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How Did Humans Eradicate Smallpox?

How Did Humans Eradicate Smallpox?

On 9 December 1979, the eradication of smallpox was certified by a panel of scientists following what the World Health Organisation describes as “one of the most successful collaborative public health initiatives in history.”

Origin and spread

The earliest evidence of smallpox dates back to the ancient Egyptians. Mummies from the period known as the New Kingdom of Egypt, between the 16th and 11th centuries BC, have been found to have skin lesions similar to those caused by the disease.

Trade and travel spread the disease through Asia during the early centuries of the Common Era, and returning crusaders hastened its proliferation across Europe during the 11th and 12th centuries.

The subsequent arrival of Europeans in the Americas in the 16th century brought catastrophe to the native populations, who possessed absolutely no immunity to the disease. Historians suggest up to 90% of the indigenous populations of North and South America may have been wiped out – a scale of devastation far beyond the capacity of the European invaders.

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Royal victims

Smallpox killed about a third of those it infected. Mary II of England and Louis XV of France were just two of its high profile victims. Who knows how the history of England might have been altered had it claimed another, Elizabeth I, who contracted the disease in 1562. She bore its scars for the rest of her life, concealing them with white lead paint.

Elizabeth I was one of the notable royal victims of smallpox, hiding the scars with heavy makeup. Credit: National Portrait Gallery, London

During the 10th century a process was developed to fight the disease. It began in China and India and was called variolation. It involved inoculating healthy people with mild doses of smallpox in order to build up their immunity.

This procedure carried a serious risk that subjects might develop the disease in earnest and die as a result. However it achieved some success and by the 17th century the practice had spread to Europe and the Americas.

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Jenner’s theory

The major turning point came in 1796. Edward Jenner, a British scientist, heard of a theory that milkmaids who suffered from the relatively mild virus known as cowpox never contracted smallpox.

He put the idea to the test. Taking a sample of pus from a milkmaid suffering with cowpox, Jenner inserted it into an incision in the arm of a young boy. He then inoculated the boy with smallpox and found that he was immune to the disease. The theory was correct. Jenner had produced the first ever successful vaccine.

Use of the vaccine gradually spread. Around the world, countries began vaccinating their populations en masse.

Edward Jenner pioneered smallpox vaccination. Credit: Pan American Health Organisation

The road to eradication

In 1959 the World Health Assembly resolved to eradicate the disease entirely. By this time smallpox had been all but wiped out in Europe and North America but countries remained susceptible to outbreaks caused by individuals bringing the disease back from abroad.

The last natural case of smallpox was in Somalia in 1977. Ali Maow Maalin was working in a hospital when he contracted the disease, developing a fever on 22 October. He was diagnosed and made a full recovery. Unfortunately Maalin died of malaria in 2013 while working with the polio eradication campaign.

The last death from smallpox occurred in Birmingham, England in 1978. Janet Parker worked at the Birmingham University Medical School. Her office was located one floor above the Medical Microbiology Department where research into smallpox was underway. Somehow Janet contracted the disease, and died on 11 September.

On 9 December, 1979 the eradication of smallpox was certified by a panel of scientists, having carried out a global study. The following year, on 8 May, their findings were officially endorsed by the World Health Assembly.

Image: A cartoon highlighting the concerns about Jenner’s vaccine. it shows patients actually turning into cows! ©LibraryofCongress


Global Smallpox Eradication

1980 witnessed the fulfilment of a goal that many had considered impossible. At the recommendation of an independent commission of experts, the World Health Organization&rsquos (WHO) Health Assembly announced the global eradication of smallpox. It was a momentous occasion. In the view of many, with good reason, this was the greatest achievement of global public health in the twentieth century.

However, the passage of time seems to have taken some shine off the accomplishment in some quarters. Speeches and writings dealing with problems faced with current immunisation programmes argue, all too often, that smallpox eradication was easily achieved. According to this interpretation of events, the problems faced by the &lsquosmallpox warriors&rsquo were relatively straightforward as the disease did not have animal hosts.

For further information, please contact Professor Sanjoy Bhattacharya, Director of the Centre for Global Health Histories at the University of York.

Some commentators also argue, quite simplistically, that the work was based merely a strategy of searching for cases, containing infective individuals and vaccinating their immediate contacts with efficacious vaccines. These arguments are becoming increasingly commonplace as a series of subjective histories are beginning to be used by global funding agencies and scientists in their employ to justify dramatic increases in funding for new immunisation programmes targeted at specific disease.

These trends make it all the more important to come up with a rounded history of smallpox eradication that does not reduce the success of a complex global programme to the ideas and actions of a handful of individuals, and the impact of a supposedly uniform and stable vaccine technology.

A diversity of challenges

&zwnjThe situation was always more complicated throughout the course of a long-drawn out global smallpox eradication programme. Although it was announced in the late 1950s, the programme really only took off a decade later (after the completion of a series of successful campaigns across West Africa). Notably, its constituent activities took a further ten years to complete in a situation where the South Asian sub-continent and the Horn of Africa threw up a series of unexpected challenges. The mere presence of technological developments &mdash such as the introduction of heat stable freeze dried vaccines, and the so-called bifurcated needle that contributed to vaccinal economy and safety&mdash did not guarantee smallpox eradication. Human agency was an important determinant. Indeed, significant efforts had to be made by programme managers within the WHO and national governments to convince field officials to embrace new ideas and technologies. Notably, despite these efforts at persuasion, some people remained indifferent to the calls for the introductions of new operational methods and vaccinal products, choosing to stick to older procedures that they were more comfortable with and often regarded as being more reliable.

