The CDC recently opened an investigation into an epidemic of Acute Flacid Paralysis but the cause is well known. The oral polio vaccine (OPV) not only protected against polio but other polio like entrovirus infections. The cessation of this vaccine without any other protective vaccine has caused the epidemic paralysis. The development of a hand and foot disease vaccine like the one licensed in China might potentially solve this problem.
In the meantime scientists have long known of the cause of this epidemic.