Poliovirus

Background

Single-stranded, positive-sense, unenveloped RNA virus in the family Picornaviridae, genus Enterovirus, species Enterovirus C
Currently, the most common cause of poliomyelitis is oral vaccine-derived poliovirus

90-95% of cases are clinically inapparent; 4-8% are abortive after the prodrome; and only 1-2% proceed to major illness
Incubation period of 9 to 12 days (range 5 to 35 days) before onset of prodrome
Minor illness lasts a few days
- Fever, headache, sore throat, malaise, anorexia, vomiting, or abdominal pain
- Normal neurological exam

0.1% of all poliovirus infection
2 to 5 days after resolution of minor illness, onset of aseptic meningitis, with fever, headache, nuchal rigidity, vomiting, and a CSF pleocytosis
Weakness and paralysis start within a few days
- Asymmetric, flaccid paralysis with increased DTRs
- Typically proximal more than distal muscles, and legs more than arms
- Typical pattern is one leg then one arm, or both legs then both arms
- Progresses to complete paralysis over 2 to 3 days
Rarely sensory loss; if present, consider another diagnosis such as Guillain-Barré syndrome

Represents 5 to 25% of paralytic poliomyelitis during outbreaks
Affects the cranial nerves, presenting with dysphagia, nasal speech, and dyspnea
Pooling saliva

Paralytic poliomyelitis: other causes of acute flaccid paralysis
- Other enteroviruses, such as enterovirus A-71, enterovirus D-68
- West Nile virus
- Guillain-Barré syndrome, which would be symmetrical, bilateral ascending paralysis with loss of sensation, that progresses over 1 to 2 week and has minimal CSF pleocytosis with albuminocytologic dissociation
Polioencephalitis: other causes of encephalitis

PCR is the only way to distinguish between wildtype polio and vaccine-derived
- Throat swabs during the first week of illness
- Feces for several weeks
- CSF not particularly sensitive, but is helpful when positive and should still be sent
Acute and convalescent serology