In August of last year, a seldom seen (at least, in North America) non-polio enterovirus D-68 (EV-D68) appeared in America’s Midwest and quickly spread across the nation, causing a wide spectrum of respiratory illness, predominantly in young children and adolescents (see Kansas City Outbreak Identified As HEV 68).
At roughly the same time, a coincident rise in cases of neurological illness with AFP (acute flaccid paralysis) or limb weakness – often associated with a recent respiratory illness – was reported across the country.
A month later the CDC issued a HAN: Acute Neurologic Illness with Focal Limb Weakness of Unknown Etiology in Children, alerting doctors around the country to be aware of this trend, and providing information on reporting cases. While primarily associated with respiratory symptoms, EV-D68 had previously been linked to neurological presentations, including a small cluster of cases the previous winter (see Acute Flaccid Paralysis Cases In California).
Although a causal link wasn’t established, due to the timing and the fact that other enteroviruses have been linked to neurological illnesses, there was a high degree of suspicion that the two conditions were linked.
Enteroviruses encompass a large family of small RNA viruses that include the three Polioviruses, along with myriad non-polio serotypes of Human Rhinovirus, Coxsackievirus, echovirus, and human, porcine, and simian enteroviruses. We’ve looked at EV-71 and the Coxsackieviruses on numerous occasions in regards to AFP (Acute Flaccid Paralysis) and HFMD (see here, here & here).
According to the CDC Non-Polio Enteroviruses (NPEVs) cause 10 to 15 million – mostly mild and often asymptomatic – infections in the United States each year, primarily among infants, children, and teenagers.
Fever, runny nose, sneezing, coughing, a skin rash or mouth blisters, and body and muscle aches are the most commonly reported symptoms.
First isolated in 1962, but only rarely reported in North America since, in 2011 – in MMWR: Clusters Of HEV68 Respiratory Infections 2008-2010 – we looked at a recent increase in EV-68 associated clusters reported in Asia, Europe, and the United States during 2008--2010.
We continued to watch the progress of this most recent outbreak over the winter (see CIDRAP: Likely That Polio-like Illness & EV-D68 Are Linked & Eurosurveillance: Acute Flaccid Paralysis Following EV-D68 Infection – France), and the most recent CDC NCIRD update on last year’s outbreak was posted in early March.
From August 2, 2014 to March 2, 2015, CDC has verified reports of 115 children in 34 states who developed acute flaccid myelitis that meets CDC’s case definition. CDC continues to collaborate with partners nationally to investigate reported cases, risk factors, and possible causes of this condition.
- The median age of the children was about 8 years.
- Almost all of them were hospitalized; some were put on breathing machines.
- Most patients had fever and/or respiratory illness before onset of neurologic symptoms.
- About two thirds of the children who have been observed (median 19 days) after their illness reported some improvement in symptoms, while about one third showed no improvement. Only two of the children have fully recovered.
This week a genetic analysis of this emerging enterovirus was published in The Lancet - A novel outbreak enterovirus D68 strain associated with acute flaccid myelitis cases in the USA (2012–14): a retrospective cohort study – that not only strengthened the link between the EV-D68 infection and paralytic complications, but also identified the virus as being part of a new clade (B1) with polio-like changes that emerged about 5 years ago.
Mar 31, 2015
A careful study of children at two Colorado and California hospitals who had polio-like illnesses strengthens the evidence that cases were related to enterovirus-D68, which caused a widespread outbreak of severe respiratory illnesses in US children last year, according to a report published today in The Lancet Infectious Diseases.
The virus was found in 12 of 25 patients who had the polio-like condition, called acute flaccid myelitis (AFM), and the proportion probably would have been higher if respiratory samples had been collected earlier, the researchers said. In addition, a thorough genomic search for other viruses in the neural fluid of 14 of the patients found no signs of any other virus that could have caused the patients' limb weakness and related problems.
"These findings strengthen the putative association between enterovirus D68 and acute flaccid myelitis and the contention that acute flaccid myelitis is a rare yet severe clinical manifestation of enterovirus D68 infection in susceptible hosts," the authors wrote.