&zwnjOther challenges continued to afflict the campaign as well. Some sections of the target population opposed vaccination, which led to delays in projects in some areas and introduced time-consuming negotiations in others. There were, after all, limits to how much pressure the &lsquosmallpox warriors&rsquo could impose on local politicians, junior governmental officials and civilians diplomatic niceties could not be dispensed with altogether and international workers remained wary about stoking violent civilian resistance. Force, when it was used, could create lasting resentment, which was recognised as being strategically unhelpful in the longer term.

Other factors also created difficulties for the global effort at smallpox eradication. Support from within the WHO frameworks in Geneva and the Regional Offices remained inconstant, and often caused serious financial difficulties for those working in the field. These challenges were only overcome in the 1970s with the assistance provided by a range of donors. Help was provided by sources as diverse as the Swedish and Danish International Development Agencies, the Indian and Bangladeshi governments, and, not least, the Tata industrial consortium in India. To make matters worse &mdash and these trends remained visible right till the end of the campaign &mdash some officials associated to national and local governments continued to oppose the eradication goal, often simply because they considered it misguided and damaging to the vitality of general healthcare facilities. In addition, competing health and financial priorities, alternative epidemiological understandings of smallpox causation and control, and a variety of professional and personal jealousies proved damaging. This stoked doubts amongst bureaucratic and civilian constituencies, which translated into episodes where assistance was refused to teams of &lsquosmallpox warriors&rsquo.

Celebrating diversity and variation in practice

There were many positive aspects to the global smallpox eradication programme as well. A large number of participants cherish the internationalism that characterised it. For many, the campaign allowed a context in which cold war rivalries gradually dissipated, as several officials from the USA, the erstwhile USSR and countries allied to each of these countries learnt to trust each other. It is also worth remembering that many national workers regarded their participation in the project as a career highlight, allowing an intense and productive association with WHO frameworks. This attitude is well represented by the care and pride with which many officials have preserved certificates thanking them for their involvement in the eradication programme. There can be little doubt that there was goodwill amongst many &lsquosmallpox warriors&rsquo, despite differences in nationality, education, race, gender and age. For many young officials, participation in such a global programme led to new career paths, with international and government agencies, non-government organisations, universities and charities. A shared goal of saving lives drew many people together in the 1970s and ultimately gave rise to projects such as the Expanded Programme on Immunisation, whose components are credited for reducing levels of infantile mortality around the world by many observers.

However, all these positives should not be allowed to cloak important intricacies in operational strategy, especially as these are sometimes downplayed or ignored in celebratory treatises. The global smallpox eradication programme, which was composed of several national chapters linked by a series of international accords, was always marked by variations in official and civilian attitudes. Participants had differing visions about the efficacy of plans, and teams were composed of workers with dissimilar levels of ability and commitment. The contours of these attitudinal variations changed over time and place, as there were shifts in the composition of teams and their interactions with various constituencies in national territories and their locales.

Significantly, the transfer of ideas about the best means of eradicating smallpox did not flow in one direction. Indeed, the most effective campaigns were generally those that were based on a proactive exchange of ideas between field personnel of different ranks and backgrounds. For this reason, regular meetings between international workers and national counterparts were regarded as being a crucial component of the programme in the 1970s. Many international workers were also able to play another important role &mdashconduits for locally garnered information, which would otherwise have been ignored by those at the apex of national governing structures. Notably, WHO representatives were often able to put forward ideas presented by junior medical and paramedical staff who were in touch with the social, political and economic realities of specific regions this frequently ensured that such input was not summarily rejected. The multi-directional flow of ideas &mdash and the resulting impact on field policies &mdash is not always recognised or analysed by chroniclers of smallpox eradication. These trends are worthy of sensitive and in-depth study so that we are better able to present the many complexities characterising international, national and local vaccination campaigns.

A spirit of collaboration, in the widest sense, allowed the achievement of the impossible. So, as a magnificent achievement in public health co-operation is celebrated, care should be taken to avoid reducing all successes to the contributions made by a few individuals associated to specific institutions. These people and organisations could not, on their own, have stamped out smallpox all over the world. Different health agencies worked with each other, with one stepping up to fill the breach whenever another&rsquos strength was denuded by constant toil and required time to recover its vitality. Seen from this perspective, a complex association of institutions and people led to the stamping out of variola in its natural form it is of paramount importance that we do not forget the contributions of the many people who contributed to the triumph. As Donald A. Henderson and others deeply involved in running this most remarkable and complicated public health programme remind us in a series of lectures and interviews, smallpox eradication would have been impossible without the dedication of a huge number of individuals. It is imperative that we do not forget that a vast majority of these people were drawn from the countries where the final battles against the variola virus were concluded. Many more voices need to be remembered and recorded, before they are lost to posterity. But, that is a job for future historians, for whom there remains a lot to study and better understand, not least as efforts continue to be made to learn from past experiences.


Smallpox is the only human disease to be eradicated – here’s how the world achieved it

This blog post draws on data and research discussed in our entry on Smallpox, which we published simultaneously with this blog post and where you find much more detail on the disease, its global history, and the vaccine that ended the disease.

Until today smallpox is the only human disease that has been successfully eradicated. 1 The eradication of smallpox is therefore a major success story for global health for several reasons: it was a disease that was endemic – and caused high mortality rates – across all continents but was also crucial to advances in the field of immunology as the smallpox vaccine was the first successful vaccine to ever be invented.

