POLIOMYELITIS

Last updated: 06 September 2004

1. Reason for surveillance

• To identify cases, and so prevent further spread.

2. Case definition

Probable case
A probable case of poliomyelitis requires:

• Clinical evidence due to wild-type poliovirus, and

• The case not discarded as non-polio acute flaccid paralysis by the Polio Expert Committee.

Laboratory evidence
Not applicable

Clinical evidence
As for a confirmed case (see below).

Epidemiological evidence
Not applicable.

Confirmed Case
A confirmed case requires:

• Laboratory definitive evidence, and

• Clinical evidence.

Laboratory evidence
Wild-type polio infection:

• Isolation of wild poliovirus (confirmed in the WHO Western Pacific Regional Poliovirus Reference Laboratory), or

• Detection of wild-type poliovirus by NAT (confirmed in the WHO Western Pacific Regional Poliovirus Reference Laboratory).

Vaccine associated poliomyelitis:

• Isolation of Sabin-like poliovirus from a clinical specimen (confirmed in the WHO Western Pacific Regional Poliovirus Reference Laboratory), or

• Detection of Sabin-like poliovirus by NAT (confirmed in the WHO Western Pacific Regional Poliovirus Reference Laboratory).

Clinical evidence
Acute flaccid paralysis: acute onset of progressive weakness and flaccidity of one or more limbs with decreased or absent tendon reflexes in the affected limbs or bulbar palsy without other apparent cause, and without sensory or cognitive loss.

Epidemiological evidence
Not applicable.

Factors to be considered in case identification
Poliomyelitis is diagnosed by isolation of the virus in cell culture or by NAT in specimens of CSF, faeces or oropharyngeal secretions. The likelihood of poliovirus isolation is highest from stools, intermediate from pharynx, and very low from blood or spinal fluid.

Distinguishing between wild and vaccine strains should be done by the WHO Western Pacific Regional Poliovirus Reference Laboratory at the Victorian Infectious Diseases Reference Laboratory (VIDRL).

Serology does not distinguish vaccine-induced immunity from wild virus infections, but may help support the diagnosis. A ≥4-fold rise between acute and convalescent sera (≥3 weeks apart) suggests infection, but may be false negative if the patient is immunocompromised or if antibodies (which appear early in the infection) were already elevated when the acute sera were drawn.

3. Notification criteria and procedure

Poliomyelitis is to be notified by:

• Hospital CEOs on clinical diagnosis (ideal reporting by telephone within one hour of diagnosis)

• Laboratories on microbiological confirmation (ideal reporting by telephone within one hour of diagnosis)

• School principals and directors of child care facilities (ideal reporting by telephone within one hour of notification.)

Both probable and confirmed cases should be entered on NDD.

4. The disease

Infectious agents
The Enterovirus poliovirus, types 1, 2 and 3.

Mode of transmission
Poliomyelitis is transmitted primarily by person-to-person spread. Where sanitation is good, pharyngeal transmission is the most important method. In areas of poor sanitation, the disease is usually spread through the faecal-oral route.

Timeline
The typical incubation period is 7 to 14 days for paralytic cases, with a possible range of 3 to 35 days. Poliomyelitis is communicable as long as the virus is excreted, that is approximately 1 week in the pharynx and up to 6 weeks in the faeces. Risk of infection is greatest for the 7 to 10 days before and after onset of symptoms.

Clinical presentation
The clinical presentations range from inapparent infection, through non- pecific febrile illness, aseptic meningitis, paralytic disease and death. When symptoms occur they include fever, malaise, headache, nausea, vomiting, muscle pain, neck and back stiffness with or without flaccid paralysis.

5. Managing single notifications

Response times
Investigation
Immediately on notification of a probable or confirmed case begin follow-up investigation and notify the Communicable Diseases Branch.

Data entry
Within 1 working day of notification enter confirmed and probable cases on NDD.

Response procedure
The response to a notification will normally be carried out in collaboration with the case's health carers. But regardless of who does the follow-up, PHU staff should ensure that action has been taken to:

• Confirm the onset date and symptoms of the illness

• Confirm results of relevant pathology tests, or recommend the tests be done

• Find out if the case or relevant care-giver has been told what the diagnosis is before beginning the interview

• Seek the doctor's permission to contact the case or relevant care-giver

• Review case and contact management

• Prevent further spread

Case management
Investigation and treatment
Ensure that 2 stool samples are taken ≥24 hours apart 0- 14 days after onset of paralysis, and that they arrive at the laboratory with ice present (or still-frozen ice packs) to determine if it is a wild or vaccine strain.

Ensure that acute and convalescent (3 weeks later) serum samples are collected and analysed.

Information should be collected on:

• The case's demographics

• Place, time, source and type of any polio immunisations

• Clinical details, including date of onset, complications, and immunosuppression

• Lab test results

• Contact with other cases or travellers, travel history and persons at risk for polio

• Whether the case attends a school or other institution.

Treatment is supportive only.

Investigation and treatment
The case or relevant care giver should be informed about the nature of the infection and the mode of transmission.

Isolation and restriction
Cases are isolated in hospital with standard precautions. Advise case not to attend school/institution/work for at least 14 days from onset and until the treating doctor can confirm in writing that the case has recovered.

Environmental evaluation
Nil

Contact management
Identification of contacts
A contact is defined as any person at the same institution (such as a school or child care facility) or with household, work or social contact with the case.

Investigation and treatment
Thoroughly search for other cases, especially children, to assure early detection and to facilitate control and permit appropriate treatment of unrecognised and unreported cases.

Check and update if necessary contacts' immunisation status.

Passive immunisation
None

Active immunisation
Depending on whether the case was acquired locally or overseas, and the likely immunisation coverage in the community, vaccination of at risk populations should be considered in response to a single case of wild polio. A large vaccine campaign may be indicated involving 2 rounds of polio vaccine 4 weeks apart for all children <5 years old regardless of immunisation status. Strategies should be determined in conjunction with an expert committee established by CDB.

Antibiotic prophylaxis
None.

Education
Advise susceptible contacts (or parents/guardians) of the risk of infection.

Isolation and restriction
None