A pandemic (from Greek pan "all" + demos "people") is an epidemic of infectious disease that is spreading through human populations across a large region; for instance a continent, or even worldwide. A widespread endemic disease that is stable in terms of how many people are getting sick from it is not a pandemic. Further, flu pandemics exclude seasonal flu. Throughout history there have been a number of pandemics, such as smallpox and tuberculosis. More recent pandemics include the HIV pandemic and the 2009 flu pandemic.
According to the World Health Organization (WHO), a pandemic can start when three conditions have been met:
* emergence of a disease new to a population;
* agents infect humans, causing serious illness; and
* agents spread easily and sustainably among humans.
A disease or condition is not a pandemic merely because it is widespread or kills many people; it must also be infectious. For instance, cancer is responsible for many deaths but is not considered a pandemic because the disease is not infectious or contagious.
2009 influenza A/H1N1
The 2009 outbreak of a new strain of Influenza A virus subtype H1N1 created concerns that a new pandemic was occurring. In the latter half of April, 2009, the World Health Organization's pandemic alert level was sequentially increased from three to five until the announcement on 11 June 2009 that the pandemic level had been raised to its highest level, level six.  This was the first pandemic on this level since 1968. Dr Margaret Chan, Director-General of the World Health Organization (WHO), gave a statement on 11 June 2009 confirming that the H1N1 strain was indeed a pandemic, having nearly 30,000 confirmed cases worldwide.
HIV and AIDS
HIV went directly from Africa to Haiti, then spread to the United States and much of the rest of the world beginning around 1969. HIV, the virus that causes AIDS, is currently a pandemic, with infection rates as high as 25% in southern and eastern Africa. In 2006 the HIV prevalence rate among pregnant women in South Africa was 29.1%. Effective education about safer sexual practices and bloodborne infection precautions training have helped to slow down infection rates in several African countries sponsoring national education programs. Infection rates are rising again in Asia and the Americas. AIDS could kill 31 million people in India and 18 million in China by 2025, according to projections by U.N. population researchers. AIDS death toll in Africa may reach 90-100 million by 2025.
Pandemics and notable epidemics through history
There have been a number of significant pandemics recorded in human history, generally zoonoses which came about with domestication of animals, such as influenza and tuberculosis. There have been a number of particularly significant epidemics that deserve mention above the "mere" destruction of cities:
* Plague of Athens, 430 BC. Typhoid fever killed a quarter of the Athenian troops, and a quarter of the population over four years. This disease fatally weakened the dominance of Athens, but the sheer virulence of the disease prevented its wider spread; i.e. it killed off its hosts at a rate faster than they could spread it. The exact cause of the plague was unknown for many years. In January 2006, researchers from the University of Athens analyzed teeth recovered from a mass grave underneath the city, and confirmed the presence of bacteria responsible for typhoid.
* Antonine Plague, 165–180. Possibly smallpox brought to the Italian peninsula by soldiers returning from the Near East; it killed a quarter of those infected, and up to five million in all. At the height of a second outbreak, the Plague of Cyprian (251–266), which may have been the same disease, 5,000 people a day were said to be dying in Rome.
* Plague of Justinian, from 541 to 750, was the first recorded outbreak of the bubonic plague. It started in Egypt, and reached Constantinople the following spring, killing (according to the Byzantine chronicler Procopius) 10,000 a day at its height, and perhaps 40% of the city's inhabitants. The plague went on to eliminate a quarter to a half of the human population that it struck throughout the known world.  It caused Europe's population to drop by around 50% between 550 and 700.
* Black Death, started 1300s. The total number of deaths worldwide is estimated at 75 million people. Eight hundred years after the last outbreak, the plague returned to Europe. Starting in Asia, the disease reached Mediterranean and western Europe in 1348 (possibly from Italian merchants fleeing fighting in the Crimea), and killed an estimated 20 to 30 million Europeans in six years; a third of the total population, and up to a half in the worst-affected urban areas. It was the first of a cycle of European plague epidemics that continued until the 18th century. During this period, more than 100 plague epidemics swept across Europe. In England, for example, epidemics would continue in 2- to 5-year cycles from 1361 to 1480. By the 1370s, England's population was reduced by 50%. The Great Plague of London of 1665–66 was the last major outbreak of the plague in England. The disease killed an estimated 100,000 people, 20% of London's population.
* Third Pandemic, started in China in the middle of the 19th century, spreading plague to all inhabited continents and killing 10 million people in India alone. During this pandemic, the United States saw its first case of plague in 1900 in San Francisco. Today, isolated cases of plague are still found in the western United States.