Smallpox is an infectious disease caused by the variola virus which infects exclusively humans. No treatment existed so once you caught smallpox nothing could be done but let the infection run its course. Smallpox was responsible for millions of deaths in the past. The chart below illustrates this by visualizing the deaths due to smallpox as a share of all deaths in London from 1629 to 1902. In peak years, almost every fifth death was caused by smallpox! Death rates were similarly high in other European countries.

In 1796, British surgeon Edward Jenner invented the smallpox vaccine, the world’s first vaccine against any disease. The dramatic decrease in smallpox deaths at the turn of the 19th century can be credited to his invention. Our entry’s section on how eradication was achieved, we discuss how Jenner discovered the virus that protected people against smallpox infections and how he initially struggled to spread the word about it.

Click to open interactive version

Global declines in smallpox cases

Thanks to the widespread roll out of Jenner’s vaccine across Europe and North America, smallpox was almost entirely eliminated in these regions by the first half of the 20th century. When the WHO launched its ‘Intensified Smallpox Eradication Program’ in 1966, most cases were therefore restricted to South America, Africa and Asia – especially India –, where the vaccine’s rollout had been slower and patchier.

The map below shows the number of smallpox cases by country – note the large differences in color brackets that were necessary to accommodate China and India’s large case numbers. Large-scale vaccination campaigns however meant that the remaining countries saw rapid declines in the late 1960s and early 1970s. You can use the ‘play’ button at the bottom right of the map to see how case numbers evolved over time and by clicking on individual countries, you can see their reported smallpox cases in a line chart.

Click to open interactive version

Eradication of smallpox by country

The more severe type of smallpox, caused by the variola major virus strand, was eradicated in 1975 in Bangladesh, shortly after India had been declared smallpox-free that same year. The variola minor virus, which caused a weaker form of smallpox infections, was still in circulation on the African continent, though. The last smallpox infection worldwide was documented in October 1977 in Somalia.

The map below shows the year in which smallpox ceased to be endemic for each country, with each decade corresponding to a different color.

Click to open interactive version

Global eradication

The chart below illustrates how deadly the disease once was. Just the reported number of smallpox cases between 1920 and 1978 already amounted to 11.6 million cases and that number was certainly smaller than the actual number of cases, although we don’t know by how much. We discuss estimates of this discrepancy in the data quality section of our entry.

In the 1950s and 60s the number of reported cases started to decline and by the end of the 1970s there were no cases reported anymore. The WHO search teams continued to search for more smallpox cases but, with the exception of two tragic cases in Birmingham in the United Kingdom due to a laboratory accident in 1978, 2 found none. Therefore, in 1980 the World Health Organization declared smallpox the first – and so far only human – disease to be eradicated globally.

Imagine what this means, a disease that was once common across the world and caused millions of deaths and disfigured the faces of even more simply does not exist anymore.

For more detailed information on the characteristics of smallpox, its global history, and the vaccine that ended the disease, visit our entry on Smallpox that we published simultaneously with this blog post.

Click to open interactive version

Endnotes

While one other disease, Rinderpest, has also been eradicated, smallpox is the only one that infected humans. Rinderpest ‘only’ infected animals, predominantly cattle and buffalo, and was declared eradicated in 2011.

Lockley, M. (2016) The smallpox death that locked down Birmingham could have been avoided. Birmingham Mail. Retrieved 19 July 2018 from here.

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The data produced by third parties and made available by Our World in Data is subject to the license terms from the original third-party authors. We will always indicate the original source of the data in our documentation, so you should always check the license of any such third-party data before use and redistribution.


History of Smallpox

The history of smallpox holds a unique place in medicine. One of the deadliest diseases known to humans, it is also the only human disease to have been eradicated by vaccination.

Symptoms of a typical smallpox infection began with a fever and lethargy about two weeks after exposure to the Variola virus. Headache, sore throat, and vomiting were common as well. In a few days, a raised rash appeared on the face and body, and sores formed inside the mouth, throat, and nose. Fluid-filled pustules would develop and expand, in some cases joining together and covering large areas of skin. In about the third week of illness, scabs formed and separated from the skin.

About 30% of cases ended in death, typically in the second week of infection. Most survivors had some degree of permanent scarring, which could be extensive. Other deformities could result, such as loss of lip, nose, and ear tissue. Blindness could occur as a result of corneal scarring.

Smallpox was spread by close contact with the sores or respiratory droplets of an infected person. Contaminated bedding or clothing could also spread the disease. A patient remained infectious until the last scab separated from the skin.

Smallpox plagued human populations for thousands of years. Researchers who examined the mummy of Egyptian pharaoh Ramses V (died 1157 BCE) observed scarring similar to that from smallpox on his remains. Ancient Sanskrit medical texts, dating from about 1500 BCE, describe a smallpox-like illness. Smallpox was likely present in Europe by about 300 CE.

Some estimates indicate that 20th-century worldwide deaths from smallpox numbered more than 300 million. The last known case of wild smallpox occurred in Somalia in 1977.

HIGHLIGHTS

Edward Jenner learned from a milkmaid that she believed herself protected from smallpox because she had caught cowpox from a cow.

The World Health Organization launched the Intensified Smallpox Eradication Programme, which eventually led to the disappearance of smallpox.

Andrew Jackson (1767-1845), future U.S. president, contracted smallpox at age 14 while being held prisoner by the British during the War of Independence.

Watch the progression of a case of smallpox in a young man who survived the disease.

