Human Virome

Viruses are dominant entities in the biosphere and parasitize all cellular life forms. The relative abundances of different classes of viruses are dramatically different between prokaryotes and eukaryotes. In marine, soil and animal-associated environments, virus particles consistently outnumber cells by one to two orders of magnitude. It is estimated that 10 quintillion (1030) viral particles are inhabitants on our planet and in most ecosystems, there are 10 viruses per each bacterium. Viruses are major ecological and even geological agents that largly shape processes such as energy conversion in the biosphere and sediment formation in water bodies by killing off populations of abundant, ecologically important organisms such as cyanobacteria or eukaryotic algae. Like transposons, viruses and plasmids, parasitize all cellular organisms and they appear to encompass the bulk of the genetic diversity on earth. They are intrinsic to any evolving system of replicators, imply that virus-host coevolution had been the mode of the evolution of life ever since its origin. High-throughput sequencing technologies have revolutionized how we think about viruses. Investigators can now go beyond pathogenic viruses and have access to the thousands of viruses that inhabit our bodies without causing clinical symptoms. By studying their interactions among themselves, with other microbes, and with host genetics and immune systems, we can learn how they affect health and disease. This article reviews current knowledge of diversity of the human virome in physiologically healthy individuals. It focuses on current data from metagenomic studies and discusses the contribution of bacteriophages and eukaryotic viruses to human health.