Viruses are traditionally seen as pretty bad things. In Hollywood, it was always some mysterious virus that left only a few people on Earth or gave rise to a horrific zombie apocalypse. They're the things we think about when we hear "epidemic" or "plague" (even when the black death is actually caused by bacteria). "Virus" is even what we call the pesky malware that can harm our computers. However, according to a new study, there are plenty of "good" viruses out there, too.

"The word, virus, connotes morbidity and mortality, but that bad reputation is not universally deserved," researcher Marilyn Roossinck said in a recent statement.

Roossinck, a professor of Plant Pathology and Environmental Microbiology and Biology at the Pennsylvania State University, recently reviewed available literature and scientific studies of viruses and detailed her findings in the Journal of Virology.

The researcher explained how viruses are less-so monsters from horror flicks and more like the characters in a spaghetti western. Some are bad, some are ugly, and some are plainly good.

"Viruses, like bacteria, can be important beneficial microbes in human health and in agriculture," she said.

For example, many studies have revealed that the murine (mouse infecting) norovirus plays a role in development of the mouse intestine and its immune system (you can read more about that here). This is hugely different than the human brand of norovirus, which is infamous for causing severe digestive problems and has ruined many-a-cruise trip or restaurant outing. (Scroll to read on...)

Then there's the herpes virus. You read that right, herpes - the unmentionable sickness which boasts strains that can cause painful cold sores or (heaven forbid) an incredibly persistent and harmful sexually-transmitted disease (STD). According to a number of past studies cited in Roossinck's work, a latent herpes virus (one that is dormant) may naturally arm the cells they infect with the ammunition to kill both mammalian tumor cells, and cells that are infected with pathogenic viruses.

Roossinck detailed how researchers are just learning that much like the incredibly diverse microbiome of bacterial cells within the human gut, the gastrointestinal tracts of mammals are plush with viruses that seemingly just hang around doing... something.

In the case of microbes, those vast communities keep one another in check, preventing any one species from gaining too much ground and becoming a dangerous infection. Simultaneously, this city of co-existing gut microbes bolsters the immune system, attacking many intruders (mostly foreign bacteria) as one angry mob looking to vent their frustrations on an outsider. This is also why experts advise against over-using antibiotics. Not only can this help usher in an apocalyptic future where traditional drugs won't work, but it can also disrupt the balance of that microbial city, leaving a patient vulnerable to common bed-side infections, like Staphylococcus aureus (Staph). (Scroll to read on...)

So are the viruses members of this community in the same way? Roossinck concludes that we really can't know for sure just yet. However, their sheer numbers and diversity suggests that they have important functions. One suggestion has been that they are almost like trainers for our gut bacteria, infecting these microbes and modifying them to aid in digestion.

But what about in non-mammals? Researchers have known for a very long time that viruses strike at plants and fungi too.

In one noteworthy example, Roossinck mentions plant communities living in the hot soils of Yellowstone National Park. Bordering geysers and the "Artists' Paintpots," plants here are somehow able to withstand the muddy soil, which sometimes heats up to a stunning 122 degrees Fahrenheit (50 degrees Celsius).

Recent investigations determined that to live there, plants form a complex symbiotic relationship between fungi and the viruses that infect them. Field work and lab-side studies determined that this three-way 'agreement' could likely allow most plants to hash out an at-least struggling existance in these normally fatal temperatures. Even tomato plants were found to withstand up to 140 degrees (60 C) as long as all three members of the relationship were present.

"Viruses are beyond a doubt the coolest things I have ever encountered," added Roossinck. "They do truly amazing things with very little genetic information. I was always a little disturbed at the bad rap they get, so it was very exciting for me to find good ones."

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