Raw sewage: Biologists gush over world of undiscovered viruses

Here’s a posting from the “ick” files. Scientsts are now delving into an uncharted environment to study human and other viruses: raw sewage.

In a study published Tuesday in the online journal mBio, researchers from the U.S. and Spainfound that untreated human wastewater -- “the effluence of society,” they wrote -- contains an incredible diversity of viruses ... and that the vast majority are viruses we hadn’t known of before. Click for the abstract.

At this point, biologists know of about 3,000 different viruses, representing 84 different viral families -- but they suspect that those known bugs are just the tip of the iceberg.

To find out what they were missing, the researchers genetically analyzed untreated wastewater from Pittsburgh; Barcelona, Spain; and Addis Ababa, Ethiopia. The effluence that they studied indeed contained a wealth of viruses -- 234 known bugs from 26 different families.

Among them, the researchers found 17 that infect humans, including human papillomavirus and the flu-causing norovirus. Many of the other known viruses came from plants -- which would make sense, since plant viruses are known to dominate the viral landscape in human fecal matter.

But the researchers also found that that the vast majority of DNA signatures they found didn’t match any known viruses -- meaning, the authors wrote, “that the vast majority of the viruses on Earth have not yet been characterized.” Yikes.

Whether they’re friend or foe is hard to say -- some could be opportunistic bugs waiting for a crack in the body’s defenses; others may be beneficial, or at least benign.

The biologists say they plan to study other environments, such as the ocean, and to analyze the richness of the viral communities there. The more diverse the host organisms are, they write, the more diverse those viruses will be.

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