The average person is used to the idea that the human body carries a lot of bacteria, but may think that viruses only play a role when he or she is sick. A new study from Washington University in St. Louis, The Human Microbiome Project (HMP) has found that the average human carries 5.5 viral genera at any times. The tested population was health individuals, aged 18-40 half women and half men. Ninety-two percent of the test population had at least one virus. Subjects were only sampled up to five body sites-- the nose, skin, mouth, vagina, and stool—the results would probably been much larger if more sites of the body were tested and only DNA viruses were analyzed.
The most common viral genera found were herpesviruses, papillomaviruses, polyomaviruses, adenoviruses, anelloviruses, parvoviruses, and circoviruses. Most of the subjects did not have symptoms, but some did have low-level infections. Human adenovirus were found in 17% of the samples and various Herpesviruses were very common.
What are the implications of this study? One is that the study reaffirms the importance of hand washing and other sanitation measures, even if a person is not displaying signs or symptoms of a viral infection, to avoid potentially spreading viruses. Another is that the viruses may be booster the immune system by “priming” and protect against low-level infection. Future study along these lines may reveal important implications for the immune system--it is possible these viruses are different from viruses that cause current disease.