Polio is a viral disease which may affect the central nervous system. Since polio immunization has become widespread, cases of polio are very rare.
Polio is more common in infants and young children and occurs under conditions of poor hygiene. However, paralysis is more common and more severe when infection occurs in older individuals. In exceedingly rare cases, oral polio vaccine can cause paralytic polio in a person who receives the vaccine and in a person who is a close contact of a vaccine recipient (one in every 8.1 million doses and one in every 5 million doses, respectively).
Polio is predominately spread through the feces.
Infection ranges in severity from an inapparent infection to a paralytic disease which may result in death. Symptoms include fever, malaise, headache, nausea and vomiting, excruciating muscle pain and stiffness in the neck and back.
The incubation period is usually six to 20 days for paralytic cases, with a range of three to 35 days.
Patients are most infectious from seven to 10 days before and after the onset of symptoms. However, patients are potentially contagious as long as the virus is present in the throat and feces. The virus persists in the throat for approximately one week after the onset of illness and is excreted in the feces for several weeks or, occasionally months.
There are three types of polio virus. Lifelong immunity usually depends on which type of virus a person contracts. Second attacks are rare and result from infection with a polio virus of a different type than the first attack.
There is presently no cure for polio. Treatment involves supportive care.
Complications include paralysis (most commonly of the legs). Paralysis of the muscles of respiration and swallowing can be fatal.
Two types of polio vaccine are available: trivalent oral polio vaccine (TOPV) and inactivated polio vaccine (IPV). The American Academy of Pediatrics and the Advisory Committee on Immunization Practices recommend that TOPV be given at two, four and 15 months of age and between four and six years of age.
- South Dakota Department of Health, Immunization Program
- Centers for Disease Control and Prevention