posts: 28085

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                        "text": "It is not possible to clearly draw a line between eradicable and non-eradicable diseases. New diseases can potentially be eradicated when scientific discoveries provide us with new tools to fight them.",
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                        "text": "Two conditions are absolutely necessary for a disease to be eradicable and there are several characteristics of diseases which make it more likely for a disease to be eradicable.",
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                "text": [
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                        "text": "Necessary conditions",
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                        "text": "It is an infectious disease",
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                        "text": "For a disease to be eradicable it needs to be a disease you can \"catch\", for example from other humans or animals, i.e. it has to be infectious. Non-infectious diseases, such as heart disease or cancer,\u00a0cannot be eradicated.{ref} There are also certain metabolic diseases that could be cured in all humans provided sufficient nutrition. These are mainly vitamin or essential element deficiencies such as scurvy (lack of vitamin C) or ion deficiency disorders. However, while it is theoretically possible that no human in the world would have one of these metabolic diseases at some point in time, these diseases will never be eradicated because they will return if a person's nutritional status changes. {/ref}",
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                "text": [
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                        "text": "We can prevent an infection or we have a way to treat it",
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                        "text": "To eradicate a disease we need to know of measures to fight its spread. The summary table above illustrates the diversity of such means against diseases.",
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                        "text": "Whilst the characteristics of a disease are biologically-determined or fixed, the available measures against the disease can progress through our scientific understanding and technological developments. This is where human ingenuity makes the fight against a disease possible. We discuss the different types of measures against infectious diseases next.",
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                "text": [
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                        "text": "Features which make eradication easier",
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                        "text": "There are five key characteristics which are not absolutely necessary but make eradication easier.\u00a0Dowdle (1999) writes:\u00a0",
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                                "text": "\u201cIn theory if the right tools were available, all infectious diseases would be eradicable. In reality there are distinct biological features of the organisms and technical factors of dealing with them that make their potential eradicability more or less likely.\u201d",
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                        "text": "{ref}Dowdle, W.R. (1999) The principles of disease elimination and eradication.\u00a0",
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                        "children": [
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                                "text": "Bulletin of the World Health Organization",
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                        "text": ". 1998;76(Suppl 2):22-25. Online ",
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                        "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2305684/",
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                                "text": "here",
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                        "text": ".{/ref}",
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                "text": [
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                        "text": "The disease is caused by only a small number of pathogens",
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                        "text": "Infectious diseases are caused by pathogens. These disease-causing microorganisms include bacteria, viruses, unicellular parasites, or larger parasites such as worms. We included them for all diseases discussed here in our summary table at the beginning of this entry. To eradicate a disease its pathogen needs to be eradicated. This means that diseases caused by one or a small number of pathogens are easier to eradicate than the ones caused by a larger number of pathogens. Examples make this clear:",
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                                "text": "Smallpox, for instance, is caused by only two types\u00a0of viruses that were eradicated in 1977 using a vaccine.",
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                                "text": "Lung infections, on the other hand, are an example of a disease named after their shared symptom: infection of the lung. But these symptoms can be caused by a large number of viruses and bacteria. This makes the disease \"lung infection\" non-eradicable.\u00a0Wound infections are an even more extreme example as they can be caused by many bacteria that would not be harmful to a healthy human with intact skin.",
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                        "text": "In other words, disease-causing organisms can be eradicated but not necessarily symptoms.",
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                "text": [
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                        "text": "The disease has only a single host",
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                        "text": "Diseases that only infect one species are easier to eradicate than diseases that infect many species, i.e. that have \"alternative hosts\". Smallpox, for instance, was caused by a virus that only survived in and spread among humans.",
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                        "text": "Other diseases that have only humans as a host are:",
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                                "text": "polio,",
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                                "text": "Guinea worm disease (dracunculiasis),",
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                                "text": "measles,",
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                                "text": "mumps,",
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                                "text": "pertussis (whooping cough), and",