Ali Maow Maalin, a worker at a hospital in Somalia, contracted the last case of naturally occurring smallpox.


Smallpox: How the Deadliest Disease in History Was Eradicated

If you were to watch a split-screen broadcast with global weather on one side and world politics on the other, you could easily conclude that we are doomed. Prodigious storms and killer heat waves announce the arrival of human-induced climate change, with more disasters to come as the planet warms and ecosystems collapse.

But right-wing populism is rising faster than the oceans, sinking efforts to combat this and other global crises. Meanwhile, President Donald Trump keeps tweeting that climate change is fake news. Very bad!

And yet we humans have also shown that we can overcome even our most daunting problems. Exhibit A is our victory over smallpox, perhaps the most feared pathogen of all time.

Ancient scourge

The smallpox virus probably "jumped" from camels or other domesticated animals to people some 3,000 years ago, striking everyone from Chinese peasants to Egyptian pharaohs.

The highly contagious disease caused fever and tremors in infants, killing them even before the tell-tale rash broke out. Thousands of tiny pox appeared on the faces and hands of older victims, leaving many dead and many more disfigured.

By the medieval period, healers across Asia had learned to insert pus from a victim's pox into the shoulder or thigh of a healthy but at-risk person. Known as inoculation, this procedure carried a two to five percent death rate&mdashmuch lower than full-blown smallpox&mdashand usually brought on a mild case that still conferred lifelong immunity.

Europeans unwittingly gave the virus new life by delivering infected African slaves to hellish mines near Columbus's landing spot on Hispaniola (Haiti and Dominican Republic) in 1518. From the islands, smallpox spread to the mainland, enabling the ruthless conquistadors to topple vast civilizations who had no natural immunity to "spotted death."

The apocalypse that followed has no parallel in recorded history. In repeated outbreaks all over the Americas, smallpox killed up to 90 percent of some Indigenous peoples. Among the worst hit were the Salish of Vancouver&mdashtheir traditions speak of a "fearful dragon" whose hot breath fell upon the children, burning their skin into sores.

From inoculation to vaccination

But people fought back. Around 1720, Europeans and colonial Americans learned about inoculation from Ottoman and West African sources. During an outbreak in Boston, the Rev. Cotton Mather urged everyone to embrace this new method&mdashand to ignore the bigots who dismissed it as "negro" or "Mahometan" (Islamic) sorcery.

Many used this technique for darker purposes. Wealthy planters on the British island of Barbados imposed near-universal inoculation by 1750 because they wanted to keep their slaves in the sugar fields. In the 1760s, British commanders protected their own troops and then spread the monster disease to native enemies. They probably did the same to rebel colonists in Boston a decade later.

Nonetheless, men and women with open minds worked to combat smallpox, the common enemy. They shared ideas with researchers from enemy nations and insisted that medical progress in service to humanity had no price and no borders.

The big breakthrough came in 1796, when Dr. Edward Jenner observed that English milkmaids never caught smallpox. He scraped the "milker's nodules" on their hands and applied the infected material&mdasha related virus known as cowpox or vaccinia&mdashto his patients. Vaccination was born.

Despite his fear and loathing of England, U.S. President Thomas Jefferson wrote to Jenner with thanks on behalf of "the whole human family."

Throughout the 19th and 20th centuries, wealthy countries vaccinated their people with increasing regularity. The U.S. even had a National Vaccine Institute until parsimonious congressmen killed it in 1822. Poorer countries in Africa and the Caribbean suffered longer, even though they had pioneered inoculation.

The lingering threat

In 1966, four years after the last case in Canada, the WHO resolved to wipe smallpox off the Earth. This remarkable project succeeded in large part because of the close co-operation of the U.S. and the Soviet Union&mdashdespite the Cold War. Humanity has now been smallpox-free for more than 40 years. We no longer live in fear of another outbreak, nor recall the ghastly sight of a child in its clutches.

The downside is that most of us no longer have any immunity against this cruel foe, making us just as vulnerable as the first Americans were five centuries ago.

Officially, the virus only exists in two high-security laboratories in the U.S. and Russia. Because smallpox is stable in laboratory environments, however, old stocks from the days of inoculation may be hiding. Bioterrorists could weaponize such active matter.

If that were to happen, we would need new drugs such as tecovirimat, just approved by the U.S. government. We'd also require the intelligent use of vaccine stocks and a massive international effort to contain the outbreaks and the panic they'd spread. We'd need to overcome the inevitable resistance of anti-government and anti-science reactionaries.

All of that may seem impossible in 2018.

That's why we need to remember our first triumph over smallpox as proof of our ingenuity and resilience, not to mention our capacity to work together for the health and happiness of our species.

Steven M Opal is a Research Scientist and Clinical Professor of Medicine at the Alpert Medical School, Brown University and J.M. Opal is Associate Professor of History and Chair, History and Classical Studies at McGill University

This article is republished from The Conversation under a Creative Commons license. Read the original article.


Symptoms

Smallpox is caused by the variola virus. There are four different types of the virus, according to the U.S. Food and Drug Administration, and the symptoms they cause vary in severity.

The virus is transmitted through the air in moisture droplets spread by sneezing, coughing and talking. It can also be spread by touching things that an infected person has touched, although catching the virus that way isn't as common.

The incubation period for smallpox is generally 12 to 14 days, which means a person may not show signs of infection for around two weeks, according to the Mayo Clinic. Once the incubation period is over, the infected person will have symptoms of fever, headache, backache, abdominal pain and a general feeling of being unwell. Lesions will also form in the mucous membranes of the nose and mouth.

