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.
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.
There is currently an increase in the number of children in the US diagnosed with acute flaccid myelitis (AFM). This condition involves weakness of the arms and legs and may include other symptoms such as inability to breathe. The CDC has a complete definition of AFM at their website.
Cases of AFM in the US and Europe began to increase in 2014. The reason for this increase is not known. It has been suggested that enterovirus D-68 was responsible for the increased AFM observed in 2014 and 2016. This conclusion is based upon detection of EV-D68 genetic material (RNA) in the respiratory tract of children with AFM.
So far in 2018 there have been 72 confirmed cases of AFM in the US out of 191 suspected in 24 states. CDC indicates that the cause of most of these cases is unknown. Certain state health departments, such as New York and Colorado, are reporting detection of EV-D68 RNA from the respiratory tract of some children with AFM.
A second enterovirus, EV-A71, has been isolated from some of the AFM children in Colorado. This virus is different from EV-D68 and infects the intestine rather than the respiratory tract. EV-A71 causes a rash called hand, foot, and mouth disease. It is known to be shed in feces, is present in the blood (viremia) and may cause neurological disease. In contrast, EV-D68 is not found in the blood or feces. EV-D68 is very unstable in the acidic environment of the stomach and should not be found in the feces. EV-A71, like poliovirus, is stable in the stomach and can be passed in the feces where it is spread to others.
Currently news sources are reporting that some doctors claim that EV-D68 is causing the outbreak of AFM in the US. Some doctors are testing for the presence of the virus in the feces, which is incorrect because, as stated above, the virus cannot pass through the stomach without being destroyed.
EV-D68 is unusual in its apparent ability to move from the respiratory tract to the nervous system. Our laboratory is interested in understanding this mode of virus spread. One way that we are studying the virus is by using three-dimensional lung and brain cultures produced from induced stem cells.