Encounters between European explorers and populations in the rest of the world often introduced local epidemics of extraordinary virulence. Disease killed the entire native (Guanches) population of the Canary Islands in the 16th century. Half the native population of Hispaniola in 1518 was killed by smallpox. Smallpox also ravaged Mexico in the 1520s, killing 150,000 in Tenochtitlán alone, including the emperor, and Peru in the 1530s, aiding the European conquerors. Measles killed a further two million Mexican natives in the 1600s. In 1618–1619, smallpox wiped out 90% of the Massachusetts Bay Native Americans. During the 1770s, smallpox killed at least 30% of the Pacific Northwest Native Americans. Smallpox epidemics in 1780–1782 and 1837–1838 brought devastation and drastic depopulation among the Plains Indians. Some believe that the death of up to 95% of the Native American population of the New World was caused by Old World diseases such as smallpox, measles, and influenza. Over the centuries, the Europeans had developed high degrees of immunity to these diseases, while the indigenous peoples had no such immunity.
Smallpox devastated the native population of Australia, killing around 50% of Indigenous Australians in the early years of British colonisation. It also killed many New Zealand Maori. As late as 1848–49, as many as 40,000 out of 150,000 Hawaiians are estimated to have died of measles, whooping cough and influenza. Introduced diseases, notably smallpox, nearly wiped out the native population of Easter Island. In 1875, measles killed over 40,000 Fijians, approximately one-third of the population. The disease decimated the Andamanese population. Ainu population decreased drastically in the 19th century, due in large part to infectious diseases brought by Japanese settlers pouring into Hokkaido.
Researchers concluded that syphilis was carried from the New World to Europe after Columbus' voyages. The findings suggested Europeans could have carried the nonvenereal tropical bacteria home, where the organisms may have mutated into a more deadly form in the different conditions of Europe. The disease was more frequently fatal than it is today. Syphilis was a major killer in Europe during the Renaissance. Between 1602 and 1796, the Dutch East India Company sent almost a million Europeans to work in the Asia. Ultimately, only less than one-third made their way back to Europe. The majority died of diseases. Disease killed more British soldiers in India than war. Between 1736 and 1834 only some 10% of East India Company's officers survived to take the final voyage home.
As early as 1803, the Spanish Crown organized a mission (the Balmis expedition) to transport the smallpox vaccine to the Spanish colonies, and establish mass vaccination programs there. By 1832, the federal government of the United States established a smallpox vaccination program for Native Americans. From the beginning of the 20th century onwards, the elimination or control of disease in tropical countries became a driving force for all colonial powers. The sleeping sickness epidemic in Africa was arrested due to mobile teams systematically screening millions of people at risk. In the 20th century, the world saw the biggest increase in its population in human history due to lessening of the mortality rate in many countries due to medical advances. The world population has grown from 1.6 billion in 1900 to an estimated 6.7 billion today.
* First cholera pandemic 1816-1826. Previously restricted to the Indian subcontinent, the pandemic began in Bengal, then spread across India by 1820. 10,000 British troops and countless Indians died during this pandemic. It extended as far as China, Indonesia (where more than 100,000 people succumbed on the island of Java alone) and the Caspian Sea before receding. Deaths in India between 1817 and 1860 are estimated to have exceeded 15 million persons. Another 23 million died between 1865 and 1917. Russian deaths during a similar time period exceeded 2 million.
* Second cholera pandemic 1829–1851. Reached Russia (see Cholera Riots), Hungary (about 100,000 deaths) and Germany in 1831, London in 1832 (more than 55,000 persons died in the United Kingdom), France, Canada (Ontario), and United States (New York) in the same year, and the Pacific coast of North America by 1834. A two-year outbreak began in England and Wales in 1848 and claimed 52,000 lives. It is believed that over 150,000 Americans died of cholera between 1832 and 1849.
* Third pandemic 1852–1860. Mainly affected Russia, with over a million deaths. In 1852, cholera spread east to Indonesia and later invaded China and Japan in 1854. The Philippines were infected in 1858 and Korea in 1859. In 1859, an outbreak in Bengal once again led to the transmission of the disease to Iran, Iraq, Arabia and Russia.
* Fourth pandemic 1863–1875. Spread mostly in Europe and Africa. At least 30,000 of the 90,000 Mecca pilgrims fell victim to the disease. Cholera claimed 90,000 lives in Russia in 1866.
* In 1866, there was an outbreak in North America. It killed some 50,000 Americans.
* Fifth pandemic 1881-1896. The 1883-1887 epidemic cost 250,000 lives in Europe and at least 50,000 in Americas. Cholera claimed 267,890 lives in Russia (1892); 120,000 in Spain; 90,000 in Japan and 60,000 in Persia.
* In 1892, cholera contaminated the water supply of Hamburg, Germany, and caused 8606 deaths.
* Sixth pandemic 1899–1923. Had little effect in Europe because of advances in public health, but Russia was badly affected again (more than 500,000 people dying of cholera during the first quarter of the 20th century). The sixth pandemic killed more than 800,000 in India. The 1902-1904 cholera epidemic claimed over 200,000 lives in the Philippines.
* Seventh pandemic 1962-66. Began in Indonesia, called El Tor after the strain, and reached Bangladesh in 1963, India in 1964, and the USSR in 1966.
* The Greek physician Hippocrates, the "Father of Medicine", first described influenza in 412 BC.
* The first influenza pandemic was recorded in 1580 and since then influenza pandemics occurred every 10 to 30 years.
