Researchers at the Washington University School of Medicine in St. Louis have developed a new diagnostic test for enterovirus D68 (EV-D68), a virus that can cause severe respiratory illness. Previously developed tests for the virus take days to complete because the technique requires a lengthy process of sequencing sections of the viral genome and only labs at the Centers for Disease Control and Prevention (CDC) and a few state public health laboratories have the capability.
The new test involves an improved polymerase chain reaction (PCR) assay that might allow other laboratories to test for EV-D68 and reduce the time needed to detect the virus in the lab. Results on the new test were published in the August issue of The Journal of Clinical Microbiology and showed it to be very effective at identifying different strains of EV-D68.
Although EV-D68 is relatively rare, there have been outbreaks in the past. An outbreak last year resulted in over 1,000 cases and 14 deaths, according to the CDC. It caused serious illness in children in several states, sending many of them to hospitals.
EV-D68 has signs and symptoms similar to those of a cold or the flu and can be difficult to distinguish without testing. Confirming EV-D68 infection more quickly could help health practitioners make the right decisions about treatment. They could refrain from trying to treat EV-D68 with ineffective flu antiviral medications, for example, and be able to monitor the affected person more closely for serious symptoms such as trouble breathing or acute flaccid paralysis. Though typical care for EV-D68 is supportive, such as fluids and fever reducers, people with severe cases may require hospitalization and some have to be put on a ventilator to support their breathing.
Although last year's outbreak has ended, the new test remains an important tool in the event of future cases and outbreaks. Because the research was funded by the National Institutes of Health, the details of the test have now been fully published in the study and other labs can use the protocols to create their own tests for EV-D68.
"Commercial tests for respiratory viral infections typically don't distinguish between rhinoviruses, which cause the common cold, and enteroviruses, and within each of those groups there are many different types," said Gregory A Storch, MD, the senior author of the study and a professor of pediatrics. "Having a tool to identify which cases of respiratory illness are actually EV-D68 is an advantage for public health," says Storch. "These kinds of tests help treatment decisions because it is important to know that the patient doesn't have influenza or another disease that might require a specific treatment."
According to Dr. Storch, there are a number of variants of enterovirus D68 that are closely related genetically. However, slight variations in their genomes complicate researchers' ability to detect all variants with one test. The researchers isolated small pieces of viral DNA sequences that are common to every D68 subtype but not to other viruses and then developed a computer program that compares a large number of DNA sequences simultaneously.
In order to verify the test, the researchers used it to examine known panels of rhinoviruses and enteroviruses. Of the viruses they studied, the new test did not miss any known samples of EV-D68 and it did not falsely identify EV-D68 in samples that were known to be other viruses. There are two potential limitations of the test. Genetic sequences are not available for every virus so not all viruses were in the comparison panel used by the researchers. Also, EV-D68 could mutate and then the new test might not be able to detect the mutated virus.
In a recent article in the Denver Post, however, a physician who treated cases of EV-D68 in Denver, which was hard hit by the virus last year, says he is grateful for the new developments and thinks they will be very helpful in quickly identifying cases of the enterovirus if another outbreak occurs.