Polio is an acute viral disease that usually affects children and young adults, caused by one of three polioviruses. It can be transmitted through direct contact with an infected person, or indirect contact with infected mucus, phlegm, or feces. The disease may cause no symptoms or mild symptoms like headache and muscle pain. In more severe cases, it can cause paralysis or breathing problems. Prevention includes vaccination and hygiene practices to avoid contact with infected bodily fluids.