* Influenza pandemics in 1729-1730, 1732-1733, 1781-1782, 1830, 1833-1834, 1847-1848.
* The "Asiatic Flu", 1889–1890, was first reported in May 1889 in Bukhara, Uzbekistan. By October, it had reached Tomsk and the Caucasus. It rapidly spread west and hit North America in December 1889, South America in February–April 1890, India in February-March 1890, and Australia in March–April 1890. It was purportedly caused by the H2N8 type of flu virus. It had a very high attack and mortality rate. About 1 million people died in this pandemic."
* The "Spanish flu", 1918–1919. First identified early in March 1918 in US troops training at Camp Funston, Kansas. By October 1918, it had spread to become a world-wide pandemic on all continents, and eventually infected an estimated one third of the world's population (or ≈500 million persons). Unusually deadly and virulent, it ended nearly as quickly as it began, vanishing completely within 18 months. In six months, some 50 million were dead; some estimates put the total of those killed worldwide at over twice that number. An estimated 17 million died in India, 675,000 in the United States and 200,000 in the UK. The virus was recently reconstructed by scientists at the CDC studying remains preserved by the Alaskan permafrost. They identified it as a type of H1N1 virus.
* The "Asian Flu", 1957–58. An H2N2 virus caused about 70,000 deaths in the United States. First identified in China in late February 1957, the Asian flu spread to the United States by June 1957. It caused about 2 million deaths globally.
* The "Hong Kong Flu", 1968–69. An H3N2 caused about 34,000 deaths in the United States. This virus was first detected in Hong Kong in early 1968, and spread to the United States later that year. This pandemic of 1968 and 1969 killed an estimated one million people worldwide. Influenza A (H3N2) viruses still circulate today.
Typhus is sometimes called "camp fever" because of its pattern of flaring up in times of strife. (It is also known as "gaol fever" and "ship fever", for its habits of spreading wildly in cramped quarters, such as jails and ships.) Emerging during the Crusades, it had its first impact in Europe in 1489, in Spain. During fighting between the Christian Spaniards and the Muslims in Granada, the Spanish lost 3,000 to war casualties, and 20,000 to typhus. In 1528, the French lost 18,000 troops in Italy, and lost supremacy in Italy to the Spanish. In 1542, 30,000 soldiers died of typhus while fighting the Ottomans in the Balkans.
During the Thirty Years' War (1618–1648), an estimated 8 million Germans were wiped out by bubonic plague and typhus fever. The disease also played a major role in the destruction of Napoleon's Grande Armée in Russia in 1812. Felix Markham thinks that 450,000 soldiers crossed the Neman on 25 June 1812, of whom less than 40,000 recrossed in anything like a recognizable military formation. In early 1813 Napoleon raised a new army of 500,000 to replace his Russian losses. In the campaign of that year over 219,000 of Napoleon's soldiers were to die of typhus. Typhus played a major factor in the Irish Potato Famine. During the World War I, typhus epidemics have killed over 150,000 in Serbia. There were about 25 million infections and 3 million deaths from epidemic typhus in Russia from 1918 to 1922. Typhus also killed numerous prisoners in the Nazi concentration camps and Soviet prisoner of war camps during World War II. More than 3.5 million Soviet POWs died in the Nazi custody out of 5.7 million.
Smallpox is a highly contagious disease caused by the Variola virus. The disease killed an estimated 400,000 Europeans per year during the closing years of the 18th century. During the 20th century, it is estimated that smallpox was responsible for 300–500 million deaths. As recently as early 1950s an estimated 50 million cases of smallpox occurred in the world each year. After successful vaccination campaigns throughout the 19th and 20th centuries, the WHO certified the eradication of smallpox in December 1979. To this day, smallpox is the only human infectious disease to have been completely eradicated.
Historically, measles was very prevalent throughout the world, as it is highly contagious. According to the National Immunization Program, 90% of people were infected with measles by age 15. Before the vaccine was introduced in 1963, there were an estimated 3-4 million cases in the U.S. each year. In roughly the last 150 years, measles has been estimated to have killed about 200 million people worldwide. In 2000 alone, measles killed some 777,000 worldwide. There were some 40 million cases of measles globally that year.
Measles is an endemic disease, meaning that it has been continually present in a community, and many people develop resistance. In populations that have not been exposed to measles, exposure to a new disease can be devastating. In 1529, a measles outbreak in Cuba killed two-thirds of the natives who had previously survived smallpox. The disease had ravaged Mexico, Central America, and the Inca civilization.
One–third of the world's current population has been infected with Mycobacterium tuberculosis, and new infections occur at a rate of one per second. About one in ten of these latent infections will eventually progress to active disease, which, if left untreated, kills more than half of its victims. Annually, 8 million people become ill with tuberculosis, and 2 million people die from the disease worldwide. In the 19th century, tuberculosis killed an estimated one-quarter of the adult population of Europe; and by 1918 one in six deaths in France were still caused by TB. By the late 19th century, 70 to 90% of the urban populations of Europe and North America were infected with M. tuberculosis, and about 40% of working-class deaths in cities were from TB. During the 20th century, tuberculosis killed approximately 100 million people. TB is still one of the most important health problems in the developing world.
