In a recent editorial entitled Eradicating disease: an ambitious but energising goal, David Dickson offers an in-depth perspective on disease eradication, and he is correct in saying that eradication strategies, though important, will be challenging.
One key reason is that we do not yet fully understand disease patterns. And new or re-emerging diseases will only add more complexity that could stand in the way of eradication goals.
Health scientists point out that global warming may affect patterns of disease, and this could have a dramatic impact on public health strategies for disease prevention and control. The variable effects of climate change on different diseases will also complicate eradication programmes. Many microbial and vector-borne diseases will be sensitive to climatic changes, but some disease-causing organisms or vectors will be less responsive.  For example, initiating a campaign to eradicate a disease in a tropical region without knowing that it has already shifted to other areas will render control efforts ineffective.
Ecologists may have reservations about the idea of eradicating a disease, which stem from the belief that mechanisms already exist in nature to maintain ecological balance and the co-existence of living organisms. This suggests that eradicating one organism may change that balance, with negative impacts on the whole ecosystem. A news feature published in Nature last year highlighted both positive and negative aspects of eradicating mosquitoes, bringing to light the possible outcomes of permanently removing an organism from the world. 
It seems only right that before embarking on eradication programmes, public health authorities must consult epidemiologists and ecologists, seeking a broad scientific consensus. Brainstorming sessions should be conducted at different levels of government, inviting diverse views, involving schools and higher-learning institutions, and generating public awareness. A high-level meeting at a global level, where participants from different countries can debate disease eradication and formulate an agenda for future action, would also be useful.
But first, we need innovative research and systematic monitoring programmes to obtain first-hand information about patterns of disease occurrence.
 Slenning, B. D. Global climate change and implications for disease emergence. Vet Pathol 47, 28 doi: 10.1177/0300985809354465 (2010)
 Fang, J. Ecology: A world without mosquitoes. Nature 466, 432 doi: 10.1038/466432a (2010)