Poliomyelitis

Notification requirements for poliomyelitis

Poliomyelitis is an ‘urgent’ notifiable condition. It must be notified by medical practitioners and pathology services immediately to the Department of Health by telephone on 1300 651 170 (24/7) upon initial diagnosis (presumptive or confirmed). Pathology services must follow up with written notification within 5 days. For more information, see Notifiable infectious diseases, conditions and micro-organisms.

This is a Victorian statutory requirement.

Primary school and children’s services exclusion for poliomyelitis

Exclude for at least 14 days from onset; readmit after receiving medical certificate of recovery. Contacts are not excluded.

For more information, see the School exclusion table for primary schools and children's services.

Infectious agent of poliomyelitis

Poliovirus is an enterovirus and a member of the Picornaviridae family; types 1, 2 and 3 cause disease. Both wild type 2 and 3 have been declared eradicated by the World Health Organization. Only type 1 wild poliovirus remains.

Identification of poliomyelitis

Clinical features

The majority of polio infections are either asymptomatic or present as a non-specific febrile illness. Flaccid paralysis occurs in less than 1 per cent of poliovirus infections.

Symptoms of minor illness include fever, malaise, headache, nausea and vomiting. If the disease progresses to major illness, severe muscle pain and stiffness of the neck and back with flaccid paralysis may occur.

The most characteristic feature of polio paralysis is its asymmetric distribution, which affects some muscle groups while sparing others. Fever and muscle pain are generally present at onset, and the maximum extent of paralysis is usually reached within 3–4 days. Progression of paralysis almost invariably halts when the patient becomes afebrile. The site of paralysis depends upon the location of nerve cell destruction in the spinal cord or brain stem. Proximal muscles of the extremities tend to be more involved than distal. The legs are more often affected than the arms.

If the virus spreads to the nervous system, it can cause major illness, such as encephalitis, meningitis and paralysis. In severe cases, paralysis of the respiratory and swallowing muscles can occur and is life-threatening. After 60 days, the existing degree of paralysis is likely to be permanent.

Sensory loss is very rare, and its occurrence should strongly suggest some other diagnosis, such as Guillain-Barré syndrome.

Post-polio syndrome is an infrequent recurrence of muscle weakness that may occur many years after initial infection. It is thought to be due to progressive dysfunction and loss of motor neurons that compensated for the neurons lost during the original infection, rather than to persistent or reactivated poliovirus infection.

Vaccine-associated paralytic poliomyelitis (VAPP) is a very rare complication in recipients of oral polio vaccine (which has attained neurovirulence) or in their contacts. Approximately one case occurs per 2.9 million doses of vaccine. The risk is greater for the first dose than subsequent doses and is slightly greater for adults than for children. The clinical features of vaccine-associated paralytic polio are similar to those caused by wild-type polio.

Circulating vaccine-derived polioviruses (cVDPVs) can also occur. The oral vaccine strain regains neurovirulence through person-to-person transmission; this has caused outbreaks in regions where oral polio vaccine is still in use. The oral polio vaccine has not been used in Australia since 2005.

Diagnosis

A clinical history, including the vaccination status of the case and household contacts and any recent travel, is important.

A clinical diagnosis can be confirmed by virus isolation or detection by nucleic acid testing. Specimen samples include:

• Faeces (preferred specimen) – collect 2 samples more than 24 hours apart within 14 days of illness onset
• Throat swab or nasopharyngeal aspirate
• Cerebrospinal fluid (CSF) - CSF usually reveals a mild elevation in protein and a lymphocytosis.

The department requires that all suspected cases of polio have appropriate faecal specimens sent for analysis by the National Enterovirus Reference Laboratory (NERL), managed by the Victorian Infectious Diseases Reference Laboratory. The NERL can differentiate between ‘wild-type’ and vaccine-associated strains.

The department coordinates with clinicians and the NERL to ensure that appropriate infection control procedures are followed in the collection, transfer and analysis of all clinical specimens from patients with suspected polio.

Incubation period of poliovirus

The incubation period is between 3 and 35 days; for paralytic cases, it is 7–21 days.