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                                "text": "diphtheria.",
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                        "text": "Many diseases unfortunately either rely on several hosts (vector-transmitted) or can even have several hosts as alternative reservoirs:",
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                        "text": "Malaria, lymphatic filariasis, and river blindness are examples of\u00a0",
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                                "text": "vector transmitted",
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                        "text": "\u00a0diseases. This means that the pathogen\u00a0",
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                        "children": [
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                                "text": "requires several\u00a0hosts",
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                        "text": " in its life cycle. The malaria parasite, for instance, needs both humans and certain types of mosquitos to survive.\u00a0In a hypothetical scenario of all humans being cleared of malaria at the same time, mosquitoes could still carry the disease and re-infect humans. However, if all humans could somehow be protected from infections for a few months at the same time, the malaria parasite would eventually die out as all malaria-carrying mosquitos naturally have a short life span. If the malaria parasite was therefore not able to live on in humans before the malaria-carrying mosquitoes die a natural death, the parasite would be eradicated.",
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                        "text": "The influenza virus (which causes influenza or \"the flu\"), is an example of a pathogen ",
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                                "text": "with several alternative hosts",
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                        "text": ". The influenza virus can infect humans, birds, pigs and other animals. It\u00a0could survive in these animals even if all humans were somehow made immune. This means that even if a vaccine against all strains of the influenza virus existed,\u00a0one would still have to immunize all humans, pigs and even wild birds to eradicate influenza.",
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                        "text": "Other examples of diseases with alternative hosts are",
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                                "text": "rinderpest (infected cattle, buffalo, zebras, water buffaloes,\u00a0African buffaloes, elephants, kudu, wildebeest,\u00a0various antelopes, bushpigs, warthogs, giraffes,\u00a0sheep, and goats);",
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                                "text": "hepatitis A (which infects humans and other vertebrates);",
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                                "text": "ebola (infects bats as well as some bigger mammals);",
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                                "text": "rabies (infects all warm-blooded vertebrae including all mammals); and",
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                                "text": "Japanese encephalitis (a so-called ",
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                                        "text": "dead-end disease",
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                                "text": "\u00a0in humans, sheep, and cattle, which means that it is fatal and cannot spread, and is only transmitted among pigs).",
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                        "text": "While it makes eradication easier when there is only one host, we know it is not a requirement: Rinderpest was successfully eradicated in 2011 and it was a disease with alternative hosts that affected cattle, sheep and goats but also antelopes, buffaloes, deers, giraffs, wildebeests and warthogs. However, most cases occurred in domesticated animals so that eradication was achieved by vaccinating all domestic species in parallel.",
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                        "text": "Diseases that are vector transmitted will be easier to eradicate than those with alternative hosts, because one has to eradicate the pathogen from only one species for a sufficiently long time.",
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                        "text": "The fact that the pathogen is reliant on several hosts makes vector transmitted diseases easier to eradicate than diseases with several alternative hosts but harder to eradicate than diseases with just one host. In reality, more factors play a role in determining whether a disease is eradicable or not. Malaria, for instance, is a vector-transmitted disease but it is not currently eradicable because no good measures exist against it.",
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                "text": [
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                        "text": "The disease is visible and good diagnostics exist",
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                        "text": "Good monitoring of outbreaks is essential for eradicating a disease as it allows us to contain an outbreak and prevent the spread of the disease.",
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                        "text": "If the disease has visible symptoms in the majority of infections or when a good diagnostic method exists, monitoring is easier. A smallpox infection, for instance, always led to visible pox and made monitoring simple.\u00a0Pictures of infected people were shown and allowed health workers to find cases even in remote villages.{ref}In addition to easily documenting cases, its high visibility also allowed for the application of the\u00a0ring-vaccination principle. Instead of having to run mass immunization campaigns which are expensive and logistically challenging, health workers only vaccinated people that might\u00a0come in contact with a smallpox-infected person.{/ref}",
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                        "text": "Less visible diseases are harder to monitor. If symptoms only show in a minority of infections (e.g. polio) or if a diagnosis is difficult the disease can more easily spread unnoticed.",
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                        "text": "Another aspect that makes monitoring harder is if a disease is stigmatized. Sexually transmitted diseases for example might be hidden from the community intentionally.",
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                        "text": "Elimination has proven possible",
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                        "text": "It is promising if a disease has already been eliminated from certain geographical areas such as islands or even whole world regions.{ref}Hopkins, D. (2013). Disease Eradication. ",
