The threat is also insidious. Non-polio enteroviruses, such as EV-D68, are thought to be very common, with most infections causing no symptoms or only mild symptoms initially, warns the Centers for Disease Control and Prevention (CDC).

Sleepwalking into disaster

Concerned about the lack of valid data on the burden of non-polio enteroviruses, Professor Thea Kølsen Fischer of the University of Copenhagen and her colleagues across Europe set up a network to understand the burden of enteroviruses causing severe disease including polio-like paralysis.

The ENPEN network have been investigating the circulation of paralytic enteroviruses in Europe including enterovirus D68 and enterovirus A71, and documented the circulation of these “poliovirus cousins” in all countries where they have looked.

Their investigations suggest genetic changes in the EVD68 virus is likely one of the explanations to the increased virulence and increased presence of this virus during the past decade.

In a recent study from the UK using biobanked blood samples from two decades, Dr Heli Harvala (University College London, UK) who is also a cofounder of the ENPEN network, documented how the seroprevalence of D68 is increasing over time in all age groups.

“Patients can enter hospital with severe respiratory symptoms, but a week after the respiratory symptoms have passed then sudden onset of paralysis can be seen and enterovirus D68 can end up as much more than just a cold,” explained Prof Fischer, although early in its progression the symptoms can be similar.

“Sadly in significant numbers of cases, these infections are progressing to serious complications including lasting paralysis. Yet we have this huge asymmetry in global health programmes, polio having strong surveillance and vaccination programmes. Yet non-polio enteroviruses have neither. Because we don’t have well developed surveillance in place, we can’t say for sure what proportion of these enterovirus infections are leading to serious complications.”

Within the poliovirus surveillance programmes, the clinical cases with central nervous system symptoms and the AFP cases can see non-polio enteroviruses detected, but analysis is usually incomplete and merely as a by-product as the enterovirus positive samples are usually not further tested into subtypes.