiji fell prey to measles between 1853 and 1874, the Maoris of New Zealand were reduced from 100,000 to 40,000 in the 1840s, 50s and 60s (Karlen 1996: 110). On the contrary, the colonisation of Africa, where most of the diseases brought by the explorers were already endemic, was tougher for the European than for the disease-hardened native.
In the twentieth century, undoubtedly one of the worst yet widely ignored plagues was the Spanish Flu pandemic of 1918. Despite its name, the disease seems to have had an Asian origin because most of the major mutations of the virus have taken place on that continent. These constant shifts are the virus’ main advantage against the defences of pigs, ducks, horses or human beings; the animals that are usually host to this agent. Thus, flu has been able to survive for thousands of years, returning cyclically in a different form that the immune system does not recognise. Of course, there have been other important flu epidemics in the past, which may have killed by the thousands. Also, so many people regularly catch the flu that the death toll, high as it can be, is not taken seriously. Moreover, those who die, generally from respiratory complications, are normally the sick or the elderly. Thus, human loss does not produce a significant social commotion and most of these outbreaks have gone unremarked.
In the spring of 1918, however, the healthy and the young also began to die. Of these, soldiers fighting in the war were the first to fall prey to the disease, which was thought to be a new kind of biological weapon. Yet, moving troops all over the world spread the flu and civilians soon fell ill. In many cities, everyday life was seriously affected by the collapse of the most essential services: hospitals were crowded, police and fire departments were left almost without operational officers, and most communal facilities like schools, libraries or theatres had to close down. About 15 million died in the fighting in World War I, which lasted four years. However, the Spanish Flu pandemic, which lasted two years, killed at least twice as many. There is an open controversy about the exact death toll worldwide, with some historians claiming twenty million and others reaching even forty or fifty.
In the early eighties, several cases of an infrequent kind of pneumonia started puzzling the medical authorities in big American cities like New York or San Francisco. A close study of subsequent cases denoted a strange collapse of the patients’ immune system, which induced generalised infections and cancers like Kaposi’s sarcoma or leukaemia. It was equally suspicious that most of the subjects were male homosexuals or drug-addicts. Instead of an understanding attitude, the social reaction was rather vehement, openly blaming the gay community for irresponsible behaviour which had its immediate results in this malady. In many cases, the sick were dismissed from their jobs and usually lost their social status. This only led to a widespread silence, which helped the disease spread swiftly amongst male homosexuals. However, the disease soon reached heterosexuals and haemophiliacs. As a result of international travel, either for business or pleasure, AIDS was taken to other parts of the world, so much so that by 1985, the disease was pandemic worldwide. There were countless theories about the origin of the disease, including rumours of conspiracy against blacks, extreme sexual practices amongst homosexuals, colonialist abuse of prostitution in Central Africa, and promising vaccines gone wrong (Grmek et al. 1990: 9, Kannabus and Allen 2007). While leading countries passed laws to protect the identities of the sick, the epidemic started killing people by the thousands, especially in the poorest regions of the globe. It was only when the disease touched all social classes, including some cinema and music stars in developed countries, that there was a general commitment and preventive measures were taken. By early 1988, as many as 129 countries had already reported their first case (Mann 1988).
Obviously, the HIV virus is not new to the human being. It seems that there could have been clinical incidents in the 1950s and the 1960s; not to mention others previously unrecorded or simply documented as of “unknown origin.” Yet, the 1980s outbreak was unprecedented for its virulence and ease of transmission. Since the virus has been present on Earth for thousands of years, the reason for such a late appearance must be found in the technical advances the human being had attained over the twentieth century. First of all, the breaking of an ecological barrier had taken man to virgin places in the ecosystem, where many unknown infectious agents lay dormant in their host. The open sexual behaviour in the sixties and seventies as well as the improvement in transport, had equally taken the virus from the first world to exotic countries via tourism and vice versa. Likewise, such a simple medical device as the syringe, had become an important vector of transmission because of its re-use in undeveloped