Paediatrics chapters
Poliomyelitis and AFP surveillance
Poliomyelitis in children: how poliovirus spreads, the range from silent infection to paralytic and bulbar polio, how to recognise and report acute flaccid paralysis, the vaccines and schedule, supportive care and long-term rehabilitation.
- Poliovirus (an enterovirus, types 1, 2, 3; humans the only reservoir) spreads mainly faecal-orally; over 90% of infections are silent, a few cause a minor illness or aseptic meningitis, and under 1% cause paralytic polio: fever then acute, asymmetric, flaccid paralysis, proximal more than distal, reflexes lost, sensation normal, from damage to anterior horn cells; bulbar polio causes most deaths.
- Every child under 15 years with acute flaccid paralysis must be reported and have two stool samples 24-48 hours apart within 14 days of onset, sent cold, with a 60-day follow-up for residual paralysis.
- Prevention is vaccination: OPV (live, gut immunity, herd effect, rare VAPP) and IPV (injected, safe in immunodeficiency); care is supportive (rest, positioning, no IM injections, respiratory watch) then physiotherapy, splints and callipers.
On this page
Overview
Poliomyelitis is an acute viral infection that, in a small minority, destroys lower motor neurones and leaves a child with permanent, asymmetric flaccid paralysis. It is preventable by vaccine and is the target of a global eradication effort. Park lists Pakistan among the last countries where wild poliovirus has never been interrupted, so acute flaccid paralysis (AFP) surveillance is a duty for every doctor here. Exam questions test transmission, the clinical forms, AFP reporting, the two vaccines and long-term care.
Virus and transmission
- Poliovirus: a small RNA enterovirus with three serotypes (1, 2, 3). Immunity to one type does not fully protect against the others.
- Type 1 causes most paralytic outbreaks (Park). Wild type 2 was declared eradicated in 1999.
- Humans are the only reservoir; there are no chronic carriers and no animal source.
- Routes:
- Faecal-oral: the main route where sanitation is poor (hands, water, food, flies).
- Droplet spread from the throat early in the illness.
- Incubation: usually 7-14 days (range 3-35); Akbar gives 8-12 days to the onset of paralysis.
- Infectivity: greatest just before and after onset. Virus stays in the throat for about 1 week and is excreted in faeces for several weeks, sometimes months.
- Age: mainly infants and young children; Park gives 6 months to 3 years as the most vulnerable age. Maternal antibody protects for the first few months.
- Provoking factors for paralysis in an infected child: fatigue, trauma, intramuscular injections, tonsillectomy (Park).
For every paralytic case there are many silent infections (Park estimates about 1,000 subclinical infections per case in children). Silent carriers, not paralysed children, keep the virus circulating.
Pathogenesis
- Virus enters by mouth and multiplies in the pharynx and gut (Peyer's patches, regional nodes).
- A brief viraemia follows.
- If antibody neutralises the virus, no illness or only a minor illness occurs.
- Otherwise the virus reaches the CNS and destroys motor neurones, mainly the anterior horn cells of the spinal cord, and also motor nuclei in the medulla (bulbar polio), cerebellum and motor cortex.
Local secretory IgA in the gut is a key defence against reinfection; serum antibody prevents spread to the nervous system.
Clinical diagnosis
Spectrum of infection
| Form | Frequency | Features |
|---|---|---|
| Inapparent (silent) | Over 90% | No symptoms; detected only by virus isolation or antibody rise |
| Abortive (minor illness) | About 5% | Brief fever (rarely above 39.5°C), malaise, sore throat, headache, vomiting, abdominal pain; full recovery |
| Non-paralytic (aseptic meningitis) | About 1% | Minor illness, a few days without symptoms, then fever, headache, neck and back stiffness; recovers |
| Paralytic | Under 1% | Meningitic phase followed by flaccid paralysis |
Non-paralytic polio: signs of meningeal irritation
- Neck and spinal stiffness; Kernig and Brudzinski signs.
- Tripod sign: the child sits only by propping on hands behind the back with hips and knees partly bent.
- "Kiss-the-knee" test: cannot touch the knee with the lips.
- Superficial reflexes (abdominal, cremasteric) fade first, then tendon reflexes change, warning of coming paralysis.
Paralytic polio
- Fever at the onset of paralysis strongly suggests polio.
- Paralysis is:
- Acute and reaches its maximum within a few days, usually by the time the fever settles.
- Asymmetric and patchy; proximal muscles (hip, shoulder) more than distal; legs more than arms.
- Flaccid, with lost tendon reflexes.
- Without sensory loss.
- Muscle pain and spasm are common early; bladder paralysis and constipation may occur.
