A virus that lives in the human gut has just been discovered, and to the surprise of scientists, it can be found in about half the world's population, according to a new study.

While it's not yet clear exactly what the virus does, scientists are eager to find out whether it promotes health or influences susceptibility to certain conditions, said researchers at San Diego State University.

The researchers first uncovered hints of the virus after analyzing DNA from fecal samples of 12 people and found a cluster of viral DNA that all the samples had in common.  

Next, the researchers searched a large database of genetic sequences in samples taken from people living on several different continents, looking for the virus's DNA sequence, and found the virus in 75 percent of samples of human feces. However, some of these samples were from the same person, so after taking this into account, the researchers estimated that the virus dwells in about half of all people.

But how could such a common virus go unnoticed for so long? One of the reasons may be that previously, most researchers compared DNA from current samples only to DNA sequences already known to exist, a researcher said. But in the new study, the researchers first compared the DNA in their samples to one another, looking for common sequences.

The new virus, which the researchers have named crAssphage, is a type of virus known as a bacteriophage, meaning it infects bacteria. It's likely that crAssphage infects a very common type of gut bacteria called Bacteroidetes, according to the study.

Although the researchers have shown that the virus DNA exists in nature, they have not yet been able to get the virus to replicate in the lab, or get a picture of it.

According to the team, CrAssphage has the genetic fingerprint of a bacteriophage – a type of virus known to infect bacteria.

The researchers think the virus could be involved in controlling the number of Bacteroidetes bacteria in the gut.

Phages may work to control the behavior of bacteria they infect – some make it easier for bacteria to inhabit in their environments while others allow bacteria to become more potent. They are critical components of our gut ecosystems, helping control the growth of bacterial populations and allowing a diversity of species.

But the virus is present in more than half the human population, and researchers say it could play an important role in the development of obesity and diabetes mellitus.

While there are myriad different kinds of gut bacteria, two groups – Bacteroidetes and Actinobacteria – have been associated with weight. According to previous studies, obese people have fewer bacteria from the Bacteroidetes group than thin people and more from the Actinobacteria group.

And according to the San Diego study, the new virus, crAssphage, attaches to the cells of the Bacteroidetes bacteria, hijacking the cells, a move that would further decrease the amount of Bacteroidetes in the gut, elevating the risk of obesity.

The new finding "adds another piece to the puzzle" in helping researchers understand how microbes in the intestine affect human health, experts of infectious disease think. Much more research will be needed to see how this virus interacts with  bacteria in the gut and how it could potentially affect health, they said. There are definitely a lot of avenues of research that the discovery of this [bacterio]phage will open up.

But just because the virus is common doesn't mean it's benign. The fact that it's there in so many people means that whatever it's doing is not causing something rare, researcher said. Because there are enough common conditions that affect humans, these viruses may have a role there, especially obesity and cancer as examples of such conditions.

After CrAssphage scientists discovered another virus named Bourbon virus for the country where the patient lived, is part of a group of viruses called thogotoviruses. Thogotoviruses have been linked to ticks or mosquitoes in parts of Europe, Asia, and Africa, Bourbon virus might also be spread through tick or other insect bites.

This is the first time a virus in this group has been shown to cause human illness in the United States and only the eighth known case of thogotoviruses causing symptoms in people.

Finally the discovery of Bourbon virus, HEV68 as well as CrAssphage   and some other viruses associated with thrombocytopenia syndrome in China, leads CDC researchers to believe that other undiscovered viruses are likely causing people to get sick and they number at least 300.000 of them.

There are many other microorganisms to be discovered in nature that may help in explaining of many infectious and noninfectious disease that remained obscure till update. In this way scientists recently discovered a new type of bacteria Genus thorseilla from family Thorselliacea that may help in battle against malaria disease and many other of them. Also related to this, scientists discovered a new type of fungi called Hirtclavula elegans and newest parasite called chytride.

But what remain curious are prions that are being intensively studied for their increasing role in many disease, especially neurodegenerative disease such as: Parkinson, Alzheimer, Huntington, depression, multiple sclerosis, autism etc.


  • http://www.scientificamerican.com/article/newly-discovered-virus-lives-in-half-the-world-s-population/,
  • http://www.cdc.gov/media/releases/2015/a0220-newly-discovered-virus.html,
  • http://emperie.eu/results/newly-discovered-viruses/,
  • http://www.usatoday.com/story/news/2015/02/20/new-tickborne-virus/23742135/,
  • http://www.bbc.com/news/health-28440006,
  • http://www.diabeteshealth.com/type-1/newly-discovered-virus-linked-to-obesity/,
  • http://www.huffingtonpost.com/2014/07/25/crassphage-newly-discovered-virus-gut_n_5618338.html,
  • http://theocoteanewsletter.com/2014/10/22/viruses-bacteria-and-your-immune-system/.

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