countries. On the other hand, the fact that the HIV virus is not airborne should complicate its transmission significantly. Certainly, the HIV cannot compete with smallpox or influenza as it only infects through sexual intercourse, a skin scratch or by eating the raw meat of a sick animal. However, the efficiency of the HIV virus lies on its magnificent ability to mutate. It changes so quickly, that it may take several different forms inside the same host, thus easily dodging the immune system. Although the number of infections in developed countries has been falling lately thanks to preventive campaigns, AIDS has spread unstoppably in the Third World. By the beginning of the twenty-first century, the WHO admitted 30 to 40 million new infections and the epidemic seems far from subsiding.
Another great epidemic to remember took place in Surat. This Indian city in the state of Gujarat, suffered an outbreak of plague in 1994 which reminded the general public of the Black Death. Its origin must be found in the state of Maharashtra, 300 kilometres east of Bombay, which was shaken by a terrible earthquake only some weeks prior to the outbreak. The accumulation of rubbish and dead animals could have been the cause of the sudden growth in the rat population. Indian scientists warned of the uncontrolled reproduction of fleas and rats but the local administration did not take the words seriously. Many migrant workers from the surrounding area usually travel to Surat, an important port city 200 kilometres north of Bombay, to work in diamond cutting plants and textile mills. At least 80 cases of bubonic plague were reported in nearby villages by 26 September but the outbreak in Surat was of pneumonic plague. This would mean that the plague, which started in the Maharashtra state where it turned from bubonic to pneumonic, was imported into Surat by travellers in this second stage of the disease. Soon doctors were unable to treat the eight to ten new patients being admitted every hour to Surat’s hospital. The higher classes gathered the local supplies of tetracycline, an effective antibiotic to the plague bacteria. There were chaotic scenes of medical practitioners being attacked by the angry relatives of dying victims and troops were sent to the city to prevent infected people from leaving the zone. Yet, amongst the reigning anarchy, thousands of citizens abandoned the city. Barely a week later, an exodus of 600,000 people was confirmed (Ryan 1998: 111).
Whereas the Indian authorities refused to quarantine the city, claiming that the disease was under control, other cases appeared in different states. There was an international reaction and medical controls became compulsory for passengers travelling out of India. Moreover, doctors in Europe and America, where the disease was given special treatment by the media, routinely boarded Indian flights and it was recommended to exclude the country from the travel agenda. Meanwhile, by 29 September the infection had already spread to eight Indian states and the airborne condition of the pneumonic plague led epidemiologists to expect the worst. However, the infectious agent seemed relatively sensitive to tetracycline and the last plague case in Surat was declared on 11 October. The official statistics gather as many as 876 cases, although many may have gone unreported to the WHO (
Burns 1994, The New York Times 1994). The authorities of the country did not want to consider this outbreak as an epidemic, since the incidence was relatively “low.” Nevertheless, there are reputed voices claiming that, given the case of a sturdier germ, India and the world could have faced a renewed Black Death pandemic (Campbell and Hughes 1995).
A similar fear is felt about Ebola haemorrhagic fever on account of its dramatic symptoms. Although there have been several outbreaks recorded since 1976, three major events can be considered according to their influence on the biohazard narrative. The first one took place in Nzara, southern Sudan, between June and November 1976, with 284 people infected and 151 deaths. Later that same year the virus jumped to Yambuku, northern Zaire, infecting 318 people and killing 280. Finally, a new epidemic ravaged the Zairian city of Kikwit, 400 kilometres east of Kinshasa in 1995, leaving 254 people dead out of 315 infected (WHO 2008b, CDC 2008d).
The virus emerged surprisingly in mid 1976 in the Sudanese town of Nzara, in the south of the country close to the border with Zaire. The symptoms included headache, sore throat and nausea quickly developing into generalised pains, diarrhoea and bleeding to death in a matter of days. After the transfer of some patients to the hospital of Maridi, a larger town in the north, the illness also began to spread there. Most of the victims were located in Maridi, as the systematic reuse of hypodermic needles in this town’s hospital considerably helped the disease to advance there (WHO and International Study Team 1978).