Forms of paralytic polio
| Form | Features |
|---|---|
| Spinal | Limbs, trunk, neck, abdomen; diaphragm and intercostal weakness causes respiratory failure |
| Bulbar | Cranial nerves IX, X and XII: nasal voice, nasal regurgitation, pooling of saliva, weak cough, deviated uvula or tongue, hoarseness; medullary centres: irregular breathing, blood pressure swings; causes most deaths |
| Bulbospinal | Both together |
| Encephalitic | Uncommon; irritability, confusion, drowsiness, tremor |
"Fever, flaccid, few limbs, feeling fine": fever at onset, flaccid asymmetric weakness of a few limbs, sensation intact.
Investigations
- Stool culture for poliovirus: the test of choice. Two or more samples at least 24 hours apart, as early as possible and within 14 days of onset.
- Virus can also be grown from the throat early, and from CSF for a few days in meningitis.
- CSF: up to several hundred cells, mostly lymphocytes, normal glucose, mildly raised protein.
- The laboratory separates wild from vaccine-related virus by genetic tests.
Differential diagnosis of acute flaccid paralysis
| Condition | Clues against polio |
|---|---|
| Guillain-Barre syndrome | Symmetric, ascending weakness, often sensory symptoms, no fever at onset, high CSF protein with few cells |
| Transverse myelitis | Sensory level, bladder involvement, both legs together |
| Traumatic neuritis | Follows an IM injection into the buttock; one leg |
| Botulism | Descending, symmetric, cranial nerves first, dilated pupils, afebrile |
| Others | Tick paralysis, hypokalaemia, diphtheritic neuropathy, pseudoparalysis from bone or joint infection |
Guillain-Barre gives symmetric weakness and high protein with normal cells; polio gives asymmetric weakness with fever and a lymphocytic CSF. Both are flaccid and areflexic, so all must still be reported as AFP.
Polio damages the lower motor neurone, so expect flaccid weakness, wasting and absent reflexes; spasticity, sensory loss or a sensory level point to another cause.
Acute flaccid paralysis surveillance
Surveillance finds every possible polio case, even where polio is no longer seen. Park describes four steps.
1. Find and report
- Report every child under 15 years with acute flaccid paralysis, whatever the doctor thinks the cause is, and any person of any age in whom polio is suspected.
- Health facilities send regular reports, including "zero" reports when no case is seen; staff also search hospital records actively.
2. Collect and transport stool
- Two stool samples, 24-48 hours apart, as soon as possible and within 14 days of paralysis onset (virus excretion is highest in the first two weeks).
- Seal and keep cold at 4-8°C (reverse cold chain); they should reach the laboratory within 72 hours.
3. Isolate the virus
A WHO-accredited laboratory isolates poliovirus and separates wild from vaccine strains.
4. Map the virus
Genetic sequencing shows where the virus came from and guides vaccination campaigns.
Quality targets (Park)
| Indicator | Target |
|---|---|
| Non-polio AFP rate | At least 1 per 100,000 children under 15 each year (2 per 100,000 in endemic areas) |
| Adequate stool collection | At least 80% of AFP cases |
| Follow-up examination | At least 80% checked for residual paralysis at 60 days |
| Reporting completeness | At least 80% of reports on time |
Environmental surveillance (testing sewage) supplements AFP surveillance and can detect virus without any paralysed case.
The non-polio AFP rate measures how sensitive the surveillance system is: a country that finds fewer than the target number of AFP cases is probably missing cases rather than truly clear of polio.
Vaccine types and schedule
| Feature | OPV (Sabin) | IPV (Salk) |
|---|---|---|
| Vaccine | Live attenuated, oral drops | Inactivated (formalin), IM injection |
| Gut (secretory IgA) immunity | Yes: stops wild virus multiplying in the gut | Little; protects the person from paralysis but not the gut |
| Herd effect | Yes: vaccine virus spreads to contacts | No |
| Use in outbreaks | Yes: mass campaigns | Not suitable alone |
| Main risk | Vaccine-associated paralytic polio (VAPP) and vaccine-derived poliovirus | None serious |
| Immunodeficient child or household contact | Avoid | Use |
| Cost and handling | Cheap, easy; very heat-sensitive (kept frozen) | Costlier; needs trained staff |
- VAPP: Akbar puts it at about 1 in 6 million OPV doses; it can affect vaccine recipients and their contacts. Children with antibody deficiency (for example X-linked agammaglobulinaemia) are at risk from OPV (Nelson).
- Vaccine-derived poliovirus (VDPV): vaccine virus that has circulated for long and regained neurovirulence; it needs the same response as wild virus.
