Poliovirus infection (Poliomyelitis, Infantile paralysis)

Page 1 2 3

What is Poliovirus infection?

A Poliovirus infection affects the nervous system, in particular the anterior horn cells of the spinal cord and cranial nerve motor neurones.

Poliovirus may cause one of four clinical syndromes:

1) Asymptomatic infection: viral infection not causing any symptoms - 90% of cases.
2) Abortive poliomyelitis: minor illness. Non-specific symptoms due to a viral illness such as fever, malaise, headache, sore throat.Occurs in 5%.
3) Nonparalytic poliomyelitis: aseptic meningitis, occurring in 1-2%.
4) Paralytic polio: the most severe syndrome causing spinal or bulbar (cranial nerve) paralysis - affects 0.1 to 2% of cases.

Who gets Poliovirus infection?

Poloimyelitis (polio) is found worldwide but its prevalence has decreased dramatically following improvements in sanitation, hygiene and the wide-spread use of polio vaccines.

Polio is typically a childhood disease, but can occur at any age.

Predisposing Factors

The virus is excreted in faeces and usually spread via the faecal-oral route.

Predisposing factors for contracting the illness are:

not vaccinating young children at the recommended age.
a very small proportion of cases occur as a result of the vaccination itself (due to the attenuated vaccine) although most cases result from lack of vaccination.

Progression

Polio has an incubation period of 7-14 days. Paralysis with no sensory loss has a subacute onset, although the degree can vary from involving only a few muscle groups, or as much as all four limbs. The paralysis can progress over the first few days, and subsequently it can either completely recover, or result in residual paralysis, or lead to death. Bulbar polio (affecting the brain stem and cranial nerves) is especially severe because it can affect the vocal cords and pharynx.

Recovery usually takes around 6 months but can be up to 2 years.

Page 1 2 3