In coordination with the World Health Organization’s (WHO) announcement that that type-2 poliovirus has been eradicated globally, the Centers for Disease Control (CDC) have coordinated in synchronization with global regulations to destroy completely the remaining OPV2. In the future, poliovirus monitoring and early warning will be conducted through acute flaccid paralysis surveillance systems and environmental polio monitoring operations. 
The CDC indicates that since Taiwan isolated its last case of wild type-2 poliovirus in 1979, no traces of poliovirus have been found. The last case of polio caused by wild type-2 poliovirus in the world was found in India in 1999. Currently, wild type-1 poliovirus remains prevalent only in Afghanistan and Pakistan. In September 2015, the WHO announced the eradication of type-2 poliovirus from the world and planned to adjust the trivalent oral Sabin vaccine into a bivalent vaccine (OPV1 and OPV3) in April of this year to prevent mutations in the oral vaccine that could lead to polio caused by vaccine-derived strains. 
A major polio epidemic occurred in Taiwan in 1982. Through the active promotion of inoculations with the oral Sabin vaccine by health units, since the following year, Taiwan has not further isolated wild poliovirus strains. Following more than 10 years of effort, in 2000, documents proving that polio has been eradicated in Taiwan were reported to the WHO. In coordination with the Global Polio Eradication Initiative and to reduce polio cases caused by live attenuated vaccines, beginning in September 2011, Taiwan switched comprehensively to the inactivated polio vaccine (IPV), preventing vaccine-derived strains generated through the use of the live attenuated vaccine from appearing. Currently, Taiwan retains only type-1 and type-3 polio Sabin vaccine strains used for laboratory quality control. After the global eradication targets are met, all of the polio vaccine strains will be destroyed. 
Polio is caused by the poliovirus, which spreads through the fecal-oral route. The virus can be detected in the throat secretions of the infected 36 hours after exposure. After 72 hours, the virus may be emitted through the excretion of fecal waste. For as long as 3 to 6 weeks, infectivity is extremely strong. More than 95% of the infected have no obvious symptoms or no symptoms at all. Fewer than 1% of the infected exhibit paralysis, but this can be prevented effectively through vaccines.