Enterovirus D68 and Paralysis

An increasing number of reports have surfaced regarding ‘polio-like’ symptoms in children, leading doctors to investigate a connection with enterovirus D68[i]. Enterovirus D68, a rare and predominantly respiratory virus, belongs to a larger group of Enteroviruses. This genus of viruses is among the most common source of viral infections in the world. They are responsible for infecting up to 15 million Americans per year. However, most infected have no symptoms. Of those who do become symptomatic, the vast majority experience mild illness, similar to that of the ‘common cold’[ii]. 

Then, is there cause for concern?

Enterovirus D68 infection with severe respiratory complications/symptoms is very rare, generally occurring in children with compromised immune systems, asthma or respiratory conditions. Paralysis in cases of enterovirus D68 is even rarer. As the number of cases increase, the number of patients with rare symptoms will also increase – as we are seeing here with such a widespread swath of infection. As of October 2^nd there were 514 confirmed cases spread across 43 states[iii].

Why is it causing paralysis?

Many viral infections can, in rare cases, infiltrate and damage the spinal cord and central nervous system: i.e. West Nile Virus, Echoviruses, and Adenoviruses. The most commonly associated virus with acute paralysis is Poliovirus. The genus Enterovirus actually contains both enterovirus D68 and the three types of Poliovirus. However, it should be known that paralysis associated with enterovirus D68 has been almost unseen, until now.

According to a CDC MMWR enterovirus summary report, the first case of enterovirus D68 entering the central nervous system was reported in 2005[iv]. This patient presented with acute flaccid paralysis. Before the outbreak became more widespread, there were cases of enterovirus D68 linked to acute flaccid paralysis in California between August 2012 and July 2013[v].

It is uncertain if paralysis-linked to enterovirus D68 is as rare and only-recently seen as described. The complicating factor is that (non-polio) acute-flaccid paralysis is not a nationally notifiable disease[vi]. Because of this, we do not have ‘baseline’ numbers for paralysis in the either the greater population or in children. Cases continue to be investigated at the practitioner level, but the data is not aggregated at the national level like some of the other notifiable diseases.

What is the prognosis for patients?

It remains unclear if the children suffering from paralysis in this outbreak will regain their muscle control. Some of the patients in Colorado have recovered and been released from the hospital, reportedly those with milder paralytic symptoms[vii].