- Reason for surveillance
- Case definition
- Notification criteria and procedure
- The disease
- Managing single notifications
1. Reason for surveillance
To identify cases, and so prevent further spread.
2. Case definition
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.
As for a confirmed case (see below).
A confirmed case requires:
- Laboratory definitive evidence, and
- Clinical 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).
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.
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 NCIMS.
4. The disease
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 (droplet transmission). In areas of poor sanitation, the disease is usually spread through the faecal-oral route.
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. Infectiousness is greatest for the 7 to 10 days before and after onset of symptoms.
Asymptomatic cases are also infectious.
The vast majority (>95%) of polio infections are asymptomatic.
Abortive poliomyelitis is characterized by fever, headache, sore throat, listlessness, anorexia, vomiting, or abdominal pain. There are no neurological signs.
Non-paralytic poliomyelitis is similar to abortive poliomyelitis but the case also displays meningeal irritation (but not paralysis).
Acute flaccid paralysis occurs in 0.1% to 2% of cases. Some report a 1-3 day long viral illness in the preceding week with apparent full recovery for 2-5 days before the onset of paralysis.
There is typically a fever, chills, headache, malaise, vomiting, neck stiffness, and cerebrospinal fluid (CSF) pleocytosis. There is severe myalgias and cutaneous hyperesthesia, paresthesias, involuntary muscle spasm, or muscular fasciculations.
Severity of weakness varies from weakness of one muscle group to complete quadriplegia. Paralysis is flaccid; tendon reflexes are initially increased and then absent. Paralysis is typically asymmetric with legs more commonly affected than arms. Commonly paralysis develops over a period of 2-3 days (sometimes shorter).
Sensory loss is very rare and suggests an alternative cause.
Cranial nerve involvement and paralysis of respiratory muscles can occur.
5. Managing single notifications
Immediately on notification of a probable or confirmed case begin follow-up investigation and notify the Communicable Diseases Branch.
Within 1 working day of notification enter confirmed and probable cases on NCIMS.
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
Investigation and treatment
Treatment is supportive only and cases may require management in intensive care.
Appropriate stool specimens should be collected from all cases of acute flaccid paralysis in children irrespective of the provisional diagnosis in order to exclude polio as the cause.
The polio reference laboratory at VIDRL is able to differentiate vaccine associated paralytic poliomyelitis (VAPP), circulating vaccine-derived poliovirus (cVDPV) or imported wild-type poliovirus.
- 2 stool samples collected within 14 days of onset are required.
- The second sample must be taken ≥24 hours after the first.
- Details about the laboratory's specimen packaging requirements and contact details are available at Acute Flaccid Paralysis (AFP) Surveillance.
Ensure that acute and convalescent (3 weeks later) serum samples are collected and sent for serological testing.
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, flight details
- Whether the case attends a workplace, school or other institution.
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 droplet precautions.
In communities with appropriate modern sewerage systems, faeces from infected patients can be disposed of directly into sewers without preliminary disinfection. Terminal disinfection is required for all other potentially contaminated items.
Note that PD2011_005 Occupational assessment, screening and vaccination against specified infectious diseases does not currently include polio as a specified infectious disease and health care workers should not be assumed to be immune.
The case must not attend school/institution/work for at least 14 days from onset and until the case has fully recovered.
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.
Note that any susceptible contacts may already have been infected by the time the first case is recognised.
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 immunisation status of all contacts' and immunise as appropriate.
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 significant 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.
Advise susceptible contacts of the clinical features (including asymptomatic infection), the risk of infection and the mode of transmission. Optimise uptake of primary or booster immunisation as appropriate.
Contacts should be advised about the importance of hand washing, covering the mouth when coughing, sneezing into disposable tissues, and the appropriate cleaning or disposal of contaminated objects.
Isolation and restriction
Because many susceptible contacts may already be infected by the time the case has been diagnosed (usually asymptomatically) it may be necessary to restrict them from working in certain high risk occupations (eg food handling, health care, childcare) until they are known not to be infectious.