After its global emergence in 2014, subsequent outbreaks of enterovirus D68 occurred in 2016 and 2018. The expected outbreak of 2020 never materialized, likely due to masking and physical distancing put in place for the SARS-CoV-2 pandemic. As these measures are relaxed in multiple countries, increased in cases of respiratory virus infection have been observed, including enterovirus D68 in Europe.
A total of laboratory-confirmed 139 EV-D68 cases were identified between 31 July and 14 October 2021 in eight countries. The peak incidence was in September, in line with seasonal occurrence of enterovirus infections. Most of the cases were in males (88/139; 63%) and mainly younger than 5 years of age (120/139; 86%), with a median age of 3 years. Clinical symptoms were reported for 120 cases; most exhibited respiratory symptoms. While neurological symptoms were present in five cases, none was diagnosed with AFP or acute flaccid myelitis (AFM).
The re-emergence of EV-D68 in Europe serves as a reminder that surveillance for this virus must continue. So far there have not been reported cases of EV-D68 infections in the United States or in other countries outside of Europe. With increased relaxation of distancing and masking measures, it is only a matter of time before EV-D68 infections and associated AFM return.
The Centers for Disease Control and Prevention has published ‘Surveillance for Acute Flaccid Myelitis – United States, 2018’ in Morbidity and Mortality Weekly Report (click for link to article). The article summarizes AFM for 2014-2018.
There were 233 confirmed cases of AFM in 2018, which is the largest number since surveillance for this condition began in 2014. AFM is defined as a disease of the nervous system – the brain and spinal cord – in which muscles and reflexes become weak, often accompanied by paralysis. Recently the definition has been modified to include MRI evidence of spinal lesions. The number of AFM cases have increased since 2014, mainly in young children. However, AFM is a rare disease, affecting 1-2 per million children each year.
AFM is often called a ‘polio-like’ disease due to the paralysis that is observed in children with the disease. However, poliovirus is not found in the stool of children with AFM.
AFM was first defined in 2014 after reports of limb weakness in children across the US during an outbreak of respiratory disease caused by enterovirus D-68. AFM may also be associated with infections caused by other viruses, such as enterovirus A71, Coxsackievirus A16, West Nile virus and adenovirus. Since 2014 AFM surveillance has been conducted across the US.
Of the 233 patients with confirmed AFM in 2018, EV-D68 was the most frequently detected virus, mainly in respiratory samples. Only two samples of cerebrospinal fluid were positive: one for EV-D68 and one for EV-A71.
While it seems likely that EV-D68 is an etiological agent of AFM, additional proof is clearly needed. Such proof would include showing that EV-D68 causes similar clinical disease in animal models following respiratory infection. These experiments have not been done but are a focus of our research.
As of this date in 2018, CDC reports 116 confirmed cases of AFM in 31 states. These 116 confirmed cases are among the total of 286 reports that CDC is investigating.
This map illustrates the number of confirmed cases of AFM in each state, demonstrating the nationwide nature of this outbreak:
This graph displays the number of confirmed cases of AFM in the US:
CDC has established an AFM task force to encourage collaborations between CDC and the scientific community so that we can better understand the cause of AFM, how to prevent it, and how to treat it. More information on the task force can be found at this link. The first meeting of the task force will be on 4 December in Atlanta, GA.
Our laboratory has joined the AFM Consortium to bring together clinicians and basic scientists working on AFM.