Leprosy, also known as Hansen’s Disease, is caused by a bacillus, Mycobacterium leprae. It is a chronic disease with an incubation period of up to five years. Since 1985, 15 million people worldwide have been cured of leprosy. In 2002, 763,917 new cases were detected. It is estimated that there are between one and two million people permanently disabled because of leprosy.
Historically, leprosy has affected mankind since at least 600 BC, and was well-recognized in the civilizations of ancient China, Egypt and India. During the High Middle Ages, Western Europe witnessed an unprecedented outbreak of leprosy. Numerous leprosaria, or leper hospitals, sprang up in the Middle Ages; Matthew Paris estimated that in the early 13th century there were 19,000 across Europe.
Malaria is widespread in tropical and subtropical regions, including parts of the Americas, Asia, and Africa. Each year, there are approximately 350–500 million cases of malaria. Drug resistance poses a growing problem in the treatment of malaria in the 21st century, since resistance is now common against all classes of antimalarial drugs, with the exception of the artemisinins.
Malaria was once common in most of Europe and North America, where it is now for all purposes non-existent. Malaria may have contributed to the decline of the Roman Empire. The disease became known as "Roman fever". Plasmodium falciparum became a real threat to colonists and indigenous people alike when it was introduced into the Americas along with the slave trade. Malaria devastated the Jamestown colony and regularly ravaged the South and Midwest. By 1830 it had reached the Pacific Northwest. During the American Civil War, there were over 1.2 million cases of malaria among soldiers of both sides. The southern U.S. continued to be afflicted with millions of cases of malaria into the 1930s.
Yellow fever has been a source of several devastating epidemics. Cities as far north as New York, Philadelphia, and Boston were hit with epidemics. In 1793, the largest yellow fever epidemic in U.S. history killed as many as 5,000 people in Philadelphia—roughly 10% of the population. About half of the residents had fled the city, including President George Washington. Approximately 300,000 people are believed to have died from yellow fever in Spain during the 19th century. In colonial times, West Africa became known as "the white man's grave" because of malaria and yellow fever.
There are also a number of unknown diseases that were extremely serious but have now vanished, so the etiology of these diseases cannot be established. The cause of English Sweat in 16th-century England, which struck people down in an instant and was more greatly feared than even the bubonic plague, is still unknown.
Concern about possible future pandemics
Viral hemorrhagic fevers
Some Viral Hemorrhagic Fever causing agents like Lassa fever, Rift Valley fever, Marburg virus, Ebola virus and Bolivian hemorrhagic fever are highly contagious and deadly diseases, with the theoretical potential to become pandemics. Their ability to spread efficiently enough to cause a pandemic is limited, however, as transmission of these viruses requires close contact with the infected vector, and the vector only has a short time before death or serious illness. Furthermore, the short time between a vector becoming infectious and the onset of symptoms allows medical professionals to quickly quarantine vectors, and prevent them from carrying the pathogen elsewhere. Genetic mutations could occur, which could elevate their potential for causing widespread harm; thus close observation by contagious disease specialists is merited.
Antibiotic-resistant microorganisms, sometimes referred to as "superbugs", may contribute to the re-emergence of diseases which are currently well-controlled. For example, cases of tuberculosis that are resistant to traditionally effective treatments remain a cause of great concern to health professionals. Every year, nearly half a million new cases of multidrug-resistant tuberculosis (MDR-TB) are estimated to occur worldwide. After India, China has the highest rate of multidrug-resistant TB. The World Health Organization (WHO) reports that approximately 50 million people worldwide are infected with MDR TB, with 79 percent of those cases resistant to three or more antibiotics. In 2005, 124 cases of MDR TB were reported in the United States. Extensively drug-resistant tuberculosis (XDR TB) was identified in Africa in 2006, and subsequently discovered to exist in 49 countries, including the United States. About 40,000 new cases of XDR-TB emerge every year, the WHO estimates.
The plague bacterium Yersinia pestis could develop drug-resistance and become a major health threat. Plague epidemics have occurred throughout human history, causing over 200 million deaths worldwide. The ability to resist many of the antibiotics used against plague has been found so far in only a single case of the disease in Madagascar.
In the past 20 years, common bacteria including Staphylococcus aureus, Serratia marcescens and Enterococcus, have developed resistance to various antibiotics such as vancomycin, as well as whole classes of antibiotics, such as the aminoglycosides and cephalosporins. Antibiotic-resistant organisms have become an important cause of healthcare-associated (nosocomial) infections (HAI). In addition, infections caused by community-acquired strains of methicillin-resistant Staphylococcus aureus (MRSA) in otherwise healthy individuals have become more frequent in recent years.
Inappropriate antibiotic treatment and overuse of antibiotics have been a contributing factor to the emergence of resistant bacteria. The problem is further exacerbated by self-prescribing of antibiotics by individuals without the guidelines of a qualified clinician and the non-therapeutic use of antibiotics as growth promoters in agriculture.