A discrete and characteristic rash also appears. The rash first forms on the face, hands, forearms, mouth and throat before spreading to the trunk during the second week of illness. As the illness progresses, the rashes become more pronounced and blisters develop. Eight to nine days later, the blisters scab over.

A person is contagious as long as the rash is present once all the scabs have separated, they're no longer contagious, said Dr. Robert J. Leggiadro, a physician and professor at Villanova University in Pennsylvania.


Bacteria preserves foods

Thousands of years ago, humans learned to use lactic acid bacteria - for the production of yoghurt, kefir, sourdough bread and cheese. Raw milk warmed to 20 degrees Celsius is heaven for bacteria: Within 10 hours, the milk will go sour. Milk fermented with the help of bacteria, however, can stay edible for much longer.

Bacteria, viruses, mold: life-threatening yet indispensible


Disease Eradication

When a disease stops circulating in a region, it’s considered eliminated in that region. Polio, for example, was eliminated in the United States by 1979 after widespread vaccination efforts.

If a particular disease is eliminated worldwide, it’s considered eradicated. To date, only one infectious disease that affects humans has been eradicated.* In 1980, after decades of efforts by the World Health Organization, the World Health Assembly endorsed a statement declaring smallpox eradicated. Coordinated efforts rid the world of a disease that had once killed up to 35% of its victims and left others scarred or blind.

Smallpox eradication was accomplished with a combination of focused surveillance—quickly identifying new smallpox cases—and ring vaccination. “Ring vaccination” meant that anyone who could have been exposed to a smallpox patient was tracked down and vaccinated as quickly as possible, effectively corralling the disease and preventing its further spread. The last case of wild smallpox occurred in Somalia in 1977.

Smallpox was a good candidate for eradication for several reasons. First, the disease is highly visible: smallpox patients develop a rash that is easily recognized. In addition, the time from exposure to the initial appearance of symptoms is fairly short, so that the disease usually can’t spread very far before it’s noticed. Workers from the World Health Organization found smallpox patients in outlying areas by displaying pictures of people with the smallpox rash and asking if anyone nearby had a similar rash.

Second, only humans can transmit and catch smallpox. Some diseases have an animal reservoir, meaning they can infect other species besides humans. Yellow fever, for example, infects humans, but can also infect monkeys. If a mosquito capable of spreading yellow fever bites an infected monkey, the mosquito can then give the disease to humans. So even if the entire population of the planet could somehow be vaccinated against yellow fever, its eradication could not be guaranteed. The disease could still be circulating among monkeys, and it could re-emerge if human immunity ever waned. (The discovery of an animal reservoir for yellow fever was in fact what derailed a yellow fever eradication effort in the early 1900s.) Smallpox, however, can infect only humans. In effect, aside from the human population, it has nowhere to hide.

Equally important is the ability to protect individuals against infection. People who survived smallpox naturally developed lifelong immunity against future infection. For everyone else, vaccination was highly effective. WHO trained vaccinators quickly, and they could immunize large groups of people in a short time.

The eradication of smallpox raised hopes that the same could be accomplished for other diseases, with many named as possibilities: polio, mumps, and dracunculiasis (Guinea worm disease), among others. Malaria has also been considered, and its incidence has been reduced drastically in many countries. It presents a challenge to the traditional idea of eradication, however, in that having malaria does not result in lifelong immunity against it (as smallpox and many other diseases do). It is possible to fall ill with malaria many times, although individuals may develop partial immunity after multiple attacks. In addition, although promising steps have been made, no effective malaria vaccine yet exists.

Other diseases present additional challenges. Polio, though it has been reduced or eliminated in most countries through widespread vaccination, still circulates in some areas because (among other reasons) many cases do not present easily recognizable symptoms. As a result, an infected person can remain unnoticed, yet still spread the virus to others. Measles is problematic in a similar way: although the disease results in a highly visible rash, a significant period of time elapses between exposure to the virus and the development of the rash. Patients become contagious before the rash appears, and can spread the virus before anyone realizes they have the disease.

Guinea worm disease is likely on the verge of eradication. Only 30 cases were reported in 2017, from just 2 countries (Chad [15 cases], Ethiopia [15 cases]). [1] Though the case count increased from 2016, experts are still hopeful about the possibility of eradication. The Carter Center International Task Force for Disease Eradication has declared six additional diseases as potentially eradicable: lymphatic filariasis (Elephantiasis), polio, measles, mumps, rubella, and pork tapeworm. [2]

*Rinderpest, a disease that affected livestock, has also been eradicated, largely due to vaccination.


The Spread and Eradication of Smallpox

Traces of smallpox pustules found on the head of a 3,000-year-old mummy of the Pharaoh Ramses V. By G. Elliot Smith, Public Domain.

A written description of a disease that clearly resembles smallpox appears in China

In China, people appealed to the god Yo Hoa Long for protection from smallpox. Image taken from Recherche sur les Superstitions en Chine (Research on Chinese Superstitions) by Henri Dore, Shanghai, 1911-1920. Bibliotheque nationale de France.

Increased trade with China and Korea introduces smallpox into Japan.

