The number of confirmed Enterovirus D68 cases sits at 691 people from 46 states, but due to the complex and lengthy testing process, there has been a huge backlog of samples awaiting testing. Anecdotal reports from around the nation suggest the actual number of infections is many times higher, but patients with mild or moderate symptoms rarely get tested.
Today the CDC has announced their development of a faster, more streamlined lab test, which should help clear up the backlog of untested samples.
This test is a is a “real-time” reverse transcription polymerase chain reaction, or rRT-PCR, and it reportedly identifies all currently circulating strains of EV-D68 in the United States. It should quadruple the CDC’s lab capacity to turn around test results.
But at the same time, a faster test could artificially make the outbreak appear to be accelerating, so the CDC is taking great pains to assure that any sudden jumps in the number of confirmed cases in the coming days is more likely to be due to processing this backlog, than from a sudden spike in transmission.
This from the CDC’s press release:
Confirmed cases will appear to rise as agency accelerates specimen testing; Changes in case counts due to faster testing will not represent a real-time influx of new cases
The Centers for Disease Control and Prevention (CDC) has developed and started using a new, faster lab test for detecting enterovirus D68 (EV-D68) in specimens from people in the United States with respiratory illness. This test will allow CDC to more rapidly test remaining specimens received from states since mid-September.
Every year, enteroviruses and rhinoviruses cause millions of respiratory illnesses in children. This year, EV-D68 has been the most common type of enterovirus identified, leading to increases in illnesses among children and affecting those with asthma most severely. Other rhinoviruses and enteroviruses continue to be detected as well.
CDC expects, as with other enteroviruses, that EV-D68 infections will likely begin to decline by late fall. The real-time lab results combined with data on hospital admissions will help us understand when and where the EV-D68 outbreak is ending. CDC has received informal reports from some hospitals and states who are seeing signs of decreasing EV-D68 infections. CDC is gathering more information from states and assessing whether this represents a national trend.
“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,” said Anne Schuchat, MD, assistant surgeon general and director of CDC’s National Center for Immunization and Respiratory Diseases. “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.”
Since the outbreak of EV-D68 began in August, CDC has tested 1163 specimens submitted by hospitals and from 45 states. Of the specimens tested by the CDC lab from August 1 to October 10, about half have tested positive for EV-D68. About one third have tested positive for a rhinovirus or an enterovirus other than EV-D68. The new lab test will allow us to process the approximately one-thousand remaining specimens at a much faster rate.
Testing for EV-D68 is not used to determine treatment for a particular patient. Treatment for patients with EV-D68 is supportive therapy, such as oxygen therapy. The outcome of the EV-D68 test is to collect surveillance data to help public health officials target our responses to the outbreak, not to determine the treatment plan for a specific patient. CDC prioritized testing for the most severe cases since the outbreak began in August to get a better understanding of the disease.