|DR A. L. SAHA MEMORIAL ORATION
|Year : 2011 | Volume
| Issue : 2 | Page : 81-87
Eradicating and eliminating infectious diseases: Past, Present and Future
Jai P Narain
Director, Sustainable Development and Healthy Environments, World Health Organization, New Delhi, India
|Date of Web Publication||22-Sep-2011|
Jai P Narain
Director, Sustainable Development and Healthy Environments. World Health Organization, I.P. Estate, New Delhi - 110 002
Source of Support: None, Conflict of Interest: None
| Abstract|| |
During the past 60 years, a number of infectious diseases have been targeted for eradication or elimination, with mixed results. While smallpox is the only one successfully eradicated so far, campaigns on yaws and malaria brought about a dramatic reduction in the incidence in the beginning of the campaign but ultimately could not achieve the desired goal. There is again a renewed interest in disease eradication. The World Health assembly in May 2010 passed a resolution calling for eradication of measles by 2015; the target of polio eradication still remains elusive. In view of these developments, it is appropriate time to revisit the concept of disease eradication and elimination, the achievements and failures of past eradication programmes and reasons thereof, and possibly apply these lessons while planning for the future activities. This paper based on the Dr. A.L.Saha Memorial Oration describes various infectious diseases that have been targeted for eradication or elimination since 1950s, the potential direct and indirect benefits from disease eradication, and the issues and opportunities for the future.
Keywords: Infectious diseases, Eradication, Elimination, Smallpox, Achievements, Lessons learnt
|How to cite this article:|
Narain JP. Eradicating and eliminating infectious diseases: Past, Present and Future. Indian J Public Health 2011;55:81-7
|How to cite this URL:|
Narain JP. Eradicating and eliminating infectious diseases: Past, Present and Future. Indian J Public Health [serial online] 2011 [cited 2017 Sep 25];55:81-7. Available from: http://www.ijph.in/text.asp?2011/55/2/81/85236
| Introduction|| |
A renewed interest and fascination for disease eradication was generated in May 1980, when the World Health Assembly representing all the then 155 Member States of the World Health Organization (WHO) unanimously declared that the world was free from smallpox - the first and only time a disease has been successfully eradicated from this planet. This ultimate public health achievement was clearly a result of high level commitment, inter-country collaboration, and the efforts of dedicated and committed individuals across political and ideological boundaries in a campaign that began in late 1950s and lasted nearly 20 years. This the greatest and the most singular triumph in human history led to a renewed interest in disease eradication and elimination and many campaigns have since been launched, with mixed results. Most recently, in May 2010, the World Health assembly passed a resolution calling for eradication of measles by 2015.  Also, the world is now in the final stages of polio eradication; India is a focus of attention along with three other countries where polio remains endemic. However, there is a healthy debate going on among the scientific community as to whether we should be investing significant resources on one disease while there are many other health problems to combat, and especially when the financial resources are limited.
It is timely therefore to review the concept of disease eradication, take stock of the achievements made and the lessons learnt over past five decades and use these lessons in the 21 st century. This paper based on the Dr. A.L. Saha Memorial Oration describes the rationale of disease eradication, past eradication efforts and the progress in current disease eradication efforts and the way forward.
| Definition of and rationale for disease eradication and elimination|| |
A generally accepted definition of eradication is permanent reduction to zero of the worldwide prevalence of a disease caused by a specific agent, thereby creating an environment where intervention measures are no longer needed. , The elimination, on the other hand, is defined as reduction to zero of prevalence of a disease in a defined area due to deliberate efforts. But contrary to eradication, intervention measures are still required since the disease is persisting elsewhere. Elimination is also defined in terms of public health problem as a reduction of prevalence to such a low level that it is no longer considered a public health problem, based on an arbitrary criteria or definition.
Given the ambiguities associated with these definitions, efforts are presently underway to revisit these definitions. , Considerable experiences have been gained so far which could be used to ascertain what criteria can be used to assess diseases that have the potential for and can be targeted for eradication or elimination.Eradicating a disease is attractive conceptually because such an effort can dramatically reduce or eliminate the burden of disease and associated deaths. Besides saving significant amounts of money and in particular obviating the need for further investments, eradication programmes also address specific public health, economic and humanitarian needs. In addition, they can bring about major benefits across a broad spectrum of public health by strengthening disease surveillance, laboratory capacity and health care delivery system.  However, eradication of an infectious disease would be considered possible only if it meets a certain criteria including those relating to the disease epidemiology and availability of the right tools. But more importantly, social and political factors play an equally critical role in ultimately determining whether an eradication programme will be successful or not.
