The cost of disease eradication. Smallpox and bovine tuberculosis.

Although eradication is the ideal approach to reduce the economic and human health costs of disease, there may be both short- and long-term consequences. A $300 million effort succeeded in completely eradicating smallpox in less than ten years. The campaign was effective because variola virus produced acute illness, had no carrier stage or non-human reservoirs, and had an effective vaccine that was used in combination with international surveillance and public education. Bovine tuberculosis was completely eradicated in many U.S. herds at a cost of $450 million over 50 years using a "test and slaughter" program combined with meat inspection. Mycobacterium bovis often does not produce acute disease, persists in the carrier stage, has multiple non-human reservoirs, and easily crosses species. No effective vaccine or centralized global surveillance or eradication programs currently exist. Control measures result in significant economic losses. Smallpox eradication had limited economic consequences but has left much of world's population highly susceptible to zoonotic orthopoxviruses and to the use of smallpox as a biologic weapon. The primary threat of M. bovis exists in wildlife that share watering holes or pasture land with domestic stock. In the developed world, surveillance can minimize risks, but one-third of the world's population lacks effective agricultural and food safety programs, leaving them at substantial risk for zoonotic infection by M. bovis.