An identical outbreak took place in the first days of September in Yambuku, a small town in the north of Zaire, only 825 kilometres southwest of Maridi. The centre of infection was also a hospital, where the virus killed 11 of the 17 staff (International Commission 1978). Many patients were also infected there and spread the disease around a region delimited by the river Ebola, a tributary of the Congo which gives its name to the pathogen. In spite of the geographic and timing proximity, the strains were proved to be of different origins. Since the death toll of this new strain approached 90 percent, the international authorities decided to isolate the Ebola region and send a research team. Although a major pandemic was expected when the fever reached Kinshasa, a city with a population of two million with air links to Europe, the epidemic vanished all of a sudden.
From then onwards, there were scattered cases in the 1980s until Ebola produced a new epidemic in Zaire in 1995. Despite the fact that the index case, a charcoal burner, had been infected the previous December, human to human transmission took place unnoticeably until the epidemic somehow found its way to Kikwit’s General Hospital, where it began its expansion in May (Sanchez et al. 1995). It seems that poor sanitary procedures once more became a chief cause of infection and hospital workers were the first to fall. Since the epidemic received full attention by the media, there was soon a state of international alert. Moreover, the publication of Richard Preston and Laurie Garrett’s bestsellers
The Hot Zone and The Coming Plague, respectively, equally contributed to the generalised hysteria. When the worst was feared, the disease retreated to its animal reservoir, questioning the ability of medical authorities to control this mysterious virus. After this last epidemic, there have been other outbreaks, mainly in Asia and Africa, where the virus probably has its natural reservoir. However, Ebola also appeared in research laboratories in Reston (Virginia), Alice (Texas) and Pennsylvania, United States of America, in 1989 and 1990. Many monkeys died and at least four persons contracted the disease, although none of them showed any symptoms. By June 2005, the WHO had reported nearly 1,900 cases resulting in almost 1,300 deaths (2008b).
Yet another disease which has been given much publicity lately is Bovine Spongiform Encephalopathy (BSE). Although it is transmissible only to cattle, there are also Transmissible Spongiform Encephalopathies (TSEs) affecting the human being, the best known of which is Creutzfeldt-Jakob Disease (CJD). TSE produces a spongy degeneration of the brain, which eventually leads to fatal neurological damage. There is controversy as to whether the agent causing BSE is a virus, an entity with nucleic acids carrying genetic information, or a prion, an agent basically made of a self-replicating protein. What is certain is that the agent is exceptionally sturdy, resisting very high or low temperature, even dodging the standards for pasteurisation and sterilisation. As regards CJD, about 85% of cases occur as sporadic disease, with only 5 to 15% of the patients developing the disease because of inherited mutations of the prion protein gene. (CDC 2009a). The transmission of the agent usually comes through contaminated surgical equipment from neurological transplants, although there are strong suspicions that the BSE can derive into a human TSE by the ingestion of tainted meat from sick cattle. Precisely, a new variant (vCJD) discovered in 1996 seems to be closely associated with contact with BSE-infected food. Although CJD largely affects the elderly, vCJD also acts on younger individuals and has a longer duration. The clinical features include depression, psychosis, unsteadiness leading to total immobility and inability to speak by death. Whereas the first patient to develop symptoms of the disease could be traced to early 1994, 147 human cases of vCJD were reported in the United Kingdom, 7 in France, and 1 each in Canada, Ireland, Italy, and the United States from 1995 to August 2004. It is interesting to note that “the patients from Canada, Ireland, and the United States had lived in the UK during a key exposure period of the UK population to the BSE agent” (CDC 2007c). Even if there is no evidence to predict the outcome of the disease, it seems feasible to expect a common presence of future TSE cases.
As of today, the human being is suffering the emergence of hitherto unknown germs and the re-emergence of old ones which have developed resistance to previously effective treatment. Whereas such words as AIDS or Ebola have already become familiar, there are still new diseases that are progressively entering our daily vocabulary. The uncontrolled concentration of people in large cities, international travel, poor sanitary conditions, alteration of the environment and constant abuse of antibiotics stand amongst the main causes for such an advance. Since 1973, at least 30 new germs have been reported to the WHO (2005a: 6) and the National Institute of Allergy and Infectious Diseases (2008b). A brief account includes:

