Vernon had developed marked muscle weakness in his left leg. Sami, my Nigerian-trained registrar, came to discuss the case with me. The pattern suggested a peripheral nerve injury, but a slipped disc or a spinal tumour could also have been in the frame. At the end of the discussion, Sami gave a wry smile and commented, “Of course, in my country, I would also be thinking about polio.”
I have never seen polio – the last UK case occurred in 1984, the year before I started medical school. Many people are asymptomatic; others will suffer a flu-like illness for a week. In a minority, however, the virus gets into the nervous system and causes varying degrees of paralysis and sometimes death.
Ancient Egyptian artefacts depicting characteristic disabilities suggest that polio has been around for millennia, but major epidemics first emerged in the Victorian era. This is usually attributed to the population density in post-Industrial Revolution cities, but it is also possible that the virus acquired mutations that enhanced its infectivity. By the first half of the 20th century, polio had become one of the most feared diseases in Europe and the US. Outbreaks in the UK would affect thousands of people annually, many of them young children. Around 10 per cent of hospitalised cases would die, with permanent paralysis in many who survived.
Immunisation is the reason I’ve never seen a case. First developed in the early 1950s, successive vaccines helped eradicate polio in the Western world. Inspired by these successes, the World Health Organisation (WHO) launched the Global Polio Eradication Initiative in 1988. An extraordinary and sustained campaign has led to two of the three wild strains being finally eradicated within the past six years, and the remaining type 1 poliovirus is now found only in Pakistan and Afghanistan.
Nigeria was the final African country to clear the disease; it had a type 1 polio case as recently as 2016. The immunisation campaign there had foundered for a time because of misinformation rumouring that the vaccine was an American agent designed to render Muslim women infertile. The ongoing conflict being waged by Islamist militants has made parts of the country extremely dangerous for healthcare workers; in 2013 nine female vaccinators were killed in two separate shootings. But in 2020, with more than 95 per cent of the continent’s population immunised, Africa was finally declared polio-free.
The vaccines are not without their side effects. The oral version (OPV, which many readers will recall being given on a sugar lump) is a weakened live virus that, in rare instances, itself causes polio. The UK switched to injectable vaccine (IPV) in 2004 which, being inactivated, is incapable of causing disease. IPV is only suitable for maintaining protection once a country is polio-free. When trying to eradicate polio from endemic areas, OPV is more effective.
The world is now close to being rid of polio, the first such conquest since 1980, when smallpox was declared extinct as a result of a WHO-led vaccination campaign. Until polio has been fully eradicated, immunisation has to continue at high rates worldwide to prevent the virus re-emerging as a result of international travel. Thankfully, Vernon’s leg paralysis proved due to a simple nerve injury.
Covid has a far lower mortality rate than smallpox, or indeed malaria, the subject of another WHO initiative. But its high infectivity, capacity to overwhelm hospital services, and legacy of Long Covid make it a formidable problem comparable to polio. History tells us what will ultimately be needed: proper resourcing and global support for the Covax campaign being coordinated by the WHO. No nation will be able to return to full normality until all nations have been protected.
This article appears in the 05 May 2021 issue of the New Statesman, If not now, when?