Last year, the U.S. witnessed a curious outbreak of temporary paralysis among children, something the Centers for Disease Control and Prevention (CDC) struggled to explain. Suspicions were aroused that it may have a viral origin, and one particular strain received interest as a possible cause or contributing factor.
But it seems the situation has now become even more perplexing because a different, but related, virus has recently been isolated from one individual, leading scientists to believe that this newly discovered strain may also be to blame.
The situation began to unfold last summer when children across the U.S. were struck down with a condition called acute flaccid paralysis, a common sign of polio that’s characterized by the rapid onset of extreme muscle weakness and loss of muscle tone. Interestingly, the outbreak, which affected almost 120 children across 34 states, coincided with an outbreak of respiratory disease caused by a type of enterovirus – EV-D68 – which is related to the polioviruses.
Although correlation does not imply causation, the timing did suggest that there could be an association between the two. However, EV-D68 was only found in 20% of those tested, and this virus typically causes respiratory syndrome rather than systemic disease. While this still doesn’t rule out the possibility that this virus could have been involved, it does suggest that some other factor was also at play. And to confuse matters even more, one case has now been linked with a different type of enterovirus, C105, which belongs to the same enterovirus species that includes the polioviruses, Enterovirus C.
The patient was a 6-year-old girl from Virginia who was taken to the hospital last October for progressive weakness on her right side, which eventually resulted in a loss of reflexes for her biceps and triceps. Before examination, the child and her close family had been struck with a cold, which is commonly caused by a type of enterovirus called a rhinovirus. Although the patient recovered from the cold, she continued to experience pain in her right arm, her shoulder began to droop and she struggled to use her right hand.
Following admission, a sample of spinal fluid was taken for examination, which turned out to be negative for enterovirus, but subsequent testing of a nasal swab revealed that she was infected with enterovirus C105. That was a surprising find given the fact that this virus was only identified back in 2010, and those patients were from Peru and the Republic of Congo.
It seems that C105 belongs to a string of recently identified enterovirus C subspecies, but the majority of these have been associated with respiratory illness. The virus isolated in the Republic of Congo, however, was found in patients experiencing fatal acute flaccid paralysis.
The detection of C105 in the U.S. also indicates a worldwide presence, which could be problematic because these newly detected subspecies show great genetic variation in the region normally targeted by tests. This could therefore explain why 80% of the U.S. children involved in the outbreak of acute flaccid paralysis were negative for D68, as it’s possible they were infected with C105 instead, but it wasn’t picked up by conventional tests. However, the situation is still confused by the fact that none of the U.S. patients had enterovirus in their spinal fluid, which would be expected if the virus is causing the onset of neurological symptoms. In the absence of such evidence, the jury is still out as to whether enteroviruses are responsible for the outbreak.