Polio - The Late Effects Reality

INTRODUCTION: LATE EFFECTS OF POLIO (LEP) IN IRELAND

Medically, for many years, Polio was thought of as a static, non-progressive neurological disorder. This gave rise in many countries, including Ireland, to the thinking that it should not be defined as a long-term illness. Then in the 1970s

"reports began to surface that people who had recovered from paralytic Polio decades earlier were developing unexpected health problems such as excessive fatigue, pain in muscles and joints and most alarming of all, new muscle weakness" (Halstead, 1998).

So, in the 1980s, the terms Post Polio Syndrome (PPS) and Late Effects of Polio (LEP) came into use in the medical profession. (In the body of this report the abbreviation LEP will be used throughout.)

However, it turns out that it is not a new disorder at all, as Halstead (1998) states

"It was described in French Medical literature in 1875, and then, as often happens in medicine, it was forgotten; over the next 100 years approximately 35 reports on post Polio weakness were published in the medical literature".

Studies published by the Government of the State of Queensland, Australia (1998) suggest that the time period between the acute Polio and onset of LEP range from 8 to 71 years, the average interval being around 35 years.

Although all of these studies are recent, in research terms, they have all been superseded, at least in part, by one critical factor. All the derived figures have excluded persons with a history of non-paralytic Polio. Historically there has been a medical tendency to require a history of acute paralytic Polio before any diagnosis of LEP would be even considered. Papers that were written in the 1950s do not support this tendency. Salter (2000), in his paper Post Polio Population Statistics – A Review, reported "evidence of a level of neuronal damage by the Polio virus that does not present any clinical signs of paralysis at the time of infection". Include these in the above estimates and minima and maxima figures of 23,200 to 26,500 of Polio Survivors in the Irish population are derived.

Not all of these are expected to develop LEP. No one knows how many paralytic Polio Survivors have LEP, let alone the asymptomatic cases. Some studies suggest 40% of paralytic cases will develop LEP (Halstead, 1998); other studies have ranged from a low of 22.4% to a high of 60% (Government of the State of Queensland, 1998). Field (1995), in his United Kingdom based National Survey of Polio Survivors, states

"Between 20 – 40 years after their original infection by Polio approximately 77% of survivors experience new symptoms".

Therefore, if a mid-point is taken, say 40%, it suggests that the number of Irish paralytic Polio Survivors who will experience LEP ranges from 3,000 – 4,200.

Research into this condition is currently being undertaken in Ireland and internationally. This research is primarily clinically based, studying the physiological symptoms. At this stage, there is no known cure.