MicrobeWorld

Biologists have described only a few thousand different viruses so far, but a new study reveals a vast world of unseen viral diversity that exists right under our noses. A paper to be published Tuesday, October 4 in the online journal mBio explores ordinary raw sewage and finds that it is home to thousands of novel, undiscovered viruses, some of which could relate to human health.

Viruses are everywhere: every moment of every day, humans are exposed to viruses on surfaces, in foods, and in water. However, our knowledge of the viral universe is limited to a tiny fraction of the viruses that likely exist. There are roughly 1.8 million species of organisms on planet Earth, and each one is host to untold numbers of unique viruses, but only about 3,000 have been identified to date.

To explore this diversity and to better gauge the numbers of unknown viruses that are out there, researchers looked for the genetic signatures of viruses present in raw sewage from North America, Europe, and Africa.

They detected signatures from 234 known viruses that represent 26 different "families", or types, of viruses. This makes raw sewage home to the most diverse array of viruses ever found.

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