Poliomyelitis and Post Polio Syndrome

The Disease

Poliomyelitis, formerly known as infantile paralysis and colloquially as polio, is an infectious neurological disease caused by any of the three serotypes of poliovirus - Brunhilde (Type 1), Lansing (Type 2) and Leon (Type 3). The virus attacks the motor neurons and brainstem, resulting in varying degrees of muscle weakness and in severe cases, complete paralysis. The majority of individuals will experience a mild influenza type illness from which they will fully recover. However, an unfortunate few, about one in a hundred cases, will develop one of three forms of paralytic polio – spinal, bulbar and bulbar spinal - according to the area of the central nervous system which is affected and the extent of the damage. The after effects of polio can be lifelong and the disease is potentially fatal.

Occurrence

Western Australia’s earliest reported case of poliomyelitis occurred in 1879 when a two year old boy from the rural town of York died of the disease, then known as infantile paralysis. In the first half of the twentieth century sporadic cases, minor outbreaks and epidemics were seen in many countries round the world. Isolated cases occurred in Western Australia but in 1948, 1954 and 1956 a sharp increase in the number of diagnoses and the pattern of spread in which patients had had close contact resulted in the outbreaks being classed as epidemics. Between 1917 and 1972, 1715 cases of polio were recorded in WA, most frequently in children.

Transmission

Polio only occurs in humans and is passed between individuals who are in close association. Where sanitation is poor and hygienic practices inadequate, poliovirus is transmitted via the oral faecal route. The carrier excretes the virus in faeces and the new host is infected as a result of contact with the carrier or swallowing contaminated food or water. There is also some evidence to suggest that during an epidemic when case numbers are high, the virus can be transmitted in droplets of saliva or mucus during coughing, talking and sneezing.

The Epidemics

While sporadic cases of polio are concerning a more alarming characteristic of poliovirus is its ability to cause epidemic disease. The first epidemic was recorded in Sweden in 1887 and subsequently in other Scandinavian countries, USA, Canada, New Zealand and Australia. While high standards of sanitation and hygiene have often been associated with a decrease in the prevalence of infectious disease, in polio the reverse situation has been observed. The disease has become more prevalent as standards of living have risen.

One explanation is that before the late 19th century poliovirus was ubiquitous in the environment because of poor sanitation and hygiene. With faecal particles contaminating food and water supplies, infection occurred almost universally in early childhood. Paralytic disease occurred rarely and most children experienced a mild illness from which they fully recovered. It seems likely that the children developed a lifelong immunity to whichever type of poliovirus they had been exposed to.

As standards of living rose and sanitation and hygiene improved, significant numbers of adolescents and adults were never exposed to the poliovirus. Should it then be introduced into an unprotected and therefore susceptible community, the likelihood of an epidemic developing would be extremely high.

In Australia the first epidemic of polio struck Port Lincoln in South Australia in 1895. Dr CA Altmann reported 14 cases in a population of 1500 over a 2 month period. In 2 cases more than one member of a family was affected. Nine patient required extended treatment with electrotherapy, massage and small doses of strychnine. The doctor noted with concern that several extensive polio epidemics had been reported overseas but he had been unable to find another in which the number of cases per head of population was as great as in Port Lincoln. In the Swedish epidemic 1 in 4500 people were affected but in Port Lincoln 1 in 108 contracted the disease.

Within the next decade or so polio epidemics began to occur in NSW, Victoria and Queensland. In 1937 local health authorities became concerned the disease could spread across the country to Western Australia. Early in 1938 the incidence of polio cases rose sharply to 48 but as there appeared to be no connection between the cases, the outbreak was not classified as an epidemic. It seems likely that WA escaped that situation until 1948 when 311 cases were reported. Another epidemic occurred in 1954 when 436 cases were recorded and a third followed in 1956 and accounted for most of the 401 cases reported that year.

Treatment

When damage to the nervous system results in muscle cells being completely deprived of stimulation, their ability to function is lost. However, in the majority of cases some nerve function is retained and muscle strength may improve with physiotherapy and occupational therapy. Treatment may continue for months or years but even then, muscle strength may not be fully restored.

Protection

The administration of an effective vaccine has been shown to protect against polio. In Australia in 1956 an immunisation program was introduced using the Salk vaccine which was administered by intramuscular injection. In 1961 it was replaced by the orally administered Sabin vaccine. As a result of the vaccination program, the number of cases fell dramatically and Australia was declared polio free in 2000. Currently this disease is endemic only in Afghanistan and Pakistan.

