The situation facing public health authorities who are responsible for the polio eradication effort is very complex and much effort has gone into developing current plans. The two-day workshop held by this committee was not designed to evaluate those plans and the description that follows should not be construed either as endorsement or criticism. Instead, this section is provided to acquaint the reader with the assumptions that the committee used in coming to its recommendations regarding the development of antiviral drugs against polio.
The successful campaign to eradicate smallpox stands as one of history’s greatest public health achievements. It has served as an inspiration for the huge commitment needed to eradicate other infectious diseases. Lessons learned from the smallpox campaign have informed the choice of diseases to target and the strategy behind later eradication campaigns. In 1988, the WHO identified poliomyelitis as a disease that merited global eradication and met the basic biological conditions for potentially successful eradication (Fenner et al. 1988):
The microbial agent infects only humans.
Humans are the only reservoir for the microbial agent.
The infection induces life-long immunity.
There is a tool or intervention that effectively interrupts the chain of transmission of the infectious agent from one individual to another.
OPV has been highly successful in interrupting the transmission of wild poliovirus through most of the eradication campaign; but as the final stages approach, the final condition is proving problematic. OPV, which contains live, attenuated versions of all three poliovirus types, does induce enduring immunity, but can itself transmit polioviruses to nonimmune people and, rarely, (1-2 per million recipients) causes paralytic disease. As long as OPV is used, new chains of transmission can be initiated among susceptible people. Interruption of these final challenging chains of transmission may require a different approach.
When the global polio eradication campaign was launched in 1988, poliovirus caused more than 350,000 cases of paralytic disease annually in more than 125 countries. By 2003, only 784 cases of poliomyelitis were reported in a total of 6 countries (Aylward et al. 2005). The tremendous success of this program occurred in spite of the fact that polio has proven in