In 2003, there were concerns that Severe Acute Respiratory Syndrome (SARS), a new and highly contagious form of atypical pneumonia, might become pandemic. It is caused by a coronavirus dubbed SARS-CoV. Rapid action by national and international health authorities such as the World Health Organization helped to slow transmission and eventually broke the chain of transmission. That ended the localized epidemics before they could become a pandemic. However, the disease has not been eradicated. It could re-emerge. This warrants monitoring and reporting of suspicious cases of atypical pneumonia.
Wild aquatic birds are the natural hosts for a range of influenza A viruses. Occasionally, viruses are transmitted from these species to other species, and may then cause outbreaks in domestic poultry or (rarely) give rise to a human pandemic. 
H5N1 (Avian Flu)
In February 2004, avian influenza virus was detected in birds in Vietnam, increasing fears of the emergence of new variant strains. It is feared that if the avian influenza virus combines with a human influenza virus (in a bird or a human), the new subtype created could be both highly contagious and highly lethal in humans. Such a subtype could cause a global influenza pandemic, similar to the Spanish Flu, or the lower mortality pandemics such as the Asian Flu and the Hong Kong Flu.
From October 2004 to February 2005, some 3,700 test kits of the 1957 Asian Flu virus were accidentally spread around the world from a lab in the US.
In May 2005, scientists urgently call nations to prepare for a global influenza pandemic that could strike as much as 20% of the world's population.
In October 2005, cases of the avian flu (the deadly strain H5N1) were identified in Turkey. EU Health Commissioner Markos Kyprianou said: "We have received now confirmation that the virus found in Turkey is an avian flu H5N1 virus. There is a direct relationship with viruses found in Russia, Mongolia and China." Cases of bird flu were also identified shortly thereafter in Romania, and then Greece. Possible cases of the virus have also been found in Croatia, Bulgaria and the United Kingdom.
By November 2007, numerous confirmed cases of the H5N1 strain had been identified across Europe . However, by the end of October only 59 people had died as a result of H5N1 which was atypical of previous influenza pandemics.
Avian flu cannot yet be categorized as a "pandemic", because the virus cannot yet cause sustained and efficient human-to-human transmission. Cases so far are recognized to have been transmitted from bird to human, but as of December 2006 there have been very few (if any) cases of proven human-to-human transmission. Regular influenza viruses establish infection by attaching to receptors in the throat and lungs, but the avian influenza virus can only attach to receptors located deep in the lungs of humans, requiring close, prolonged contact with infected patients, and thus limiting person-to-person transmission.
In 1346, the bodies of Mongol warriors who had died of plague were thrown over the walls of the besieged Crimean city of Kaffa (now Theodosia). After a protracted siege, during which the Mongol army under Jani Beg was suffering the disease, they catapulted the infected corpses over the city walls to infect the inhabitants. It has been speculated that this operation may have been responsible for the advent of the Black Death in Europe.
The Native American population was decimated after contact with the Old World due to the introduction of many different fatal diseases. There is, however, only one documented case of germ warfare, involving British commander Jeffrey Amherst and Swiss-British officer Colonel Henry Bouquet, whose correspondence included a reference to the idea of giving smallpox-infected blankets to Indians as part of an incident known as Pontiac's Rebellion which occurred during the Siege of Fort Pitt (1763) late in the French and Indian War. It is uncertain whether this documented British attempt successfully infected the Indians.
During the Sino-Japanese War (1937-1945), Unit 731 of the Imperial Japanese Army conducted human experimentation on thousands, mostly Chinese. In military campaigns, the Japanese army used biological weapons on Chinese soldiers and civilians. Plague fleas, infected clothing, and infected supplies encased in bombs were dropped on various targets. The resulting cholera, anthrax, and plague were estimated to have killed around 400,000 Chinese civilians.
Diseases considered for weaponization, or known to be weaponized include anthrax, ebola, Marburg virus, plague, cholera, typhus, Rocky Mountain spotted fever, tularemia, brucellosis, Q fever, machupo, Coccidioides mycosis, Glanders, Melioidosis, Shigella, Psittacosis, Japanese B encephalitis, Rift Valley fever, yellow fever, and smallpox.
Spores of weaponized anthrax were accidentally released from a military facility near the Soviet closed city of Sverdlovsk in 1979. The Sverdlovsk anthrax leak is sometimes called "biological Chernobyl". China possibly suffered a serious accident at one of its biological weapons plants in the late 1980s. The Soviets suspected that two separate epidemics of hemorrhagic fever that swept the region in the late 1980s were caused by an accident in a lab where Chinese scientists were weaponizing viral diseases. In January 2009, an Al-Qaeda training camp in Algeria had been wiped out by the plague, killing approximately 40 Islamic extremists. Experts said that the group was developing biological weapons..
1. "Avian influenza frequently asked questions" (in en). World Health Organization. December 5, 2005. http://www.who.int/csr/disease/avian_influenza/avian_faqs/en... Retrieved 2009-02-13. "A pandemic can start when three conditions have been met: a new influenza virus subtype emerges; it infects humans, causing serious illness; and it spreads easily and sustainably among humans."
