Viruses cause many diseases in humans, animals and plants.
Polio Viral poliomyelitis is now very rare in developed countries due to the success of vaccination programs. Unfortunately polio is still a common illness in developing countries. Infectious polio virus is excreted in the faeces where it can spread to the sewage and water supplies. Two different types of polio vaccine are in widespread use and have saved literally hundreds of thousands of lives. The Sabin polio virus replicates slowly in the intestine ensuring the rapid generation of a strong host immune response.