Researchers have recently announced the discovery, not of a new type of virus, but a very old one. However, despite its long and rich history, the virus, which is being called "crAssphage," had never been seen before state-of-the-art technology made it possible for scientists to explore new, microscopic, worlds. Its smallness made crAssphage undetectable without modern techniques, even though it is estimated to be in over half of all people, is believed to have existed about as long as humans have been human, and may have an influence on its host bacteria’s host human’s diabetes risk.
The meteoric rise of the virus—a bacteriophage, a type of virus that infests bacteria—has seen it go from being unknown and invisible to being recognize as the most common type of virus in the human intestine carried by a majority of human beings and in significant numbers—DNA from the virus was found in nearly three quarters of the samples the researchers studied, from all around the world. Its unusual-sounding name indicates that it is the first bacteriophage discovered using Cross-Assembly genome modeling software. As with many interesting discoveries, it was found in the search for something else. Researchers studying intestinal microflora were using the software to catalogue and classify the various kinds of bacteria inhabiting the digestive tract by reading the bacterial DNA when they came across genetic code they had never seen before. They quickly confirmed that no one else had either.
Nestled snugly inside bacteria, crAssphage doesn’t directly affect the humans it is carried in. However, the Bacteroides microflora species it infects live in the abdominal cavity, where they play a role in obesity and weight regulation. When crAssphage attacks Bacteroides species bacteria, researchers have suggested, this may help clear the way for a competing kind of microflora called Firmicutes. There is known to be an association between a higher ratio of Firmicutes to Bacteroides and obesity.