Polio, or poliomyelitis, has almost been relegated to the annals of history by modern medicine and targeted vaccination programs. Two of the three strains of the virus that causes polio have now been eradicated worldwide, and efforts continue to try and finally eliminate this virulent disease.

What is Poliomyelitis?

Polio is a condition caused by the poliovirus. It can cause extensive damage to nerves, occasionally resulting in paralysis and serious morbidity. Only around a quarter of the people who are exposed to the virus develop the symptoms of the disease, and most of those people only experience flu-like symptoms and recover well. For a small proportion of people, however, it can be extremely serious and debilitating.

The most effective way for polio to be passed on is through contact with an infected person’s feces or saliva, reinforcing the importance of effective handwashing. People are most infectious for up to ten days before and after their first symptoms, but can continue to be contagious for several weeks afterwards. The virus thrives and multiplies in the human digestive system, and from there can begin to affect other parts of the body. The most profound symptoms occur when the virus begins to affect the central nervous system. 

There is no cure for polio, but symptoms can usually be well managed for the majority of infected people. 

Signs and Symptoms

The majority of people infected with the poliovirus do not go on to develop symptoms. They are, however, still able to pass it on even when asymptomatic, so poliovirus can spread through a community quickly.

Most people who do develop symptoms due to a poliovirus infection report a flu-like illness, with:

  • Nausea and vomiting
  • Headaches
  • Fever
  • A sore throat
  • General muscle aches

Less than 1% of people infected with poliovirus develop a more serious form of polio in which the virus enters the central nervous system and begins to damage nerves. This can cause paralysis, often of one or both legs. The paralysis in poliomyelitis may resolve within weeks or months, or can last a lifetime. People with continued paralysis from polio can completely lose sensation and control over the affected part – often a leg or an arm – resulting in muscle wastage. This can have a significant effect on people’s mobility and increase their risk of complications arising from mobility problems. The nerve damage and muscle wastage in polio can sometimes result in the characteristic ‘twisted’ leg associated with the condition.

Polio can sometimes affect the nerves and muscles which control breathing, and so respiratory complications are a leading cause of death in people with severe paralytic polio. 

A few people who have recovered from polio may continue to have symptoms, or polio sequelae, intermittently for many years – this is known as post-polio syndrome. Symptoms left over from the illness can worsen with no obvious triggers, or symptoms can recur. Muscle weakness, wastage and pain, and extreme fatigue can last a lifetime for someone with a history of poliomyelitis.

Polio Through History

Polio has been around for a long time and appears to have been well known among ancient civilizations; drawings and texts from as far back as 1500 BCE in Ancient Egypt show likely evidence of the effects of polio. 

Various terms have been used throughout history to describe illnesses now thought to have been polio – ‘infantile paralysis’, ‘tephromyelitis’, and ‘paralysis of the lower extremities’ are all descriptions of what would now be polio diagnoses, long before the virus was identified that linked the conditions together. The Scottish poet and novelist Walter Scott was famously affected by a childhood disease now retrospectively diagnosed as polio which left him paralyzed in one leg. He wrote candidly on the ‘singular’ types of treatment he underwent for this in the late 1700s.

Although polio has been affecting people since at least as far back as recorded history, it had a particularly serious impact in the late 19th and early to mid 20th century, and epidemics were reported across Europe and North America with increasing scope and severity. It is thought that, as public hygiene became the norm, people were more likely to avoid polio in childhood. Less exposure meant reduced immunity to a virus that remained present, and so when people did become infected by the virus it could spread through groups of people much more acutely than in times of greater passive exposure.

As an infectious disease that seemed to increasingly target wealthier nations and cause lifelong disability from childhood, polio became the most feared and studied condition of the time. Copious resources were directed to treating the polio epidemics; the nascent disciplines we would recognise as modern physiotherapy and occupational therapy services developed, along with various walking frames, callipers, and aids to support people affected. Infectious disease hospitals and wards were designed to try and contain the infection. The first ‘iron lung’ was developed by 1928, an early form of mechanical ventilation for those people whose polio had affected their ability to breathe. Black-and-white photographs remain of huge rooms containing twenty or thirty children each in individual coffin-sized metal boxes, each breath forced in and out by alternating pressures within the sealed apparatus. A picture of a medical zeitgeist within living memory, and a shocking reminder of how far we’ve come.

Alongside the treatment and management of polio symptoms, developments were being made in the field of prevention. An injectable polio vaccine became available in the US in the late 1950s which conferred swift and effective protection. As development continued, vaccines became more accessible, and both injected and oral vaccines are now used worldwide.

The Future of Polio

There are three known strains of the poliovirus; poliovirus 1, 2, and 3. Thanks to the efforts of a concerted vaccination campaign, poliovirus 2 and 3 seem now to be completely eradicated, making them, respectively, the second and third human pathogens to be completely eliminated (the first being smallpox). Polio 1 is still active, though currently in only three countries in the world; Pakistan, Afghanistan, and Nigeria. While Polio still exists anywhere, it has the potential to spread. Effective vaccination is essential to prevent widespread recurrence of this potentially deadly virus.