Drawing of a woman defeating the &ldquosmallpox demon&rdquo by wearing red. A myth commonly believed around the world advocated that red light would cure smallpox. In Japan, families who fell sick with smallpox set up shrines to the &ldquosmallpox demon&rdquo in their homes with the hope they would appease the demon and be cured. By Sensai Eitaku (鮮斎永濯, Japanese, *1843, &dagger1890) &ndash scanned from ISBN 978-4-309-76096-4., Public Domain]

Smallpox is widespread in India. Arab expansion spreads smallpox into northern Africa, Spain, and Portugal.

Figurine of Indian smallpox goddess Shitala Mata worshipped in northern India. She was considered both the cause and cure of smallpox disease. Symbolically, she represents the importance of good hygiene in people&rsquos health and motivates worshipers to keep their surroundings clean. Photo courtesy of the National Library of Medicine.

Smallpox spreads to Asia Minor, the area of present-day Turkey.

The map shows the Ottoman Empire in 1801, which then extended from Turkey (Anatolia) to Greece, Hungary, Bulgaria, Romania, as well as northern Africa and parts of Middle East. Smallpox is thought to arrive to the area from Asia through major trade routes, like the Silk Road.

Entrance into Europe

Crusades further contribute to the spread of smallpox in Europe with the European Christians moving to and from the Middle East during the next two centuries.

Smallpox moves north

Population expansion and more frequent travel renders smallpox endemic in previously unaffected Central and North Europe, with severe epidemics occurring as far as Iceland.

Smallpox is widespread in many European countries, and Portuguese expeditions to African west coast and new trade routes with eastern parts of Africa introduce the disease into West Africa.

Statue of Shapona, the West African god of smallpox. Smallpox was thought to be a disease forced upon humans due to Shapona&rsquos &ldquodivine displeasure,&rdquo and formal worship of the god of smallpox was highly controlled by specific priests in charge of shrines to the god. People believed that the priests themselves were capable of causing smallpox outbreaks. Even though the British colonial rulers banned the worship of Shapona in 1907, worship of the deity continued. Source: CDC, photo credit James Gathany.

European colonization and the African slave trade import smallpox into the Caribbean and Central and South America.

Illustration by the Franciscan missionary Bernardino de Sahagun who wrote detailed accounts of the Aztec history during his life there from 1545 until his death in 1590 into 12 books entitled &ldquoGeneral History of the Things of New Spain.&rdquo Introduction of smallpox into Mexico by the Spanish around 1520 was one of the factors that led to the demise of Aztec Empire. Scanned from (2009) Viruses, Plagues, and History: Past, Present and Future, Oxford University Press, USA, p. 60. Public Domain.

Variolation&mdasha process of grinding up dried smallpox scabs from a smallpox patient and inhaling them or scratching them into an arm of an uninfected person&mdashis being used in China (inhalation technique) and India (cutaneous technique) to control smallpox.

A container from Ethiopia used to store the powdery variolation material, which was produced by grinding up dried smallpox scabs taken from a smallpox patient. Source: CDC, photo credit Brian Holloway.

Increased use of variolation

Variolation (cutaneous technique) is a widespread method for preventing smallpox in the Ottoman Empire (former Asia Minor, present-day Turkey) and North Africa.

Smallpox spreads into North America

European colonization imports smallpox into North America.

Variolation is introduced into England by Lady Mary Wortley Montagu, the wife of the British ambassador to Turkey.

Lady Mary Wortley Montagu, the wife of the British ambassador, learned about variolation during their appointment in Turkey. A survivor of smallpox herself, she had both of her children variolated and was the foremost person responsible for the introduction of the technique to England.

In 1796, Edward Jenner, an English doctor, shows the effectiveness of previous cowpox infection in protecting people from smallpox, forming the basis for vaccination.

Edward Jenner (1749&ndash1823). Photo courtesy of the National Library of Medicine.

Smallpox is widespread in Africa, Asia, and South America in the early 1900s, while Europe and North America have smallpox largely under control through the use of mass vaccination.

The map shows the worldwide distribution of smallpox and the countries in which it was endemic in 1945. Source: CDC, photo credit Dr. Michael Schwartz.

After a global eradication campaign that lasted more than 20 years, the 33rd World Health Assembly declares the world free of smallpox in 1980.

WHO poster commemorating the eradication of smallpox in October 1979, which was later officially endorsed by the 33rd World Health Assembly on May 8, 1980. Courtesy of WHO.


SMALLPOX: THE ORIGIN OF A DISEASE

The origin of smallpox as a natural disease is lost in prehistory. It is believed to have appeared around 10,000 BC , at the time of the first agricultural settlements in northeastern Africa (3, 4). It seems plausible that it spread from there to India by means of ancient Egyptian merchants. The earliest evidence of skin lesions resembling those of smallpox is found on faces of mummies from the time of the 18th and 20th Egyptian Dynasties (1570� BC ). The mummified head of the Egyptian pharaoh Ramses V (died 1156 BC ) bears evidence of the disease (5). At the same time, smallpox has been reported in ancient Asian cultures: smallpox was described as early as 1122 BC in China and is mentioned in ancient Sanskrit texts of India.

Smallpox was introduced to Europe sometime between the fifth and seventh centuries and was frequently epidemic during the Middle Ages. The disease greatly affected the development of Western civilization. The first stages of the decline of the Roman Empire ( AD 108) coincided with a large-scale epidemic: the plague of Antonine, which accounted for the deaths of almost 7 million people (6). The Arab expansion, the Crusades, and the discovery of the West Indies all contributed to the spread of the disease.