During the past 60 years, a number of infectious diseases have been targeted for eradication. These include the yaws eradication goal declared by WHO in 1954, followed by a similar goal of malaria eradication announced in 1955, smallpox eradication in 1958, guineaworm in 1986, polio eradication in 1988, and, in May 2010 the sixty-third World Health Assembly declared the goal of measles eradication to be achieved by 2015. However, the progress report of eradication programmes over the years is rather mixed. While smallpox is the only one successfully eradicated, campaigns on yaws and malaria brought about a dramatic reduction in the incidence in the beginning of the campaign but ultimately could not achieve the desired goal.
| Looking back in history: The report card of eradication programmes|| |
Eradication programmes that were successful: Smallpox
The story of smallpox eradication began in 1796 when Edward Jenner undertook his famous experiments which led to the development of smallpox vaccine. He inoculated a boy with pus from a cowpox lesion and then again after two months successfully inoculated him with smallpox virus as the child did not develop the disease, indicating that infection with cowpox protected against smallpox. This led the way to the development of smallpox vaccine which was used throughout the 19 th and early 20 th centuries as mass vaccination in the industrialized countries. But many developing countries had no access to vaccine and suffered from the devastating impact of smallpox.
In 1967, smallpox was endemic in as many as 31 countries, a life threatening disease with very high case fatality rate of 20% to 40% causing over 2.7 million deaths. In addition, millions went blind and all those affected had permanent facial scarring [Figure 1].
The process of worldwide eradication of smallpox was set in motion and the global campaign to eradicate smallpox began in 1967 led by WHO. The eradication programme was based on a new evidence-based strategy developed by Dr Bill Foege of the US Centers of Disease Control (CDC) while working in Nigeria.  It consisted of search for smallpox cases and containment by vaccination of households around the case also called ring vaccination. This was an excellent example of the use of an epidemiological approach in strategy development. The intensive search was conducted by using a recognition card in house-to-house searches, in marketplaces and bazaars seeking out smallpox cases using recognition card. Towards the latter part of the campaign, a reward was announced for those who would report the suspected cases. The smallpox eradication programme benefited greatly from a vaccine that was thermo-stable and was administered through a bifurcated needle by making punctures in the skin which provided long-lasting immunity.
Ten years after the world-wide campaign was launched, the last case was reported in 1977 in Somalia. In 1980, the WHO Certification Committee confirmed eradication of smallpox by issuing certificate of eradication signed by 20 global experts and in May 1980, the World Health Assembly announced that the world was free from smallpox.
Eradication programmes that did not succeed: Malaria, yaws and yellow fever
The eradication programmes that did not succeed include malaria, yaws eradication during 1950s and yellow fever. Yellow fever has never been reported in India, hence not covered in this paper. At the height of the malaria situation in 1953, when close to 75 million people were estimated with malaria in India alone, the malaria eradication programme was launched which had a dramatic impact, as the numbers decreased remarkably to two million in 1958 and then to only 50,000 in 1961. 
Unfortunately, however, malaria started to increase from 1970 onwards peaking with six million cases in 1975 [Figure 2]. The malaria eradication programme was historically the single biggest public health programme in India at that time. Despite remarkable progress initially in India and many other countries, the programme unfortunately received a setback later on and failed to achieve the desired goal of eradication. The reasons for failure were primarily of a technical nature; the programme depended solely on one tool, i.e., DDT spraying and when resistance started to develop, this tool became useless.  There were, however, a few operational difficulties as well such as inadequate access to remote and politically unstable areas, infrastructural weakness as well as difficulty of maintaining technical standards in complex field operations. Besides, complacency was also a contributing factor.
Another disease that was targeted for eradication was yaws during the 1950s and 1960s. Yaws, a non-venereal treponematosis affecting skin in the early stages and bones in the late stages is present primarily among poor populations affecting mainly children below 15 years of age [Figure 3].