Current Vaccination Recommendations

The Australian Immunisation Handbook recommends vaccination for the following groups:-

a. The routine vaccination of infants aged 2, 4 and 6 months and 4 years. Free of charge.

b. A booster for vulnerable individuals such as health care workers.

c. Non vaccinated adults

Vaccine Derived Poliomyelitis

In 2020 when most Australians were concerned about the escalating number of COVID 19 infections in Victoria and the implications for the rest of the country, contributors to the Medical Journal of Australia (MJA) posed a question that was far from the minds of most – do Australian doctors still need to be on alert for new outbreaks of poliomyelitis? And now, in 2023 is the same concern relevant?

In 2000 the Global Polio Eradication Initiative declared Australia free of all three wild polio serotypes and by 2019 declared the eradication of serotypes 2 and 3 across the world. Serotype 1 (WPV1) remains endemic in Pakistan and Afghanistan but more recently new outbreaks of variants of WPV1 and WPV2 have been reported in nations previously declared polio free. They include Australia’s near neighbours Malaysia, the Philippines and Papua New Guinea, countries from which thousands of people have sought to enter Australia in recent years.

When the Sabin oral vaccine (OPV) replaced the intramuscular Salk vaccine its easily managed storage and administration helped to markedly increase vaccination rates around the world. OPV contains an attenuated or weakened virus which replicates in the intestine, stimulating the development of antibodies and boosting immunity. But the attenuated virus is also excreted and where sanitation and immunisation levels are inadequate for the protection of the community, the excreted virus can be transferred to vulnerable individuals. In some cases it can mutate into a form known as vaccine derived poliovirus (VDPV) which can present as paralytic poliomyelitis.

In Australia health workers stopped administering OPV in 2005 but a VDPV carrier entering the country could potentially introduce the poliovirus to the small percentage of unimmunised people. Environmental surveillance which includes sewerage sampling is labour intensive and costly but clinical surveillance measures are in place. However some doctors have been unaware that they should report all presentations of the most common symptom of poliomyelitis - acute flaccid paralysis - and request further investigations which include analyses of stool samples to accurately diagnose the cause. The best means of protecting the population is to ensure that these procedures are followed and vaccination programs continue. In fact both these public health measures are essential if Australiais to remain polio free while some developing countries continue to work towards that goal.

As COVID 19 cases continue to occur in many parts of the world, poliomyelitis remains far from the minds of many Australian doctors. But since the article in MJA was written, the situation has changed. When the Federal Government closed the international borders Australians were protected from VDPV. Arrivals and departures that were permitted were strictly regulated. But now that the incidence of COVID 19 has subsided and travel restrictions abolished, the possibility of poliovirus being reintroduced will increase.

As recently as June 2022 poliovirus was detected in the Beckton sewers which service millions of people living in north and east London. As the oral vaccine has not been used in the United Kingdom since 2004 British scientists believe the virus originated from someone who had received OPV overseas. The health authorities regarded the discovery as a national incident and informed the World Health Organisation. In September the governor of New York USA declared a state of emergency when several cases of polio were notified. As with other serious infectious diseases, health care workers need to remain vigilant and at this stage no country can afford complacency.

Post-Polio Syndrome

Decades after the initial infection, many polio survivors develop a condition known as post- polio syndrome, sometimes referred to as late effects. Typically they experience progressive and persistent new muscle weakness which may be accompanied by fatigue, muscle atrophy and joint and muscle pain and a general deterioration in physical ability – and in some cases difficulty with breathing or swallowing. Patients are likely to benefit from the support and care provided by a multidisciplinary team of medical and allied health professionals as well as advice from the Post-Polio Network.

Surveillance

The World Health Organisation declared Australia polio-free in 2000 but poliovirus is still being detected in a number of countries around the world. The Australian Government Department of Health and Aged Care funds a surveillance program to contribute to the worldwide eradication of the disease. The Polio Infection Outbreak Response plan monitors the presence of the virus in Australia and overseas countries with the aim of detecting imported cases, mitigating the risk of local transmission and providing evidence that Australia is maintaining its polio free status.

Australia’s near neighbours in the Western Pacific are polio free but in 2023 poliomyelitis remains endemic in Pakistan and Afghanistan while vaccine derived polio has been detected in Indonesia, Israel, Britain, the United States of America and Sudan and 20 countries on the African continent.

Should a single case of poliomyelitis be detected in Australia, a public health emergency will be declared. State and territory health departments, advisory committees, organisations and clinicians will be responsible for initiating a rapid response.