The biologic principles of poliovirus eradication.

The biologic principles for the global eradication of poliomyelitis are as follows: Poliovirus causes acute, nonpersistent infections, virus is transmitted by infectious humans or their waste, survival of virus in the environment is finite, humans are the only reservoir, and immunization with polio vaccine interrupts virus transmission. These principles appear to be sound. The potential for prolonged virus excretion by immunocompromised patients requires further definition, although there is no epidemiologic evidence of a threat to eradication. Survival of poliovirus in the environment is highly variable, but viral inactivation is usually complete within months. Higher primates may be infected with poliovirus, but they are unlikely reservoirs in nature. The only poliovirus reservoir remaining after eradication will be laboratory stocks. Serious attention must be given to reducing this potential source of infection. Polio eradication through immunization is evidenced by the documented absence of poliomyelitis in an increasing number of countries and the progressive disappearance of poliovirus genotypes.