2. "AWHO 'declares swine flu pandemic'". BBC News. June 11, 2009.
3. The virus reached the U.S. by way of Haiti, genetic study shows.. Los Angeles Times. October 30, 2007.
4. The South African Department of Health Study, 2006
5. AIDS Toll May Reach 100 Million in Africa. Washington Post. June 4, 2006.
6. Aids could kill 90 million Africans, says UN
7. "Ancient Athenian Plague Proves to Be Typhoid". Scientific American. January 25, 2006.
8. Past pandemics that ravaged Europe. BBC News, November 7. 2005
9. Cambridge Catalogue page "Plague and the End of Antiquity"
10. Quotes from book "Plague and the End of Antiquity" Lester K. Little, ed., Plague and the End of Antiquity: The Pandemic of 541-750, Cambridge, 2006. ISBN 0-521-84639-0
11. "Plague, Plague Information, Black Death Facts, News, Photos – National Geographic". Science.nationalgeographic.com. http://science.nationalgeographic.com/science/health-and-hum... Retrieved 2008-11-03.
12. New MOL Archaeology monograph: Black Death cemetery. Archaeology at the Museum of London.
13. Death on a Grand Scale. MedHunters.
14. Stéphane Barry and Norbert Gualde, in L'Histoire n° 310, June 2006, pp.45–46, say "between one-third and two-thirds"; Robert Gottfried (1983). "Black Death" in Dictionary of the Middle Ages, volume 2, pp.257–67, says "between 25 and 45 percent".
15. Plague - LoveToKnow 1911. 1911encyclopedia.org.
16. "A List of National Epidemics of Plague in England 1348-1665"
17. Jo Revill. "Black Death blamed on man, not rats | UK news | The Observer". The Observer. http://www.guardian.co.uk/uk/2004/may/16/health.books. Retrieved 2008-11-03.
18. "Texas Department of State Health Services, History of Plague". Dshs.state.tx.us. http://www.dshs.state.tx.us/preparedness/bt_public_history_p... Retrieved 2008-11-03.
19. "BBC – History – Black Death". bbc.co.uk. http://www.bbc.co.uk/history/british/middle_ages/black_09.sh... Retrieved 2008-11-03.
20. The Great Plague of London, 1665. The Harvard University Library, Open Collections Program: Contagion.
21. Plague. World Health Organization.
22. Bubonic plague hits San Francisco 1900 - 1909. A Science Odyssey. Public Broadcasting Service (PBS).
23. Human Plague -- United States, 1993-1994, Centers for Disease Control and Prevention
24. Smallpox: Eradicating the Scourge
25. Smallpox The Fight to Eradicate a Global Scourge, David A. Koplow
26. Greg Lange,"Smallpox epidemic ravages Native Americans on the northwest coast of North America in the 1770s", 23 Jan 2003, HistoryLink.org, Online Encyclopedia of Washington State History, accessed 2 Jun 2008
27. Houston CS, Houston S (March 2000). "The first smallpox epidemic on the Canadian Plains: In the fur-traders' words". Can J Infect Dis 11 (2): 112–5. PMID 18159275.
28. The Story Of... Smallpox – and other Deadly Eurasian Germs
29. Stacy Goodling, "Effects of European Diseases on the Inhabitants of the New World"
30. Smallpox Through History
31. New Zealand Historical Perspective
32. How did Easter Island's ancient statues lead to the destruction of an entire ecosystem?, The Independent
33. Fiji School of Medicine
34. Measles hits rare Andaman tribe. BBC News. May 16, 2006.
35. Meeting the First Inhabitants, TIMEasia.com, 21 August 2000
36. Genetic Study Bolsters Columbus Link to Syphilis, New York Times, January 15, 2008
37. Columbus May Have Brought Syphilis to Europe, LiveScience
38. Nomination VOC archives for Memory of the World Register (English)
39. "Sahib: The British Soldier in India, 1750-1914 by Richard Holmes"
40. Dr. Francisco de Balmis and his Mission of Mercy, Society of Philippine Heath History
41. Lewis Cass and the Politics of Disease: The Indian Vaccination Act of 1832
42. Conquest and Disease or Colonialism and Health?, Gresham College | Lectures and Events
43. WHO Media centre (2001). Fact sheet N°259: African trypanosomiasis or sleeping sickness. http://www.who.int/mediacentre/factsheets/fs259/en/index.htm...
44. The Origins of African Population Growth, by John Iliffe, The Journal of African HistoryVol. 30, No. 1 (1989), pp. 165-169
45. World Population Clock - Worldometers
46. Cholera- Biological Weapons
47. The 1832 Cholera Epidemic in New York State
48. Asiatic Cholera Pandemic of 1826-37
49. The Cholera Epidemic Years in the United States
50. Cholera's seven pandemics, cbc.ca, December 2, 2008
51. a b The 1832 Cholera Epidemic in New York State - Page 2. By G. William Beardslee
52. Asiatic Cholera Pandemic of 1846-63 . UCLA School of Public Health.
53. Eastern European Plagues and Epidemics 1300-1918
54. Cholera - LoveToKnow 1911
55. "The cholera in Spain". New York Times. 1890-06-20. http://query.nytimes.com/gst/abstract.html?res=9E05EED7123BE... Retrieved 2008-12-08.