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                                "text": "New England Journal Of Medicine,",
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                        "text": " 368(1), 54-63. Available online ",
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                        "url": "http://www.nejm.org/doi/full/10.1056/nejmra1200391",
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                                "text": "here",
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                        "text": ".{/ref}",
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                        "text": " If, on the other hand, no country has ever eliminated a disease, it is likely that the current means against a disease are not effective enough yet to make eradication possible.{ref}",
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                        "text": "This is unfortunately the case for HIV and Tuberculosis.",
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                        "text": "\nThere are five countries that managed to eliminate malaria between 1987 and 2007 (Armenia, Maldives, Morocco, Turkmenistan and the United Arab Emirates). However, neighboring countries of these still have malaria. While this is great news, malaria is not yet eradicable. Pathogens do not respect boarders, therefore the time malaria will be considered eradicable will be once a whole geographic region has eliminated the disease.",
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                        "text": "\nFor more information on this see: World Health Organisation (2018) ",
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                        "children": [
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                                "text": "Overview of malaria elimination",
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                    {
                        "text": ". Last updated 13 March 2018. Available online ",
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                        "url": "http://www.who.int/malaria/areas/elimination/overview/en/",
                        "children": [
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                                "text": "here",
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                        "text": ". Enlarge the blue-red image to access the country names.{/ref}",
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                        "text": "Once a geographic region or indeed most countries worldwide have eliminated a disease, eradication becomes a feasible target.\u00a0Currently there are three diseases that fall in this category: Polio, Guinea worm disease, and yaws.",
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                        "text": "The perceived disease burden is high and financial, political and community support are available",
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                        "text": "The perceived burden of a disease, the estimated cost of eradication, and the political stability of affected countries are further factors that determine the eradicability of diseases.",
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                        "text": "Polio is a good example here as it illustrates the powerful impact of both a unified international effort and local political support. In 1988, the ",
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                                "text": "Global Polio Eradication Initiative",
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                        "text": " was set-up which has provided large-scale and, importantly, continued support for the eradication of polio. The number of paralytic polio cases has been greatly reduced such that in 2018 it is considered endemic in only three countries: Pakistan, Afghanistan, and Nigeria.",
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                        "text": "But polio also illustrates that positive developments might reverse. Nigeria\u2019s case numbers, for instance, surged from 202 in 2002 to 1143 in 2006 because of suspicions that immunization campaigns were a cover for Muslim sterilization by the US government which lead to an 11-month {ref}Larson, H., & Ghinai, I. (2011). Lessons from polio eradication. ",
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                        "children": [
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                                "text": "Nature, 473",
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                        "text": "(7348), 446-447. Freely available online ",
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                        "url": "http://www.globe-network.org/sites/default/files/documents/public/en/news-and-events/news/2011/lessons-from-polio-eradication.pdf",
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                                "text": "here",
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                        "text": ".{/ref}boycott. The example of polio hence illustrates the importance of both international as well as local community support for eradication.",
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                        "text": " However, only Chad and Ethiopia recorded a positive number of Guinea worm cases in 2017.",
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                        "text": "The line chart illustrates the dramatic decline in the number of reported Guinea worm cases from two different data sources. From more than 892,000 reported cases in 1989, the number of reported Guinea worm infections dropped to only 13 infections worldwide in 2022 \u2013 6 in Chad, 5 in South Sudan, 1 in Central African Republic and 1 in Ethiopia.",
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                        "text": "For the early period especially the number of reported cases is much lower than the true number of cases. Greenaway (2004) reports an estimate of 3.5 million cases for the year 1986.{ref}Chris Greenaway (2004) \u2013 Dracunculiasis (guinea worm disease). Canadian Medical Association Journal. 170 (4): 495\u2013500.{/ref}",
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                "url": "https://ourworldindata.org/grapher/number-of-reported-guinea-worm-dracunculiasis-cases?tab=chart&country=OWID_WRL~ETH~TCD~SSD~CAF",
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        "type": "article",
        "title": "What makes disease eradicable - old version",
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        "dateline": "November 19, 2019",
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    "createdAt": "2019-11-19T13:02:21.000Z",
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    "updatedAt": "2023-06-30T13:32:29.000Z",
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    "publishedAt": "2019-11-19T13:02:07.000Z",
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