Polio reached a peak in the United States in 1952, with more than 21,000 paralytic cases.
The poliovirus is rapidly inactivated by heat, formaldehyde, chlorine, and ultraviolet light.
Up to 95% of all polio infections are inapparent or asymptomatic. [No symptoms.]
Approximately 4%–8% of polio infections consist of a minor, nonspecific illness without clinical or laboratory evidence of central nervous system invasion. This clinical presentation is known as abortive poliomyelitis, and is characterized by complete recovery in less than a week. Three syndromes observed with this form of poliovirus infection are upper respiratory tract infection (sore throat and fever), gastrointestinal disturbances (nausea, vomiting, abdominal pain, constipation or, rarely, diarrhea), and influenza-like illness. These syndromes are indistinguishable from other viral illnesses.
Nonparalytic aseptic meningitis (symptoms of stiffness of the neck, back, and/or legs), usually following several days after a prodrome similar to that of minor illness, occurs in 1%–2% of polio infections… Typically these symptoms will last from 2 to 10 days, followed by complete recovery.
Fewer than 1% of all polio infections result in flaccid paralysis.
Many persons with paralytic poliomyelitis recover completely and, in most, muscle function returns to some degree. Weakness or paralysis still present 12 months after onset is usually permanent.
The death-to-case ratio for paralytic polio is generally 2%–5%* among children and up to 15%–30% for adults (depending on age).
Person-to-person spread of poliovirus via the fecal-oral route is the most important route of transmission, although the oral-oral route may account for some cases.
In the immediate prevaccine era, improved sanitation allowed less frequent exposure and increased the age of primary infection.
From 1980 through 1999, a total of 152 confirmed cases of paralytic poliomyelitis were reported, an average of 8 cases per year… (95%) cases were vaccine-associated paralytic polio (VAPP) caused by live oral polio vaccine.
In order to eliminate VAPP from the United States, ACIP recommended in 2000 that IPV [inactivated polio vaccine] be used exclusively in the United States.
Because IPV contains trace amounts of streptomycin, polymyxin B, and neomycin, allergic reactions may occur in persons sensitive to these antibiotics.
Vaccine-associated paralytic polio is a rare adverse reaction following live oral poliovirus vaccine. Inactivated poliovirus vaccine does not contain live virus, so it cannot cause VAPP.