From August 2014 to March 2015, the Centers for Disease Control and Prevention (CDC) verified reports of 115 children in 34 states who developed acute flaccid myelitis. Now a research team led by scientists from the University of California, San Francisco found the genetic signature of enterovirus D68 (EV-D68) in half of the California and Colorado children diagnosed with acute flaccid myelitis–findings that strengthen  the association between EV-D68 infection and acute flaccid myelitis, which developed in only a small fraction of those who got sick.

Numerous, spheroid-shaped Enterovirus-D68 (EV-D68) virions/Cynthia S. Goldsmith, Yiting Zhang
Numerous, spheroid-shaped Enterovirus-D68 (EV-D68) virions/Cynthia S. Goldsmith, Yiting Zhang

The research was published online in the journal, The Lancet Infectious Diseases.

Researchers analyzed the genetic sequences of EV-D68 in children with acute flaccid myelitis and discovered that they all corresponded to a new strain of the virus, designated strain B1, which emerged in 2010.

The B1 strain was the predominant circulating strain detected during the 2014 EV-D68 respiratory outbreak, that from mid-August 2014 to January 15, 2015, CDC or state public health laboratories confirmed a total of 1,153 people in 49 states and the District of Columbia.

The virus was detected in one child as his acute paralytic illness was worsening in both respiratory and blood samples for the first time. In addition, the study also included a pair of siblings, both of whom were infected with genetically identical EV-D68 virus, yet only one of whom developed acute flaccid myelitis.

“This suggests that it’s not only the virus, but also patients’ individual biology that determines what disease they may present with” said Charles Chiu, MD, PhD, an associate professor of Laboratory Medicine and director of UCSF-Abbott Viral Diagnostics and Discovery Center. “Given that none of the children have fully recovered, we urgently need to continue investigating this new strain of EV-D68 and its potential to cause acute flaccid myelitis.”

Among the 25 patients with acute flaccid myelitis in the study, 16 were from California and nine were from Colorado. Eleven were part of geographic clusters of children in Los Angeles and in Aurora, Colorado, who became symptomatic at the same time, and EV-D68 was detected in seven of these patients.

Although the researchers found EV-D68 in the children’s respiratory secretions and in the blood from one case, they did not find it in cerebrospinal fluid. The researchers said this may not be surprising given that other nerve-damaging viruses, like polio, are also extremely difficult to detect in cerebrospinal fluid.