It was clear that active case finding and treatment of cases and contacts with a single injection of long-acting penicillin could eliminate the disease. Dramatic results were obtained during the 1950s leading to 95% reduction in the caseload between 1952 and 1964. , The programme, however, could not achieve eradication as the yaws surveillance and control activities were prematurely integrated into primary health care. In addition and in due course of time, the funding also became a limiting factor. Yaws soon became a forgotten disease; found today in isolated pockets in remote areas such as in Asia and Africa.
In 1996, using the same strategy of active case finding and treatment of cases and close contacts, the Government of India relaunched the yaws eradication programme and within a few years the disease was eliminated. Since 2004 not a single case has been reported in the country [Figure 4]. 
Encouraged by India's success, Indonesia and Timor-Leste are presently implementing yaws eradication programmes and a global campaign has also been launched.
Eradication programmes which are presently ongoing: Polio, guineaworm and yaws
Since the 1988 World Health Assembly resolution to eradicate poliomyelitis, considerable progress has been made towards interrupting the transmission of wild poliovirus globally. The number of polio cases has decreased from 350,000 reported from 125 countries in 1988, to only 110 cases in 2010 - in four endemic countries namely Afghanistan, India, Nigeria and Pakistan [Figure 5].
In India, there has been good progress since 2005 when nearly 66 cases were reported. There was a set back in 2006 but now things are back on track. As of September 2010 only 36 polio cases have been reported as compared to 312 cases for the same period in 2009. The experience of polio highlights the importance of host factors, as well as of the social and cultural determinants, the need to create demand for services and to reach the most unreached and underserved areas.
Guineaworm is another disease to be eradicated worldwide. However, India was certified as disease-free in February 2000. Guineaworm remains endemic in six African countries. 
Elimination programmes presently underway
In addition to diseases that have been targeted for eradication there are a number of diseases that have been considered for elimination rather than eradication. These include leprosy, lymphatic filariasis, and visceral leishmaniasis (kala-azar). 
While the South-East Asia Region carries the highest global burden of leprosy cases (nearly 3/4 th of all cases occur in this Region), overall the progress has been excellent. As of September 2010, 10 out of 11 Member States have achieved the elimination target (prevalence below one per 10,000 populations). Only Timor-Leste is yet to achieve the target which is expected within this year.
Lymphatic filariasis is also targeted for elimination by 2020. Progress in elimination of this disease which causes gross disfiguring, enlargement of legs, arms and genitalia has been quite remarkable. Of a total of 2500 million people covered globally with mass drug administration (MDA) till 2008, 86% were from this Region. [Figure 6]. In addition, three countries namely, Maldives, Sri Lanka and Thailand have already achieved the elimination target of less than 1% micro-filaria rate. In India too the progress is excellent. The 2010 data show that of the 220 endemic districts, 176 or 76% have achieved a micro-filaria rate of less than 1% or have achieved the elimination target.
Finally, kala-azar which is endemic in only three countries namely Bangladesh, India and Nepal. Kala-azar is a serious life threatening neglected tropical disease affecting the poorest of poor and those living in remote border areas. However, the disease is uniquely amenable to elimination in the South-East Asia Region because of the unique epidemiology, no animal reservoir, availability of new technology such as new rapid test (rk39) and effective treatment with miltefosine and high level of political commitment.  In 2005 the Health Ministers of these three endemic countries signed a Memorandum of Understanding in the sidelines of the World Health Assembly, in order to collaborate in kala-azar elimination. This is especially important because kala-azar is reported primarily from the border districts of the three countries.
| The future of disease eradication and elimination: Issues and opportunities|| |
What lessons can be learnt from smallpox eradication or which other eradication or elimination programmes can be applied to other programmes? Some key lessons include the need to understand the epidemiology and transmission of the disease before targeting it for eradication; the presence of effective tools for diagnosis, treatment and prevention; knowledge of the social, cultural and political factors which may vary from area to area; and the availability of a clear and well thought out strategy. ,, According to Dr Bill Foege " Smallpox eradication did not happen by chance, but it was due to a well conceived plan and implemented by a committed set of public health individuals".  This applies to other diseases as well. The eradication strategy should be based on a good surveillance system and on scientific information and evidence. "Moreover, the strategy that helped eradicate smallpox was based on science but the tactics used were based on local culture". Dr. Foege underlined that the successful missions are possible as a result of coalition and team work built on the foundation of mutual trust. The command and control aspects are also critical; in the case of smallpox, health professionals from multiple countries worked under the overall leadership and coordination of the national ministries of health.