56. Barry, John M. (2004). The Great Influenza: The Epic Story of the Greatest Plague in History. Viking Penguin. ISBN 0-670-89473-7.
57. cholera :: Seven pandemics, Britannica Online Encyclopedia
58. 1900s: The Epidemic Years, Society of Philippine Health History
59. 50 Years of Influenza Surveillance. World Health Organization.
60. "Pandemic Flu". Department of Health and Social Security.
61. Beveridge, W.I.B. (1977) Influenza: The Last Great Plague: An Unfinished Story of Discovery, New York: Prodist. ISBN 0-88202-118-4.
62. Potter, C.W. (October 2001). "A History of Influenza". Journal of Applied Microbiology 91 (4): 572–579. doi:10.1046/j.1365-2672.2001.01492.x. http://www.blackwell-synergy.com/doi/abs/10.1046/j.1365-2672... Retrieved 2006-08-20.
63. "Bird flu timeline: A history of influenza from 412 BC – AD 2006". NaturalNews.
64. CIDRAP article Pandemic Influenza Last updated 29 May 2008
65. a b Taubenberger JK, Morens DM (January 2006). "1918 Influenza: the mother of all pandemics". Emerg Infect Dis (Centers for Disease Control and Prevention (CDC)) 12 (1). http://www.cdc.gov/ncidod/eid/vol12no01/05-0979.htm.
66. Spanish flu, ScienceDaily
67. Pandemics and Pandemic Threats since 1900. U.S. Department of Health & Human Services
68. Q&A: Swine flu. BBC News. April 27, 2009.
69. "World health group issues alert Mexican president tries to isolate those with swine flu". Associate Press. April 25, 2009. http://www.jsonline.com/news/usandworld/43705182.html. Retrieved 2009-04-26.
70. War and Pestilence. TIME. April 29, 1940
71. See a large copy of the chart here: http://www.adept-plm.com/Newsletter/NapoleonsMarch.htm, but discussed at length in Edward Tufte, The Visual Display of Quantitative Information (London: Graphics Press, 1992)
72. a b Joseph M. Conlon. "The historical impact of epidemic typhus" (PDF). http://entomology.montana.edu/historybug/TYPHUS-Conlon.pdf.
73. Soviet Prisoners of War: Forgotten Nazi Victims of World War II By Jonathan Nor, TheHistoryNet
74. Smallpox and Vaccinia. National Center for Biotechnology Information.
75. "UC Davis Magazine, Summer 2006: Epidemics on the Horizon". http://ucdavismagazine.ucdavis.edu/issues/su06/feature_1b.ht... Retrieved 2008-01-03.
76. How Poxviruses Such As Smallpox Evade The Immune System, ScienceDaily, February 1, 2008
77. "Smallpox". WHO Factsheet. Retrieved on 2007-09-22.
78. De Cock KM (2001). "(Book Review) The Eradication of Smallpox: Edward Jenner and The First and Only Eradication of a Human Infectious Disease". Nature Medicine 7: 15–6. doi:10.1038/83283. http://www.nature.com/nm/journal/v7/n1/full/nm0101_15b.html.
79. Center for Disease Control & National Immunization Program. Measles History, article online 2001. Available from http://www.cdc.gov.nip/diseases/measles/history.htm
80. a b Torrey EF and Yolken RH. 2005. Their bugs are worse than their bite. Washington Post, April 3, p. B01.
81. Stein CE, Birmingham M, Kurian M, Duclos P, Strebel P (May 2003). "The global burden of measles in the year 2000—a model that uses country-specific indicators". J. Infect. Dis. 187 (Suppl 1): S8–14. doi:10.1086/368114. PMID 12721886.
82. Man and Microbes: Disease and Plagues in History and Modern Times; by Arno Karlen
83. "Measles and Small Pox as an Allied Army of the Conquistadors of America" by Carlos Ruvalcaba, translated by Theresa M. Betz in "Encounters" (Double Issue No. 5-6, pp. 44-45)
84. World Health Organization (WHO). Tuberculosis Fact sheet N°104 - Global and regional incidence. March 2006, Retrieved on 6 October 2006.
85. Centers for Disease Control. Fact Sheet: Tuberculosis in the United States. 17 March 2005, Retrieved on 6 October 2006.
86. Multidrug-Resistant Tuberculosis. Centers for Disease Control and Prevention.
87. Tuberculosis in Europe and North America, 1800–1922. The Harvard University Library, Open Collections Program: Contagion.
88. Immune responses to tuberculosis in developing countries: implications for new vaccines. Nature Reviews Immunology 5, 661-667 (August 2005).
89. Leprosy 'could pose new threat'. BBC News. April 3, 2007.
90. Leprosy (Hansen's Disease).Centers for Disease Control and Prevention (CDC).
91. "Leprosy". WHO. http://www.who.int/mediacentre/factsheets/fs101/en/. Retrieved 2007-08-22.