  • Hepatitis C: About 3% of the world’s population seems to be infected with this virus identified in 1989. The patients are at risk of developing cirrhosis and/or cancer of the liver.

  • Sin nombre: First identified in 1993 in the southern United States, it is a flu-like virus of the family of the hantavirus. The disease preys on the lungs causing internal haemorrhages that can sometimes be lethal.

  • Influenza A (H5N1): A viral strain discovered in 1997, which is one of the causative agents of Avian Flu. It was first thought that it could cause the expected new influenza pandemic but the disease soon receded.

  • Legionella pneumophilia: A bacterium first identified in 1977 which causes severe pneumonia. The outbreaks of this disease are usually associated with air conditioning systems. Its detection explained the strange deaths of some legionnaires in a convention of veteran American soldiers in 1976.

  • Escherichia coli O157:H7: This bacterium, first identified in 1982, produces haemolytic uraemic syndrome and/or haemorrhagic colitis. Infection takes place through tainted or badly manipulated food.

  • Borrellia burgdorferi: First detected in the USA in 1982, this bacterium causes Lyme disease, a degenerating affliction ending in meningitis and mental derangement. It is endemic in North America and Europe and is transmitted to humans by ticks.

Moreover, certain other germs which have been under control until recently are developing a strong resistance to vaccines. Some of these are:

  • Cholera: In 1991, cholera re-appeared in South America, where the disease had been absent for over a century. As of today, the disease is present in most of Africa, Asia and South America.

  • Diphtheria: after the dissolution of former Soviet Union, this disease has affected some of its republics since 1994. Its advance is directly linked to failure of the immunisation programmes.

  • Yellow fever: Although there is an effective vaccine, its lack of use still allows frequent epidemics of this disease. It is present in 33 countries in Africa and eight in South America and there has been a persistent increase in the reported cases worldwide since 1980.


Works Cited:

Asimov, Isaac. Asimov’s Guide to the Bible: The Old Testament. New York: Avon Books, 1969 (1997).

Australian Broadcasting Corporation. “On the Trail of the Black Death.” Australian Broadcasting Corporation. 22 January 2004. Retrieved 9 July 2008.
http://www.abc.net.au/science/features/blackdeath/default.htm.

Burns, John F. “Calm Returns to Indian City hit by Plague.” The New York Times.
26 September 1994. Retrieved 9 July 2008.
http://query.nytimes.com/gst/fullpage.html?res=9F02E4DD133AF935A1575AC0A962958260&sec=&spon=&pagewanted=print.

Campbell, Grant L. and James M. Hughes. “Plague in India: A New Warning from
an Old Nemesis.” Annals of Internal Medicine. 15 January 1995. 122.2: 151-153.

Centers for Disease Control and Prevention. “CJD (Creutzfeldt-Jakob Disease, Classic).” Centers for Disease Control and Prevention. 2009a. Retrieved 9 July 2008.
http://www.cdc.gov/ncidod/dvrd/vcjd/epidemiology.htm.

-----. “Known Cases and Outbreaks of Ebola Hemorrhagic Fever in Chronological Order
.” Centers for Disease Control and Prevention. 2008d. Retrieved 11 October 2008. http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/ebola/ebolatable.htm.

-----. “vCJD (Variant Creutzfeldt-Jakob Disease).” Centers for Disease Control and
Prevention. 2007c. Retrieved 9 July 2008.
http://www.cdc.gov/ncidod/drvd/vcjd/epidemiology.htm.

Crosby, Alfred W. Epidemic and Peace, 1918. Westport: Greenwood Press, 1976.

Fenner, F., et al. Smallpox and its Eradication
. Geneva: World Health Organization,
1988. Retrieved 4 December 2008.
http://whqlibdoc.who.int/smallpox/9241561106.pdf.

Garrett, Laurie. The Coming Plague: Newly Emerging Diseases in a World out of Balance. New York: Penguin, 1995 (1994).

Grenke, Arthur. God, Greed and Genocide: The Holocaust through the Centuries.
Washington: New Academia Publishing, 2005.

Grmek, Mirko et al. History of AIDS: Emergence and Origin of a Modern Pandemic. Princeton: Princeton University Press, 1990.