In addition, the biological factors, availability of effective tools and means of their delivery can have an important bearing on the outcome. Smallpox eradication was possible because of the single serotype of the virus which was genetically stable, man was the only reservoir, diagnosis did not require complex laboratory investigations and the vaccine besides being thermostable, was very efficacious. While the tool in the form of an effective vaccine or treatment could be available, there is a need for continuously and systematically improving the tools and the techniques to deliver them. On the other hand, malaria eradication failed because the strategy depended entirely on DDT spray and with development of resistance to insecticides and also to drugs, there were no alternative effective tools available.
Looking into the future, what issues and challenges deem consideration?
First of all, there is considerable degree of confusion relating to the definition of eradication, elimination and elimination as a public health problem. A simple definition that could be proposed includes defining eradication as the absence of disease worldwide as a result of deliberate efforts and elimination defined as reduction to zero of a specific disease in a defined geographic area as a result of deliberate efforts. Such a straightforward definition would help advance the cause of disease eradication or elimination.
Secondly, before embarking on an eradication programme, there should be an agreement on a set of principles that would guide the strategy and action. These include 1) good understanding of the natural history of disease, 2) use of health information or evidence for strategy development; and 3) acknowledging that eradication efforts should not be at the expense of the ongoing programmes such as routine immunization in the case of polio eradication. Considerable attention must be given to planning, setting clear goals and ensuring overall coordination of efforts. Also, care should be taken to make sure that efforts towards disease eradication can supplement and complement the existing health system.
Thirdly, we should be careful not to declare success prematurely as was done in the case of yaws and malaria before the job was done. The last mile is always the hardest and the costliest as we can see in the case of the polio eradication programme. This is a challenge which must be thought through right from the planning stage.
Fourthly, diseases that are targeted for eradication or elimination should be selected based on a defined and pre-selected criteria which could include disease epidemiology, the natural history and reservoir of infection, availability of an effective intervention tool (biological feasibility), and ability to scale up interventions within a set time frame (operational and technical feasibility). These two criteria should be complemented by a critical analysis of factors such as political commitment, community engagement and trust, availability of funds, and effective communication strategies (economic and political feasibility). For advocacy and resource mobilization, it would be critical to make a strong economic argument based on the epidemiology and cost-benefit analysis. Achieving eradication or elimination of a disease, if it affects the poorest and most vulnerable populations of the society is also a social and ethical imperative.
Also, in the present environment of financial constraints, it is critical also to look at a problem on the basis of making an investment case. For example, the estimated cost of smallpox as a health problem was US$ 1350 million annually while the cost of the eradication programme was only US$ 23 million. It is estimated that if we could eradicate polio the annual savings globally would amount to US$ 1.5 billion. These data amply justify eradication as an investment case and therefore such data can be a powerful tool in convincing those who control the purse strings both at national and international levels. Besides disease-specific benefits from disease eradication or elimination, such programmes can provide collateral benefits- in terms of strengthening health systems in the form of virology laboratories that can support other disease control programmes or to other eradication programmes such as polio and measles using the same resources.
Finally, given the above arguments, one may ask whether there are any other infections or diseases that could be considered for elimination. A case can be made for elimination of perinatal transmission of Human Immunodeficiency Virus or HIV as a feasible goal, as also the elimination of congenital syphilis, trachoma and human rabies. These are all candidates for elimination, with the possible exception of trachoma which could qualify for eradication.
| Conclusion|| |
Substantial public health and economic benefits make disease eradication a compelling case; while effort is time limited, the benefits of eradication are eternal. However, a careful analysis is needed before embarking on disease eradication. Eradication of some diseases may be possible but it is not easy. For this a good understanding of disease epidemiology, availability of cost effective tools that can be taken to scale, and a broad coalition and partnerships both at the political and community levels are needed which can contribute towards a successful outcome. Most importantly, public health professionals in general and public health workers in particular will have to take a leadership role in making eradication possible. In today's world, the infectious disease agents are dynamic, resilient and capable of spreading across borders efficiently. Eradicating infectious diseases in the midst of globalization and rapid population movements add another important but challenging dimension to the problem. However, the shared and sustained commitment, political will and dedication of public health personnel can help in achieving the goal.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]