- OPV is not withheld for breastfeeding or mild illness; a dose given during diarrhoea is not counted and is repeated.
Schedule in Pakistan
The routine EPI gives OPV at birth (OPV-0), 6, 10 and 14 weeks, with IPV at 14 weeks and a second IPV dose at 9 months, plus OPV in national campaigns. The schedule is set by the Federal Directorate of Immunization (EPI Pakistan) (checked 8 Nov 2026) and can change; check the current national guideline. Global eradication updates: WHO poliomyelitis fact sheet (checked 8 Nov 2026).
Supportive care
There is no antiviral treatment; good care limits paralysis and deformity.
Abortive polio
Rest, analgesics and a good diet at home.
Paralytic polio (hospital)
- Strict bed rest in a neutral position: feet at a right angle, knees slightly bent, hips and spine straight, held with sandbags.
- Minimal handling of affected limbs.
- No intramuscular injections (they can provoke or worsen paralysis).
- Analgesics and mild sedation; warm (hot) packs relieve muscle pain and spasm.
- Watch breathing closely: anxiety, restlessness and fatigue signal respiratory failure; check blood pressure at least twice daily.
- Bulbar polio: keep the airway clear with suction; nurse prone or on one side, head low to prevent aspiration; tube feed if swallowing fails; ventilate for respiratory paralysis.
- Hydration, nutrition, bladder care and prevention of constipation and pressure sores.
Long-term complications and rehabilitation
Complications
- Permanent asymmetric weakness and muscle wasting; Akbar says permanent paralysis follows in about 15% of paralytic cases, with mortality of 5-10%.
- Contractures and deformities, limb-length discrepancy, scoliosis.
- Respiratory, swallowing, bladder and bowel dysfunction.
- From immobility: hypercalcaemia, nephrocalcinosis, pressure sores.
- Post-polio syndrome: years later (Akbar: 30-40 years), new muscle pain, fatigue and weakness.
Wide paralysis during the first 10 days predicts a worse final disability. Some recovery occurs over the first 6 months; weakness left after that usually persists.
Rehabilitation
- Physiotherapy as soon as the acute stage is over: strengthening, stretching to prevent contractures.
- Splints, braces and callipers to support weak limbs and allow walking.
- Orthopaedic surgery occasionally for fixed deformity or limb-length problems.
- Schooling, family support and vocational help.
- A child who has had polio still needs full vaccination (other serotypes).
Expect: poliovirus as an enterovirus with three types, humans as the only reservoir and faecal-oral spread; the spectrum from silent infection (over 90%) to paralytic polio (under 1%); anterior horn cell damage causing acute, asymmetric, flaccid, areflexic paralysis without sensory loss, with fever at onset; bulbar polio causing most deaths; stool culture as the diagnostic test; AFP surveillance in all children under 15 with two stool samples 24-48 hours apart within 14 days, cold chain, 60-day follow-up and a non-polio AFP rate of at least 1 per 100,000; OPV versus IPV, VAPP and vaccine-derived virus; no IM injections, positioning and respiratory care; physiotherapy, callipers and post-polio syndrome.
Quick revision
- Enterovirus types 1, 2, 3; man only reservoir; faecal-oral; incubation about 1-2 weeks.
- Over 90% silent; about 1% meningitic; under 1% paralytic.
- Anterior horn cells: fever, asymmetric proximal flaccid paralysis, areflexia, sensation normal.
- Bulbar (IX, X, XII): nasal voice, regurgitation, respiratory failure; most deaths.
- Stool culture × 2, 24-48 h apart, within 14 days; CSF lymphocytes, mild protein rise.
- AFP: report every child under 15; cold chain; lab within 72 hours; 60-day follow-up.
- OPV: gut immunity, herd effect, VAPP; IPV: safe in immunodeficiency.
- Care: rest, positioning, no IM injections, airway; then physiotherapy, callipers.
Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics; Park's Preventive and Social Medicine).
FAQ
Why must every case of acute flaccid paralysis be reported, even if it looks like Guillain-Barre syndrome?
Early polio can resemble other causes, and only stool testing can exclude it. Reporting all AFP in children under 15 also measures whether the surveillance system is sensitive enough.
Why are injections avoided in a child with suspected polio?
Intramuscular injections during the illness can provoke or worsen paralysis in the injected limb, and injection injury can itself cause flaccid weakness.
Why is OPV still used when IPV cannot cause paralysis?
OPV gives gut immunity and spreads to contacts, so it stops wild virus circulating in the community and is cheap and easy to give in campaigns; IPV protects the individual but does little to stop transmission.
Does a child who has recovered from polio need the vaccine?
Yes. Infection protects only against the type that caused it, so full vaccination against all types is still needed.