Poliomyelitis is spread mainly by fecal-oral transmission and can be prevented in children by vaccination. Poliomyelitis is an acute infectious disease mainly caused by poliovirus infection. Humans are the only known natural host of the poliovirus, and the virus mainly affects children under 5 years of age. Poliovirus is mainly transmitted by the fecal-oral route, when the virus enters the intestines through the mouth it multiplies in the intestines. Clinically, the disease is often seen as a latent polio infection with no symptoms; however, some patients may develop flaccid paralysis of the limbs as a result of the virus attacking the nervous system. There is no effective treatment for this disease, but it can be prevented by polio vaccination.