Polio Facts (cont.)

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What causes polio?

Polio is caused by small RNA viruses. They are members of the enterovirus group of the Picornavirus family. There are three types (types 1, 2, and 3) of polio viruses; type I is responsible for about 85% of all paralytic infections. These types are antigenically distinct strains of viruses; infection or immunity to one type does not protect against the other two types, however, if immunity is established to one or all of the three strains, immunity is lifelong. The problem that these viruses cause is the destruction of spinal cord cells (specifically, the anterior horn cells).

What are risk factors for polio? How does polio spread?

Currently, the World Health Organization (WHO) have certified that the Americas, Western Pacific, and Europe are polio free; other areas have a low incidence of polio, but people in war zones where vaccinations have been interrupted are at a risk getting polio (for example, Afghanistan and Syria). The greatest risk factor for polio is not being vaccinated. People with immunodeficiency (HIV, cancer patients, chemotherapy patients, for example), very young individuals, pregnant females, caregivers for polio patients, travelers to areas were polio is endemic, and lab personnel who work with live polioviruses are at increased risk for polio.

Polio, like smallpox, only infects humans. Polio spreads by person-to-person contact; the virus lives in the throat and in the intestines; polio is spread through contact with the feces or by droplet spread in a sneeze or cough. It can also be spread by an infected person who has contaminated food or fluids by touching or tasting them. Unfortunately, a person can be infectious and transmit the virus even before they develop any symptoms.

Medically Reviewed by a Doctor on 4/4/2014


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