When a patient is suffering from an unknown illness, doctors have a couple of options: They can run tests that either confirm or deny suspicions about the presence of specific viruses, or they can run wider-ranging tests, which might reveal the presence of a greater variety of potential infections, but at a lower level of sensitivity. Both require doctors to first make educated guesses at what might be causing a patient’s illness.
That might be about to change. Researchers at the Washington University School of Medicine in St. Louis have developed a test kit that they say can scan a patient for almost every virus known to infect people, in extraordinary detail, even if the viruses are present at only “very low levels.” “With this test, you don’t have to know what you’re looking for,” said Gregory Storch, the lead author on the study (pdf). Effectively, Storch said, the test “casts a broad net” and signals the presence of any recognized viruses at once, savings doctors time when the cause of an illness is unknown.
To develop the test, a research team collaborating with the university’s McDonnell Genome Institute indexed the unique DNA or RNA sequences of every known virus to affect not only humans but animals, too—some 2 million in all. Provided with a sample of the patient’s stool, blood, or nasal secretion, researchers could then run the test to look for any matches.
In two clinical trials involving a total of 22 subjects, the test, called ViroCap, detected 32 viruses; standard testing through genome sequencing on the same groups revealed only 21. The developers of the new test say it is accurate enough that it can identify individual strains of related viruses—something current tests cannot do. While standard testing of the 22 subjects identified the presence of influenza A, for example, the ViroCap test identified the precise type of flu: H3N2, a subtype known to be the cause of 36,000 US deaths during the last flu season.
Storch says the test could be easily modified to include additional genetic sequences when new viruses are discovered—and eventually, study co-author Kristine Wylie says, it could could be expanded to detect other kinds of pathogens, such as bacteria, fungi, and other assorted microbes. The team behind ViroCap likely has several years to go before the test is clinically available, as the process still needs additional testing for accuracy. Meanwhile, the group will make the technology freely available to fellow researchers worldwide, to further its development.