Reservoir for poliovirus

Humans.

Mode of transmission of poliovirus

Wild poliovirus is spread through faeces and saliva. It is primarily transmitted through faecal–oral spread and is an important consideration where sanitation is poor. Ingestion of poliovirus can occur through person to person contact or consumption of contaminated food and water.

'Live' oral polio vaccine (OPV) virus can be shed in the faeces for 6 weeks and may lead to infection in unvaccinated contacts. Unvaccinated household contacts of a case should be vaccinated at the same time. Stressing the importance of handwashing for parents following nappy changing and disposal is important.

Period of communicability of poliomyelitis

The risk of transmission of infection is greatest for the 7–10 days before and after the onset of symptoms.

The virus persists in the pharynx for approximately 1 week and in the faeces for up to 6 weeks, or longer (potentially years) in the immunosuppressed.

Transmission of the virus is possible for as long as the virus is excreted.

Susceptibility and resistance to poliomyelitis

Anyone who is not immune (vaccinated) is susceptible to infection and can spread polio to others.

Australia is currently free of polio, but the risk of importation into Australia remains. Non-immune people may become infected in countries where polio is still circulating.

Natural infection provides lifelong immunity, but only to the specific type that caused the infection. Reinfection is rare but can occur if the person is infected with poliovirus of a different type.

IPV gives protection against all three types of poliovirus. The 3 dose primary course of polio vaccine is at least 99 per cent effective against the disease.

Public health significance and occurrence of poliomyelitis

Before vaccination programs, polio occurred worldwide. Since the Global Polio Eradication Initiative was launched in 1988, the following WHO regions have been certified polio-free: the Americas in 1994, the Western Pacific (of which Australia is a member) in 2000, Europe in 2002, South-East Asia in 2014 and Africa in 2020. Since 1987, there has been one case of wild poliovirus reported in Australia, in 2007. This case was in an overseas-born person, who acquired the disease during a visit to Pakistan.

Afghanistan and Pakistan remain the only countries with endemic transmission of wild-type poliovirus. In these regions, cases of polio occur both sporadically and in epidemics.

Circulating vaccine-derived poliovirus from the oral polio vaccine is rare, particularly since the removal of the poliovirus type 2 component of the vaccine in 2015. However, outbreaks with vaccine-derived strains can still occur in populations with significantly low immunisation rates or in people with primary immunodeficiency and long-term excretion.

Over the past 5 years, outbreaks have been reported in countries including the Philippines, Indonesia and Papua New Guinea.

In countries where polio has been eradicated, wild poliovirus from endemic countries can still be imported, therefore vaccination must continue until polio is eradicated worldwide.

Polio remains a predominantly childhood illness; 80 per cent to 90 per cent of cases occur in children less than 5 years old, although outbreaks affecting young adults have occurred.

Control measures for poliomyelitis

Preventive measures

Universal vaccination in early childhood is the most effective means of preventing and eradicating poliomyelitis. Catch-up immunisation is recommended for unimmunised or partially immunised children and adults.

Immunisation is also recommended every 10 years for adults at higher risk of exposure to polio, such as those travelling overseas, healthcare workers in possible contact with polio cases and laboratory workers who may have contact with poliovirus. See Australian Immunisation Handbook.

OPV is no longer used in Australia. OPV and IPV vaccine are interchangeable. Children who started their polio vaccination schedule with OPV should finish it with IPV vaccine or an IPV-containing vaccine.

Protection against polio is available free of charge under the National Immunisation Program Schedule:

• infants at two, four and six months – immunisation in the form of a diphtheria, tetanus, whooping cough, hepatitis B, polio and Haemophilus influenzae type b (Hib) vaccine (six-in-one vaccine)
• children at four years – a booster dose in the form of a diphtheria, tetanus, whooping cough, polio vaccine (four-in-one vaccine)
• eligible young people to 20 years of age who missed childhood immunisation
• refugees and other humanitarian entrants of any age if they did not receive the vaccines in childhood and it is recommended to receive the vaccine.

