Polio, often called polio or infantile paralysis, is an infectious disease caused by the poliovirus. In approximately 0.5% of cases there is muscle weakness resulting in an inability to move. This can happen from a few hours to a few days. The weakness most often affects the legs, but may less commonly involve the muscles of the head, neck, and diaphragm.
Many, but not all people make a full recovery. In those with muscle weakness between 2% and 5% of children and 15% to 30% of adults die. Another 25% of people have minor symptoms such as fever and a sore throat, and up to 5% have headaches, stiff neck, and pain in the arms and legs. These people are usually back to normal within a week or two. In up to 70% of infections there are no symptoms. Years after recovery from post-polio syndrome can occur, with a slow development of muscle weakness similar to what the person had during the initial infection.
Poliovirus usually spreads from person to person through infected fecal matter entering the mouth. It can also be spread by food or water that contains human feces and less commonly by infected saliva. Those who are infected can spread the disease for up to six weeks, even if there are no symptoms. The disease can be diagnosed by finding the virus in the stool or by detecting antibodies to it in the blood. The disease only occurs naturally in humans.
The disease can be prevented with the polio vaccine; However, multiple doses are required for it to be effective. The US Centers for Disease Control and Prevention recommends increasing polio vaccination for travelers and those living in countries where the disease is occurring. Once infected there is no specific treatment. In 2016, polio affected 42 people, while in 1988 there were about 350,000 cases. In 2014, the disease was only spreading among people in Afghanistan, Nigeria, and Pakistan. In 2015, Nigeria had stopped the spread of wild poliovirus, but it was resorted in 2016.
Polio has been around for thousands of years, with depictions of the disease in ancient art. The disease was first recognized as a distinct condition by Michael Underwood in 1789 and the virus that causes it was first identified in 1908 by Karl Landsteiner. The main outbreaks began to occur in the late 19th century in Europe and the United States. In the 20th century it became one of the most worrisome childhood illnesses in these areas. The first polio vaccine was developed in the 1950s by Jonas Salk. Vaccination efforts and early detection of cases are expected to result in global eradication of the disease by 2018.
