A new study published in the online journal mBio® reveals that a whole new universe of mysterious and unseen viruses exist in our world.

Biologists have found that raw sewage is home to thousands of undiscovered viruses, some of which could relate to human health.

Viruses are found everywhere and in almost every ecosystem on Earth. These viruses are the most abundant type of biological organisms and humans are more exposed to viruses on surfaces, in foods and in water.

At present there are approximately 1.8 million species of living organisms on Earth and all are host to unknown numbers of unique viruses, but from the 1.8 millions species only about 3,000 are recognized till date.

Viruses are small and tiny infectious agents that reproduce only inside the living cells of organisms and so they are not considered to alive.

Researchers looked for the genetic signatures of virus present in ordinary raw sewage from North America, Europe and Africa to measure the known present viruses, and detected 234 viruses that signify 26 different families, or types of viruses, which also include pathogens such as human papillomavirus.

Apart from viruses there are also bacteria present in sewage, so it was not surprising that the viruses that survived on bacteria subjected the known genetic signatures.

While researchers are aware of some viruses, the large number of genetic signatures found belonged to unknown viruses.

These unknown viruses could have an impact on human health and environment, Michael Imperiale, the study editor from the University of Michigan, said.

Some unknown human viruses may be opportunists that lie in wait for their host's immune system to break down and provide an opening, Imperiale said. However, the other viruses may be harmless or even helpful.

There's a theory out there that we may be infected with viruses that don't cause any disease and may have beneficial effects, Imperiale said.

Imperiale expects more discoveries related to virus to arise. I think this is going to be the tip of the iceberg of how many viruses are out there, he said. I think the ocean is going to top raw sewage by orders of magnitude, although they won't be found in such densities as they are in sewage, he added.

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