Written by Sarah Wondmeneh, MD/MPH Candidate at Washington University in St. Louis
In the late 1980s, the World Health Organization (WHO) declared commitments to globally eradicate dracunculiasis (guinea worm) and poliomyelitis. [1]
The International Task Force for Disease Eradication has recommended additional diseases with eradication potential, including lymphatic filariasis, measles, mumps, rubella and cysticercosis. Although the prevalence and incidence of many of these diseases have dramatically decreased (ex. Figure 1), none have been eradicated. While all disease control programs face specific challenges related to the pathogen and available tools, disease eradication programs encounter a set of shared barriers that emerge during the endgame or “last mile.”
To explore these challenges, we first need to clarify exactly what the term eradication means. With eradication, transmission of a specific pathogen is permanently interrupted, worldwide.2 There is no risk of re-establishment of the infection, and control efforts can be discontinued. The societal and financial benefits of eradication are substantial. After smallpox was eradicated, vaccination or quarantine efforts were discontinued; besides saving millions of people from death and disability, more than US$1 billion was saved annually.3 Eradication is often confused with elimination – the lack of transmission in a specific geographical location.2 Essentially, to have global eradication, you must first achieve elimination in countries and regions. With elimination, control measures have to continue in case the pathogen is reintroduced from other areas.1
Unfortunately, not every infectious disease agent can be eliminated or eradicated. Important characteristics must be present. Is it scientifically feasible with existing knowledge and tools? Is there adequate public health infrastructure and funding? Will there be sustained political and societal buy-in?2 In some cases elimination can occur even without WHO formally articulating this as a goal. More than 85% of affected countries had eliminated smallpox by the time the initiative was formalized in 1967.2 However, WHO leadership and declarations can be important for helping remaining endemic regions join eradication programs by coordinating commitment and resources from the global community.
Even with global commitment, several challenges arise in the last stretch of driving transmission in an area to zero. The remaining foci of infection are inevitably those that are the hardest to reach, whether in remote or migratory communities or in areas of sparse health services.4 Infections may also largely present without any signs or symptoms, making passive surveillance inadequate.5 People can lose immunity, or organisms may become resistant to anti-microbial agents. Therefore, ongoing research is essential to improve tools and strategies and to modify surveillance and communication methods.
Socio-political commitment at the local and national levels is just as important as biologic and technical feasibility.
Individuals may not perceive control measures as necessary or beneficial to them or their families. A classic example is vaccination compliance – it has been demonstrated that vaccine refusal increases as disease incidence falls.6 Communities can become disengaged with eradication efforts because they no longer perceive the threat to their health, and this increases the risk of resurgence of the infection. Cultural traditions, religious beliefs, and civil strife can also hamper progress.2 The human element is a key component in all disease control, elimination, and eradication initiatives.
There are also financial challenges associated with disease elimination and eradication programs. The unit cost per case prevented rises steeply when infection rates decrease;5 a prolonged endgame may lead to donor fatigue, program fatigue, and an increased risk of re-emergence as interventions are scaled down. Behavioral and social research is vital to understand barriers and priorities of local communities so that evidence-based communication strategies can increase adherence with interventions.
Though top-down global coordination is essential, disease elimination and eradication programs are comprised of many local programs and activities. If it takes a village to raise a child, it takes thousands of villages, cities, governments, laboratory and social scientists, and donors, committed and working together, to traverse the last mile required for disease eradication.
References
- Hopkins, D. R. (2013). Disease Eradication. New England Journal of Medicine, 368, 54-63. doi:10.1056/NEJMral200391
- Dowdle, W. R., & Cochi, S. L. (2011). The principles and feasibility of disease eradication. Vaccine, 29S, D70-D73. doi: 10.1016/j.vaccine.2011.04.006.
- (2010) Statue commemorates smallpox eradication. Retrieved from http://www.who.int/mediacentre/news/notes/2010/smallpox_20100517/en/
- Molyneux, D. H. (2015). Eradication and elimination: facing the challenges, tempering expectations. Int Health, 7, 299-301. doi:10.1093/inthealth/ihv050
- Klepac, P., Funk, S., Hollingsworth, T., Metcalf, C. E., & Hampson, K. (2015). Six challenges in the eradication of infectious diseases. Epidemics, 10, 97-101. doi: 10.1016/j.epidem.2014.12.001.
- Saint-Victor, D. S., & Omer, S.B. (2013). Vaccine refusal and the endgame: walking the last mile first. Philos Trans R Soc Lond B Biol Sci, 368, 20120148. doi:10.1098/rstb.2012.0148
- Wilson, J. (2014). The ethics of disease eradication. Vaccine, 32, 7179-7183. doi:10.1016/j.vaccine.2014.10.009
[1] Some also aim for elimination “as a public health problem” (ex. lymphatic filariasis). The requirements for an infectious disease to no longer be a public health problem is subjective, usually based on expert opinion. This terminology can also lead to a false perception that a disease no longer exists or is limited though many cases could remain.