Gregory Storch, a Washington University virologist and one of the study's co-authors, noted that while we're comfortable with the idea of our bodies constantly harboring bacteria, the idea of viral pathogens living in our healthy bodies isn't something that has been well studied.
"Most everyone is familiar with the idea that a normal bacterial flora exists in the body," Storch said in a statement. "Lots of people have asked whether there is a viral counterpart, and we haven’t had a clear answer. But now we know there is a normal viral flora, and it’s rich and complex."
It could be that the presence of viruses helped keep the immune system primed -- a form of protection against full-blown disease. The subjects in the study didn't display symptoms of illness like coughing, sneezing or fever. But in some cases, researchers found signs of low-level infections.
Samples were taken from several locations in the body: nose, skin, mouth, stool and vagina. Researchers found evidence of the viruses that cause the common cold and pneumonia in some samples. And non-sexually transmitted strains of herpes were found in 98 percent of the mouth samples. Papillomavirus, which in some cases increase the risk of cervical cancer, were found in 38 percent of the women.
The findings, though interesting (and possibly also terrifying to hypochondriacs), shouldn't be cause for concern.
Evidence of "normal viral flora" within an otherwise healthy human body should bolster support for standard sanitation and hand-washing practices; viruses don't require a sick person to spread around. And researchers still have to figure out how to distinguish between the viruses that might be making people sick and the ones that are not causing noticeable symptoms.
These findings may be, however, the tip of the iceberg.
“We were impressed by the number of viruses we found,” said the study's lead author, Kristine M. Wylie, who is a pediatrics instructor at Washington University. “We only sampled up to five body sites in each person and would expect to see many more viruses if we had sampled the entire body.”