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CDC reports faster lab test for detecting enterovirus D68
The CDC has developed and begun using a new, faster lab test for detecting enterovirus D68 in specimens from US patients with respiratory illness, according to a press release.
“CDC has received substantially more specimens for enterovirus lab testing than usual this year, due to the large outbreak of EV-D68 and related hospitalizations,” Anne Schuchat, MD, assistant surgeon general and director of CDC’s National Center for Immunization and Respiratory Diseases, said in the release. “When rare or uncommon viruses suddenly begin causing severe illness, CDC works quickly to develop diagnostic tests to enhance our response and investigations. This new lab test will reduce what would normally take several weeks to get results to a few days.”
Anne Schuchat
This year, EV-D68 has been the most common type of enterovirus identified, with an increase in illness among children, particularly those with asthma, the CDC reported.
The new test allows the CDC to more rapidly test the remaining specimens received since mid-September, according to the release. As is similar to other enteroviruses, EV-D68 infections are expected to begin declining by late fall.
The new lab test is a “real time” reverse transcription polymerase chain reaction that identifies all strains of EV-D68 that have been seen during the summer and fall, the release stated. There are fewer and shorter steps than in the prior test being used to identify EV-D68, and the new test allows more specimens to be tested at the same time.
The previous test had been in use by the CDC for about 9 years. Although it was very sensitive and could identify almost all enteroviruses, it was labor intensive and could not be “easily scaled up” to support the testing of large numbers of specimens seen in the current EV-D68 outbreak, according to the release.
The CDC has tested 1,163 specimens submitted by hospitals and 45 states since the EV-D68 outbreak began in August, with about half testing positive from Aug. 1 to Oct. 10, the release reported. Approximately one-third of specimens have tested positive for rhinovirus or a different enterovirus.
“The new lab test will allow us to process the approximately 1,000 remaining specimens at a much faster rate,” the CDC reported.
The real-time lab results combined with hospital admissions data are expected to help the CDC understand when and where the outbreak is ending. Hospitals and states have given informal reports to the CDC that indicate signs of decreasing EV-D68 infections, the release stated. To assess the situation, the CDC is gathering additional information from the states.
The number of confirmed EV-D68 cases is expected to increase substantially in the upcoming days as the CDC tests the remaining specimens it has received since mid-September, according to the release.
“These increases will not reflect changes in real time or mean that the situation is getting worse,” the release stated.
The new lab test will allow for testing up to 180 specimens per day, up from the previous 40 specimens per day, with testing expected to be completed on the samples received since mid-September within 7 to 10 days, according to the CDC.
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Enterovirus D68 has reemerged as a cause of respiratory tract infection and perhaps neurological disease in infants and young children. There are data that the virus has circulated in the past in the United States and elsewhere. The association with neurological disease, specifically a polio-like illness, including limb weakness and paralysis, is concerning; though the causative role of the virus in these diseases has not yet been established.
Clearly, expanding testing and surveillance is required to further define the epidemiology of the virus and to address the issue of disease presentations. The increased capacity of testing now offered by the CDC is a welcome development in this regard. However, detection of the virus would still require shipments of specimens to the CDC and the volume of specimens that can be tested may not be ideal to define local epidemiological trends. Here, diagnostics testing at specific hospitals in defined regions may improve the accuracy of the surveillance. Lastly, this type of testing (real time reverse transcriptase PCR) and other modalities such as serological assays in combination with rigorous epidemiological investigations will be needed to define the role of the virus in neurological disease.
Perspective
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Enterovirus D68 certainly surprised us this summer. First as a cause of primarily respiratory illness including wheezing and second with how widespread cases turned out to be. The additional diagnostic testing developed by CDC will allow us to define the spectrum of illness caused by this previously rare enterovirus. The increased capacity for EV-D68 testing probably won’t have a large impact on individual practices since most testing is being done on hospitalized patients. Since there is no specific treatment for EV-D68 a rapid diagnosis is not crucial for caring for clinic patients with this infection. It will be more important for physicians to diagnose the other common and treatable causes of respiratory tract disease such as influenza, pertussis, and bacterial pneumonia. EV68 testing will be important for cases of neurologic disease including flaccid paralysis that seems to have increased coincident with the EV-D68 respiratory outbreak. If EV-D68 continues to circulate in large numbers next year the EV-D68 PCR testing will likely be incorporated into the existing respiratory virus PCR panels now offered by many laboratories.