Minor Illness (Abortive Poliomyelitis)
The most common form of disease caused by poliovirus is
characterized by fever, malaise, drowsiness, headache, nausea,
vomiting, constipation, and sore throat in various combinations.
This manifestation has been estimated to occur in 4 to 8% of
infections. Even during an epidemic, the diagnosis of
poliomyelitis cannot be made with assurance on clinical
grounds, unless virus is isolated or antibody development is
measured. Many other viruses may cause the same signs and
symptoms and may circulate during the same seasons as poliovirus.
Aseptic Meningitis and/or Transient Mild Paresis
(Nonparalytic Poliomyelitis)
In addition to the symptoms and signs of abortive poliomyelitis,
the patient has stiffness and pain in the back and neck.
Occasionally, there is mild muscle weakness or transient paralysis.
The disease lasts 2 to 10 days, and recovery is almost
always complete. About 1 or 2% of infections take this course
during epidemics. In a small percentage of cases, meningitis
advances to paralysis. It should be noted that a number of
other viruses, particularly other members of the enterovirus
family, also produce this syndrome.
Paralytic Poliomyelitis
The major illness constitutes the manifestations listed above
for aseptic meningitis plus persisting weakness of one or more
muscle groups, either skeletal or cranial. It accounts for about
1% of poliovirus infections. The onset of paralysis may follow
the minor illness after a symptom-free interlude or may occur
without an antecedent phase of illness. The predominating sign
is flaccid paralysis resulting from lower motor neuron damage.
Incoordination secondary to brain stem invasion may also occur,
and there may be painful spasms of nonparalyzed muscles.
The amount of damage varies widely. Usually, muscle involvement
is maximal within a few days after the paralytic phase
begins. Maximal recovery usually occurs within 6 months, with
residual paralysis lasting much longer, often for life.