In Victoria, immunisation against polio is also free for certain people who missed vaccination during their period of eligibility. Refer to Victorian Immunisation Schedule.

Both IPV and OPV give mucosal and humoral protection. While IPV results in lower levels of intestinal immunity compared to OPV, it remains highly effective in preventing polio. Many industrialised countries have now changed to IPV alone for routine immunisations due to the successful eradication of polio in these regions and concerns about VAPP and cVDPV.

OPV is still used in many developing countries because of the higher risk of exposure to wild poliovirus, the low cost of the vaccine, the ease of its administration and its excellent capacity to provide population-level immunity. Polio eradication will ultimately require the synchronised cessation of OPV in order to prevent vaccine-derived cases. As demonstrated through the global coordination of bivalent OPV replacing trivalent OPV in 2016, following the eradication of type 2 wild poliovirus in 1999.

In addition to vaccination, poliovirus infections can be reduced by practising good hygiene and eating and drinking safely, when travelling to areas where polio is known to circulate. Clinicians should encourage travellers to:

• Wash their hands with soap and hot running water before handling food, after going to the toilet or having contact with nappies or use hand sanitiser fi clean handwashing facilities are not available.
• Only drink and prepare food with clean water.
• Avoid coming into direct contact with sewage.

Control of case

There is no specific treatment for poliovirus. Symptomatic cases require expert supervision and may need ventilation support. Early physiotherapy may increase the level of function and reduce the risk of physical deformities as a result of paralytic polio.

Contact precautions should be initiated in hospital settings, additional precautions maybe required based on risk assessment, completed by the health services infection control team. Cases should be managed in a single room with ensuite facilities. In communities with appropriate modern sewerage systems, faeces and urine from infected patients can be disposed of directly into sewers without preliminary disinfection. Terminal disinfection is required for all other potentially contaminated items.

For all cases, isolate in hospital or at home and use contact precautions. Isolation should continue until two stool samples taken 7 days apart are shown to be negative for poliovirus. Children must be excluded from primary schools and children’s services for at least 14 days from onset. They may return only after receiving a medical certificate of recovery.

Control of contacts

Vaccination of household and other close contacts (for example, people who have shared a toilet with the case, healthcare workers, food handler contacts and children and staff in childcare) is recommended but may not contribute to immediate control because susceptible contacts are often infected by the time the first case is recognised. Household contacts require home quarantine until two negative stool specimens taken 24–48 hours apart have been collected.

Active case finding, especially among children, ensures the early detection of related cases and facilitates control.

Control of environment

In communities with modern sewerage systems, faeces and urine can be disposed of directly into the system without preliminary disinfection.

Once the poliovirus is shed, it can survive outside the human body for weeks at room temperature. Therefore, proper cleaning and disinfection of areas contacted by an infected individual are required to prevent onward transmission. This must occur in toilets that the case has used while infectious, which may include toilets in the case’s home, doctor’s surgery, airplanes and airports. Effective disinfectants are those that contain free chlorine, such as sodium hypochlorite, bleach, glutaraldehyde solutions, formaldehyde solutions and iodophors.

Reinforce good personal hygiene practices and suggest a clean-up of kitchen and bathroom surfaces and fixtures used by the case during their infectious period, using a chlorine-based solution, to prevent the spread of viruses to others. Cases should refrain from preparing food for others while symptomatic.

Outbreak measures for poliomyelitis

In countries such as Australia where polio has been eradicated, a single case of wild-type polio is considered a public health emergency. The department must be notified immediately of all suspected or confirmed polio cases. At the national level, the Poliomyelitis Detection Outbreak Response Plan for Australia would be activated.

The department, alongside Local Public Health Units investigate all suspected and confirmed cases to:

• determine whether the patient’s disease is caused by an imported wild virus, an imported vaccine-derived poliovirus or a poliovirus acquired from a laboratory
• determine whether the patient’s disease is a VAPP case and, if it is believed to be a VAPP case, obtain details of vaccine history, batch number, virus type, severity and persistence of residual paralysis 60 days after onset
• implement appropriate case and contact control measures