Unknown in the New World, smallpox was introduced by the Spanish and Portuguese conquistadors. The disease decimated the local population and was instrumental in the fall of the empires of the Aztecs and the Incas. Similarly, on the eastern coast of North America, the disease was introduced by the early settlers and led to a decline in the native population. The devastating effects of smallpox also gave rise to one of the first examples of biological warfare (1, 7). During the French-Indian War (1754�), Sir Jeffrey Amherst, the commander of the British forces in North America, suggested the deliberate use of smallpox to diminish the American Indian population hostile to the British. Another factor contributing to smallpox in the Americas was the slave trade because many slaves came from regions in Africa where smallpox was endemic.

Smallpox affected all levels of society. In the 18th century in Europe, 400,000 people died annually of smallpox, and one third of the survivors went blind (4). The symptoms of smallpox, or the “speckled monster” as it was known in 18th-century England, appeared suddenly and the sequelae were devastating. The case-fatality rate varied from 20% to 60% and left most survivors with disfiguring scars. The case-fatality rate in infants was even higher, approaching 80% in London and 98% in Berlin during the late 1800s.

The word variola was commonly used for smallpox and had been introduced by Bishop Marius of Avenches (near Lausanne, Switzerland) in AD 570. It is derived from the Latin word varius, meaning “stained,” or from varus, meaning “mark on the skin.” The term small pockes (pocke meaning sac) was first used in England at the end of the 15th century to distinguish the disease from syphilis, which was then known as the great pockes (8).


How Rinderpest was eradicated

Infected animals suffered from symptoms such as fever, wounds in the mouth, diarrhea, discharge from the nose and eyes, and eventually death. Death rates during rinderpest outbreaks were remarkably high, up to 100% in particularly susceptible herds. 2

While Rinderpest did not infect humans it severely affected their livelihoods. Rinderpest outbreaks caused famines responsible for millions of deaths. 3

The virus spread via droplets, so that animals got infected by inhaling sick animals’ breath, secretions or excretions. Rinderpest was a so-called dead-end disease for wild herds as their low population density inhibited the disease spread. Together with the development of a potent vaccine in 1960, the dead-end in wild herds played an important role in achieving the disease eradication in 2011. It is the first — and until today the only — animal disease to be eradicated. 4 5

The means by which rinderpest was eradicated

The fight against rinderpest was successul in driving down case numbers even before the invention of a potent vaccine in 1960. This illustrates that while having effective means against a disease was important for eradication, the proper implementation of other measures significantly reduced the disease burden even before.

Before the development of a vaccine, quarantine, improved hygiene, slaughter and inoculation were common practices in containing rinderpest. 6 The former two practices were effective thanks to rinderpest’s transmission requiring close contact between infected and susceptible animals. Europe managed to achieve rinderpest elimination this way at the beginning of the 20th century, long before the introduction of the vaccine. 7

Slaughter was another means to contain Rinderpest’s spread. It was understandably less popular because all cattle had to be killed if one infected member was identified. Nevertheless, European Russia successfully eliminated rinderpest largely this way in 1908.

Inoculating cows with inactivated virus samples from infected animals was an idea inspired by the variolation practice against smallpox in humans. Thailand, the Philippines and Iran, for example, managed to eliminate rinderpest before the Second World War largely using inactivated virus samples from cows. 8

In 1960 the English veterinary scientist Walter Plowright developed an inactivated vaccine – a tissue culture rinderpest vaccine, or TCRV – that induced lifelong immunity without major side effects or the risk of further transmission and which could be produced at a low cost. His success was based on figuring out how to grow the rinderpest virus in a laboratory outside of living organisms. 9 In 1961, Albert Sabin used the same method to develop an oral polio vaccine. 10 Plowright was awarded with the World Food Prize in 1999 for making rinderpest’s 𠇎radication, for the first time in human history, a practical objective”. 11

As the map shows, Rinderpest was only ever endemic in Europe, Asia and Africa – in addition to this there were two isolated outbreaks in Brazil in 1920 and Australia in 1923. 12

In 1994, the FAO launched the Global Rinderpest Eradication Programme (GREP) with the goal of eradication by 2010. 13 Thanks to the program’s global surveillance and vaccination efforts (a ring vaccination strategy similar to that applied to smallpox was used) 14 , the last known rinderpest outbreak occurred in Kenya in 2001 with the last case being recorded in Mauritania in 2003. Over the next ten years, the GREP continued to search for rinderpest samples. Finding none, rinderpest was declared eradicated by the World Organization for Animal Health (OIE) on 25 May 2011. 15

Unfortunately, no data on rinderpest cases and deaths seem to exist on a global level. 16

While Western Europe already eliminated Rinderpest successfully by the end of the 19th century, the last Asian case was recorded in Pakistan in 2000 and the last global case was documented in Kenya in 2003.

In 2014, 23 countries were reported to still hold samples of the rinderpest virus which is why the OIE and FAO aim to destroy most remaining rinderpest virus stocks and store a few remaining samples under international supervision in approved laboratories. 17

The eradication of rinderpest from 1945 to 2011 is estimated to have cost the equivalent of 2017-USD 5.5 billion 18 but to our knowledge there is no assessment of the economic benefits of the eradication. It is worth noting, though, that the 1982-1984 outbreak in most of Africa caused the loss of livestock of the equivalent value of at least 2017-USD 1.02 billion. 19

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Endnotes

The disease was also found in animals such as zebus, eland, kudu, wildebeest, antelopes, bushpigs, warthogs, giraffes, sheep, and goats. The Rinderpest virus is a member of the Morbillivirus family. FAO. (2015). Transmission of Rinderpest. FAO’s Animal Production and Health Division. Retrieved 16 February 2018, from http://www.fao.org/ag/againfo/programmes/en/rinderpest/dis-trans.html.

