Curious how many viruses have invaded your body over the course of your life? Now you can know.
Researchers have developed a DNA-based blood test that can determine a person's viral history, a development they hope could lead to early detection of conditions, such as hepatitis C, and eventually help explain what triggers certain autoimmune diseases and cancers.
The new test, known as VirScan, works by screening the blood for antibodies against any of the 206 species of viruses known to infect humans, according to a study published Thursday in the journal Science. The immune system, which churns out specific antibodies when it encounters a virus, can continue to produce those antibodies decades after an infection subsides. VirScan detects those antibodies and uses them as a window in time to create a blueprint of nearly every virus an individual has encountered. It's a dramatic alternative to existing diagnostic tools, which test only for a single suspected virus.
"The approach is clever and a technological tour de force," said Ian Lipkin, a professor of epidemiology and director of the Center for Infection and Immunity at Columbia University, who was not involved in the creation of VirScan. "It has the potential to reveal viruses people have encountered recently or many years earlier ... Thus, this is a powerful new research tool."
Scientists on Thursday reported intriguing findings from their initial tests of 569 people they screened using VirScan in the United States, South Africa, Thailand and Peru. They found that the average person has been exposed to 10 of the 206 different species of known viruses -- though some people showed exposure to more than double that number.
"Many of those [people] have probably been infected with many different strains of the same virus," said Stephen Elledge, a professor of genetics and medicine at Brigham and Women's Hospital and Harvard Medical School, who led the development of VirScan. "You could be infected with many strains of rhinovirus over the course of your life, for instance, and it would show up as one hit."
In addition, he said, certain viruses were far more common in adults than in children, who presumably have yet to encounter much of the world's viral landscape. People infected with HIV tended to have antibodies against many more viruses than people without the disease. Researchers also saw striking geographic differences in the way viruses affected different populations. People in South Africa, Thailand and Peru generally displayed antibodies against many more viruses than people living in the United States.
"We don't know if this has to do with the genetics of the people or the strains of the viruses that are out there," Elledge said of the differences by country. "Or if it has something to do with cultural habits or sanitation."
Elledge said the VirScan analysis currently can be performed for about $25 per blood sample, though labs might charge much more than that if the test becomes commercially available. He also said it currently takes two or three days to process and sequence about 100 samples, though that speed could increase as technology improves.
Ultimately, Elledge said he hopes the test could be used to more quickly detect conditions, such as HIV and hepatitis C, which patients can carry for years before displaying any outward symptoms. Experts believe VirScan also could lead to insights about the role long-ago viral infections play in the later development of certain cancers and autoimmune diseases such as Type 1 diabetes and multiple sclerosis.
"There are a lot of chronic diseases where we think a virus might be involved, but we can't quite pinpoint it ... Right now we can't quite make the connection," said Vincent Racaniello, a professor of microbiology and immunology at Columbia, who was not involved in developing VirScan. "I think this is really going to be helpful. It's very cool."
Racaniello said he envisions a day when patients will get the VirScan test as part of a regular checkup.
"This is going to be routine, I think," he said. "It'll be good to know what viruses have been in you."