Poliovirus infection (Poliomyelitis, Infantile paralysis)

What is Poliovirus infection?
Statistics on Poliovirus infection
Risk Factors for Poliovirus infection
Progression of Poliovirus infection
How is Poliovirus infection Diagnosed?
Prognosis of Poliovirus infection
How is Poliovirus infection Treated?
Poliovirus infection References

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.

Statistics on 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.

Risk Factors for Poliovirus infection

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 of Poliovirus infection

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.

How is Poliovirus infection Diagnosed?

General investigations are not useful in diagnosing poliomyelitis.

Prognosis of Poliovirus infection

The outcome varies with the form (subclinical, nonparalytic, or paralytic) and the site affected. If the spinal cord and brain are not affected, which occurs in over 90% of cases, complete recovery is likely. Bulbar polio has a poor prognosis - can lead to death in around 75% of cases.Brain or spinal cord involvement is a medical emergency that may result in paralysis or death (usually from respiratory difficulties). Disability is more common than death. Lesions high in the spinal cord or in the brain are associated with greater risk for respiratory difficulty.

How is Poliovirus infection Treated?

There must be bed rest during the early course of the illness. Respiratory support with intermittent positive-pressure respiration may be requires if the muscles of respiration are involved. Once the acute phase of the illness has subsided, patient rehabilitation may take place including occupational therapy, physiotherapy and occassionally surgery.Immunisation by an active virus is can currently be used to prevent and control the disease. Occasionally an inactivated intramuscular vaccine is used for immunocompromised patients and pregnant women.

Poliovirus infection References

[1] Kumar P, Clark M. Clinical Medicine. Fourth Ed. WB Saunders, 2002.[2] Murray PR., Rosenthal KS., Kobayashi GS., Pfaller MA., Medical Microbiology, 3rd Ed, Mosby 1998.