International Commission. "Ebola haemorrhagic fever in Zaire, 1976." Bulletin of the World Health Organization. 1978. 56 (2): 271-293.

Kannabus, Annabel and Sarah Allen. “The Origins of HIV and the First Cases of AIDS.” Avert. 2007. Retrieved 9 July 2008.
http://www.avert.org/origin-aids-hiv.htm.

Karlen, Arno. Man and Microbes: Disease and Plagues in History and Modern
Times. New York: Touchtone 1996 (1995).

Mann, Jonathan. “The Global Picture of AIDS.” International AIDS Society. 1988.
Retrieved 9 July 2008.
http://www.aegis.com/conferences/iac/1988/K2.html.

National Institute of Allergy and Infectious Diseases. “Antimicrobial (Drug) Resistance.”
National Institute of Allergy and Infectious Diseases. 8 October 403 2008. Retrieved 24 December 2008. http://www3.niaid.nih.gov/topics/AntimicrobialResistance/default.htm.

Ouellette, Pierre. The Third Pandemic. London: Hodder and Stoughton, 1997 (1996).

Potter, C.W. “A History of Influenza.” Journal of Applied Microbiology. 2001: Vol. 91, No 4. 572-9.

Preston, Richard. The Hot Zone. New York: Anchor Books, 1995 (1994).

Procopius. History of the Wars. New York: Cosimo, 2007.

Ryan, Frank. Virus X. London: Harper Collins, 1998 (1996).

Sanchez et al. “Reemergence of Ebola Virus in Africa.” Emerging Infectious Diseases. 1995. 1. 3: 96-100.

Smith, Christine A. “Plague in the Ancient World: A Study from Thucydides to Justinian.” Loyola University New Orleans. 2008. Retrieved 9 July 2008.
http://www.loyno.edu/~history/journal/1996-7/Smith.html.

Texas Department of State Health Services. “History of Smallpox – Smallpox Through the Ages.” Texas Department of State Health Services. 30 March 2007. Retrieved 9 July 2008.
http://www.dshs.state.tx.us/preparedness/bt_public_history_smallpox.shtm.

The New York Times. “Surat: A Victim of its Open Sewers.” The New York Times. 25 September 1994. Retrieved on 19 December 2008.
http://query.nytimes.com/gst/fullpage.html?res=9F00E0DB123AF936A1575AC0A962958260.

Thucydides. History of the Peloponnesian War. London: Penguin Classics, 1972.

Tuchman, Barbara W. A Distant Mirror: The Calamitous 14th Century. New York: Ballantine Books, 1987 (1978).

Unaids. “2007 AIDS Epidemic Update.” Unaids. December 2007. Retrieved 9 July 2008.
http://data.unaids.org/pub/EPISlides/2007/2007_epiupdate_en.pdf.

Wheelis, Mark. “Biological Warfare at the 1346 Siege of Caffa.” Emerging Infectious Diseases. 26 July 2002. 8.9: 971-975. Retrieved 9 July 2008.
http://www.cdc.gov/ncidod/EID/vol8no9/pdf/01-0536.pdf.

-----. “Biological Warfare before 1914.” University of California. 1999. Retrieved 9 July 2008.
http://microbiology.ucdavis.edu/faculty/mwheelis/BW_before_1914.pdf.

World Health Organization.“Ebola Haemorrhagic Fever – Ebola Outbreak Chronology (fact sheet nº 103).” World Health Organization. 2008b. Retrieved December 2008.
http://www.who.int/mediacentre/factsheets/fs103/en/index1.html.

-----. “Plague.” World Health Organization. 2008d. Retrieved 12 May 2008.
http://www.who.int/mediacentre/factsheets/fs267/en/print.html.


-----. Regional Office for South-East Asia. “Combating Emerging Infectious Diseases.” World Health Organization. New Delhi: 2005a. Retrieved 19 December 2008.
http://www.searo.who.int/LinkFiles/Avian_Flu_combating_emerging_diseases.pdf.

----- and International Study Team. “Ebola Haemorrhagic Fever in Sudan, 1976.” Bulletin of the World Health Organization. 1978. 56. 2: 247-70.