OIE – World Organisation for Animal Health. (2018). General Disease Information Sheets – Rinderpest. World Organization for Animal Health. Retrieved 8 February 2018, from http://www.oie.int/fileadmin/Home/eng/Media_Center/docs/pdf/Disease_cards/RINDERPEST-EN.pdf.

For example, when Rinderpest was introduced to Ethiopia in 1880, more than 90% of its cattle population died. Farmers depended on cattle for their meat consumption but also for plowing and fertilizing their fields. On top of that, the outbreak coincided with a drought, so Pankhurst (1968) estimates that one third of the Ethiopian human population died between 1888 and 1891.

OIE – World Organisation for Animal Health announcement. Retrieved 25 May 2011 from http://www.oie.int/for-the-media/press-releases/detail/article/no-more-deaths-from-rinderpest/.

Pankhurst, R. (1968). Economic History of Ethiopia, 1800-1935. Addis Abeba: Haile Selassie I University Press.

Inoculation refers to the practice of inserting viral matter of an infected animal into a healthy animal to effect a milder infection and subsequently immunity. This practice was a commonly practiced measure for smallpox protection before the invention of a potent vaccine.

Pg. 108 of Barrett, T., Pastoret, P., & Taylor, W. (2005). Rinderpest and peste des petits ruminants: Virus Plagues of Large and Small Ruminants. Amsterdam: Elsevier Science. Partially available on ebook central or google books.

A renewed outbreak in Belgium in 1920 inspired the founding of the World Organization for Animal Health (OIE, Office International des Epizooties) four years later in Paris on 25 January 1924, with 28 founding member countries.
OIE – World Organisation for Animal Health. About us: History. Retrieved 16 February 2018, from http://www.oie.int/about-us/history/.

More information can be found in Barrett, T., Pastoret, P., & Taylor, W. (2005). Rinderpest and peste des petits ruminants: Virus Plagues of Large and Small Ruminants. Amsterdam: Elsevier Science. Partially available on ebook central or google books.

Tissue culture attenuation: the virus was grown in cattle’s kidney cells, which can replicate in a laboratory. This method allows the controlled replication of virus over and over. The virus adapts to the cells over time, making it less dangerous to living cattle. From the 70th passage onwards, so the 70th time it was added to new cells, the virus was no longer harmful to cattle. The resulting virus would then be isolated from the kidney cells, dried for storage and used as for vaccination.

Mariner, J., House, J., Mebus, C., Sollod, A., Chibeu, D., & Jones, B. et al. (2012). Rinderpest Eradication: Appropriate Technology and Social Innovations. Science, 337(6100), 1309-1312. The abstract can be found online on the Science Magazine’s website.

The World Food Prize (2018) 1999: Plowright. Retrieved 7 July 2018, from https://www.worldfoodprize.org/en/laureates/19871999_laureates/1999_plowright/.

Hamilton, K., Visser, D., Evans, B., & Vallat, B. (2015). Identifying and Reducing Remaining Stocks of Rinderpest Virus. Emerging Infectious Diseases, 21(12), 2117-2121. Available online on the CDC website.

Food and Agriculture Organization of the United Nations. The Global Rinderpest Eradication Programme Progress report on rinderpest eradication: Success stories and actions leading to the June 2011 Global Declaration. Retrieved 16 February 2018, from http://www.fao.org/ag/againfo/resources/documents/AH/GREP_flyer.pdf.

Roeder, P., Mariner, J., & Kock, R. (2013). Rinderpest: the veterinary perspective on eradication. Philosophical Transactions Of The Royal Society B: Biological Sciences, 368(1623), 20120139-20120139. Freely available online here.

OIE – World Organisation for Animal Health. No more deaths from rinderpest. Retrieved 25 May 2011, from http://www.oie.int/for-the-media/press-releases/detail/article/no-more-deaths-from-rinderpest/.

This is partly because animal diseases were not as closely documented as human diseases but also because making rinderpest data available publicly could have endangered countries’ trade prospects in cattle and meat.
Pg. 105 of Barrett, T., Pastoret, P., & Taylor, W. (2005). Rinderpest and peste des petits ruminants: Virus Plagues of Large and Small Ruminants. Amsterdam: Elsevier Science. Partially available on ebook central or google books.

However, the World Organisation for Animal Health’s Youtube channel features a video of Rinderpest outbreaks from 376 until 2011.

Hamilton, K., Visser, D., Evans, B., & Vallat, B. (2015). Identifying and Reducing Remaining Stocks of Rinderpest Virus. Emerging Infectious Diseases, 21(12), 2117-2121. Available online on the CDC website.

Youde (2013) reports the cost to be $5 billion. Assuming that the estimate stems from 2011, the year of eradication, the conversion to 2017 US-$ was conducted using the GDP deflator on the website ‘measuring worth‘.

Youde, J. (2013). Cattle scourge no more: The eradication of rinderpest and its lessons for global health campaigns. Politics and the Life Sciences, 32(1), 43-57. Publicly available online here.

The FAO (197) reports the loss to be ‘at least $500 million’. We used the year 1984 as a base year and calculated the 2017 equivalent using the GDP deflator on the website ‘measuring worth‘.

FAO. (1997). East African rinderpest epidemic contained, but FAO urges countries on in the fight to eradicate the cattle plague from the world by 2010. Retrieved from FAO website.

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