Sewer-Exploring Scientists Discover 10 Times the Number of Viruses Previously Charted . . . In Only 3 Cities

According to an article appearing in the American Society for Microbiology's journal, mBio, a group of raw sewage-examining scientists have discovered more than 43,000 viruses in the wastewater of a mere three cities: Pittsburgh, Pennsylvania; Barcelona, Spain; and Addis Ababa, Ethiopia.

This number might not sound like much. After all, there must be thousands of known viruses, right?

Indeed, there are. Scientists have charted roughly 3000 of them. It's just that the good folks behind these findings have found a minimum of 43,381 bugs lurking in the filth-lined sewers beneath the streets of just three cities.

But before you begin panicking and digging through your dusty volume of Nostradamus, it is important to note that even the microbiologists authoring the mBio article dismiss their findings as "unsurprising." Virologists have made it plain that our present knowledge of viral diversity is, at best, limited to a very small fraction of the viruses in the world.

Part of our collective ignorance stems from the fact that the vast majority of viruses in the world do not pose any threat to human health, so epidemiologists have not spent as much time or money investigating them. While many viruses can, in fact, infect human beings, only a fraction of those actually result in disease. To put it into context, of the 234 known viruses the scientists identified among the more than 43,000 they found in the raw sewage sloshing around beneath Spanish, Ethiopian, and American Rust Belt streets, a mere 17 (or slightly more than 7 percent), including such comparatively innocuous bugs as nasopharyngitis (the common cold) and novovirus (the virus responsible for 90% of the world's  cases of stomach flu), infect human beings.

It makes financial sense for scientists to devote their often tightly-regulated resources to investigating the viral causes of human disease rather than, say, the bacteriophages scientists believe make up four-fifths of the world's as-yet unidentified viruses. The other twenty percent is broken up between humans and every other form of life on the planet from algae to fungi to worms and dandelions. In other words, it's not like there are legions of undiscovered viruses lining up to wipe out humanity, though, of course, there might be a few.

What is significant about this study and others like it is not the fact that it has uncovered so many previously unknown viruses but that it aims to study "the origin of emerging pathogens and the extent of gene exchange among viruses" so that we may better understand how viruses spread and mutate.

Still, this is not something one would want to contemplate while using a public restroom...