92. "Medieval leprosy reconsidered". International Social Science Review, Spring-Summer, 2006, by Timothy S. Miller, Rachel Smith-Savage.
93. Boldsen JL (February 2005). "Leprosy and mortality in the Medieval Danish village of Tirup". Am. J. Phys. Anthropol. 126 (2): 159–68. doi:10.1002/ajpa.20085. PMID 15386293. http://www3.interscience.wiley.com/journal/108564968/abstrac...
94. "Leprosy". Catholic Encyclopedia. New York: Robert Appleton Company. 1913. http://en.wikisource.org/wiki/Catholic_Encyclopedia_(1913)/L...
95. Malaria Facts. Centers for Disease Control and Prevention.
96. White NJ (April 2004). "Antimalarial drug resistance". J. Clin. Invest. 113 (8): 1084–92. doi:10.1172/JCI21682. PMID 15085184.
97. Vector- and Rodent-Borne Diseases in Europe and North America. Norman G. Gratz. World Health Organization, Geneva.
98. DNA clues to malaria in ancient Rome. BBC News. February 20, 2001.
99. "Malaria and Rome". Robert Sallares. ABC.net.au. January 29, 2003.
100. "The Changing World of Pacific Northwest Indians". Center for the Study of the Pacific Northwest, University of Washington.
101. "A Brief History of Malaria"
102. Malaria. By Michael Finkel. National Geographic Magazine.
103. Yellow Fever - LoveToKnow 1911.
104. Arnebeck, Bob (January 30, 2008). "A Short History of Yellow Fever in the US". Benjamin Rush, Yellow Fever and the Birth of Modern Medicine. http://www.geocities.com/bobarnebeck/history.html. Retrieved 04-12-2008.
105. Tiger mosquitoes and the history of yellow fever and dengue in Spain.
106. Africa's Nations Start to Be TheirBrothers' Keepers. The New York Times, October 15, 1995.
107. Health ministers to accelerate efforts against drug-resistant TB. World Health Organization.
108. Bill Gates joins Chinese government in tackling TB 'timebomb'. Guardian.co.uk. April 1, 2009
109. Tuberculosis: A new pandemic?. CNN.com
110. Drug-resistant plague a 'major threat', say scientists, SciDev.Net
111. Researchers sound the alarm: the multidrug resistance of the plague bacillus could spread. Pasteur.fr
112. Larson E (2007). "Community factors in the development of antibiotic resistance.". Annu Rev Public Health 28: 435–47. doi:10.1146/annurev.publhealth.28.021406.144020. PMID 17094768.
113. Klenk et al. (2008). "Avian Influenza: Molecular Mechanisms of Pathogenesis and Host Range". Animal Viruses: Molecular Biology. Caister Academic Press. ISBN 978-1-904455-22-6.
114. Kawaoka Y (editor). (2006). Influenza Virology: Current Topics. Caister Academic Press. ISBN 978-1-904455-06-6. http://www.horizonpress.com/flu.
115. MacKenzie D (13 April 2005). "Pandemic-causing 'Asian flu' accidentally released". New Scientist. http://www.newscientist.com/article/dn7261.
116. "Flu pandemic 'could hit 20% of world's population'". guardian.co.uk. 25 May 2005. http://www.guardian.co.uk/world/2005/may/25/birdflu.
117. "Bird flu is confirmed in Greece". BBC NEWS. 17 October 2005. http://news.bbc.co.uk/1/hi/world/europe/4348404.stm.
118. "Bird Flu Map". BBC NEWS. http://news.bbc.co.uk/1/shared/spl/hi/world/05/bird_flu_map/...
119. Wheelis M (September 2002). "Biological warfare at the 1346 siege of Caffa". Emerging Infect. Dis. 8 (9): 971–5. PMID 12194776. http://www.cdc.gov/ncidod/EID/vol8no9/01-0536.htm.
120. Diamond, Jared (1997). Guns, Germs, and Steel: The Fates of Human Societies. W.W. Norton & Company. ISBN 0-393-03891-2.
121. Dixon, Never Come to Peace, 152–55; McConnell, A Country Between, 195–96; Dowd, War under Heaven, 190. For historians who believe the attempt at infection was successful, see Nester, Haughty Conquerors", 112; Jennings, Empire of Fortune, 447–48.
122. Christopher Hudson (2 March 2007). "Doctors of Depravity". Daily Mail. http://www.dailymail.co.uk/pages/live/articles/news/news.htm...
123. a b Ken Alibek and S. Handelman. Biohazard: The Chilling True Story of the Largest Covert Biological Weapons Program in the World - Told from Inside by the Man Who Ran it. 1999. Delta (2000) ISBN 0-385-33496-6 .
124. William J Broad, Soviet Defector Says China Had Accident at a Germ Plant, New York Times, April 5, 1999
125. Al-Qaeda cell killed by Black Death 'was developing biological weapons' Telegraph. January 20, 2009.