of the nineteenth century, when the first epidemics began in the cooler climates of industrialised Europe and the United States!
Such has been the dramatic success of vaccination programmes, using live attenuated viral vaccines taken by mouth, that polio has been largely eliminated from developed countries. In 2018, according to the Global Polio Eradication Initiative, the disease is now endemic in just three countries: Afghanistan, Nigeria and Pakistan. But, given the ease and extent of modern travel, we cannot rest assured until this historic and maiming disease is completely eradicated in these remaining pockets of potential contagion.
While poliomyelitis is now approaching global control, it is not the only enterovirus to afflict humanity. Other members of this virus family are still commonly encountered in developed countries, including viruses that can be baffling in their presentations and clinically unpredictable in the course of their illnesses. Perhaps the best known of these are the Coxsackie B viruses, which sometimes present with a condition known to doctors as epidemic pleurodynia. Also known as ‘Bornholm disease’, after the Danish island where it was first recognised, this can present as severe chest pain arising from inflammation in the intercostal muscles of the chest wall. Popularly known as ‘the devil’s grip’, the sudden onset and severity of the pain can mimic a heart attack. Coxsackie B viruses can occasionally cause inflammation of the brain, presenting as the condition known as myalgic encephalomyelitis, or ‘Royal Free disease’, named after the London teaching hospital where it first presented. The same enterovirus may also present with inflammation of the heart muscle, or myocarditis, coupled with inflammation of the membrane surrounding the heart, known as pericarditis, a combination that presents in both children and adults and can very occasionally prove fatal. Other enteroviruses, including the echoviruses and types 70 and 71 enteroviruses, can cause chest infections and various patterns of muscle, meningeal and brain infections, where the diagnosis of the causative virus may be exceedingly difficult to pin down.
Viruses and their associated illnesses can be very puzzling. Ever since we first discovered their enigmatic presence among us, questions have inevitably arisen as to the evolutionary purpose behind their behaviours. When faced with the unpleasant, sometimes life-threatening, effects of virus infections, we are inclined to wonder what possible benefit such behaviour might confer on the virus. In the case of the poliovirus we saw how it appears to be mere happenstance that the virus causes serious illness in a tiny minority of those it infects. But there are other viruses that sweep through the human population and inflict dreadful patterns of illnesses in the majority of those infected, sometimes accompanied by a high mortality. This is all the more baffling since all that matters to the virus is its survival and successful replication. Survival of the virus must surely be threatened by killing its host. When one views the same question from a medical perspective, we are inclined to question: why are some viruses so deadly?
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