Poliomyeletis

The most recognizable feature of poliomyelitis is onset of acute flaccid paralysis (AFP)

AFP, when it occurs, is of gradual onset (2–4 days); typically asymmetric and usually involves lower rather than upper limbs. Bulbar (brainstem) paralysis leading to respiratory depressions accounts for the 2–10% mortality rate associated with paralytic poliomyelitis. After the acute illness, there is often a degree of recovery of muscle function; 80% of eventual recovery is attained within 6 months, although recovery of muscle function may continue for up to 2 years.

Symptoms

This symptom occurs in less than 1% of Poliovirus infections. More than 90% of those infected have asymptomatic infections or a mild, non- specific febrile illness that lasts a few days. An abrupt onset of meningitic and neuromuscular symptoms, such as neck stiffness and pain in the limbs follow in a few cases, associated with fatigue, headache, vomiting and constipation (or less commonly, diarrhoea).

After many years of stable neurological impairment, new neuromuscular symptoms (post-polio syndrome) may develop in 25–40% of patients.

Infectious Agents

The infectious agent is Poliovirus (of the Enterovirus genus group). Types 1, 2 and 3 can all cause paralysis. Type 1 is the type most often isolated from paralytic cases and associated with epidemics. Most vaccine-associated cases are classified as type 2 or 3.

Mode of transmission

Poliovirus is transmitted mainly via the faecal–oral route.

Prevention

Immunization is vital for the prevention of poliomyelitis.

Polio reported cases. Geneva, World Health Organization (WHO), 2010 (Poliomyelitis – number of reported cases (who.int)).
Cessation of Trivalent Oral Poliovirus Vaccine and Introduction of Inactivated Poliovirus Vaccine — Worldwide, 2016(Cessation of Trivalent Oral Poliovirus Vaccine and Introduction of Inactivated Poliovirus Vaccine — Worldwide, 2016 | MMWR (cdc.gov)).