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Experts in virology suggest that approximately 320,000 distinct mammalian viruses exist, with the potential for countless more worldwide. Accurately quantifying this would demand significantly more funding and resources than currently allocated to viral research. While many viruses reside within and on our bodies—collectively known as the virome—they don’t always cause illness; often, they remain inactive. Numerous aspects of viruses, such as their mechanisms for cell entry and replication, remain poorly understood. However, advancements like the VirScan blood test can reveal every infection a person has ever encountered.
A groundbreaking new test, developed by researchers at Washington University in St. Louis, can identify nearly every virus known to impact humans and animals. Known as ViroCap, this test also has the ability to detect previously unknown viruses, provided they share certain genetic similarities with known ones.
Kristine Wylie, assistant professor of pediatrics at the university's McDonnell Genome Institute and co-author of the study published in Genome Research, states, “The use of high-throughput sequencing is thrilling because of the vast amount of data we can produce quickly.”
The test was created by researchers who condensed one billion viral genetic base pairs into 200 million functional sequences. They then extracted small segments from each sequence, transforming them into “probes” capable of identifying genetic matches in patient samples.
With its extensive virus database, ViroCap surpasses the sensitivity of standard polymerase chain reaction (PCR) tests, integrating two million RNA and DNA gene sequences into a single test. Researchers can analyze viral genetic sequences and identify matches from conserved genes collected in public databases like the Viral Genome Project.
ViroCap can identify a wide range of viruses, from severe threats like Ebola and SARS to common culprits such as rhinoviruses and noroviruses, which cause colds and stomach flu. Its sensitivity is so high, Wylie notes, that it can even detect genetic variations of viruses, something conventional tests often miss.
ViroCap was tested on blood and stool samples from a small group of children with unexplained fevers. While standard tests identified 11 viruses, ViroCap detected an additional seven. Overall, ViroCap found 52 percent more viruses across all samples compared to traditional methods.
“There are real-world clinical uses for viruses that go undiagnosed,” Wylie explains. “A known virus might appear in an unexpected location. Doctors could discover a virus they didn’t suspect was causing an illness. For instance, during our study of children with fevers, we found a virus in one patient’s blood that we wouldn’t have typically searched for.”
Patients with unexplained fevers are frequently given antibiotics when no virus is detected. Wylie suggests that ViroCap could help reduce the unnecessary use of antibiotics.
By adapting the test, researchers could also identify drug-resistant mutations and changes in regions that affect vaccine efficacy. It may also shed light on why some individuals carry viruses without showing symptoms. “On average, we found people carry about 5.5 different viral genera capable of causing illness in certain individuals,” Wylie explains. “In our study of children, rhinoviruses, which cause colds, were equally common in kids with and without colds. This highlights the need to understand what triggers symptoms in some cases.”
Additionally, ViroCap can contribute previously unknown viral DNA to the database of recognized viruses. “The more comprehensive our genome data, the more insights we can gain,” she adds.
With its broad potential, the team has made the test accessible to any researcher interested in utilizing it. However, widespread use may still be far off. “From a research perspective,” Wylie states, “this opens up an entirely new realm. ViroCap is significantly enhancing our ability to study viruses in greater detail.”
