The most common viruses in your body don’t make you ill. Instead, they infect the legions of microbes that live in your gut. These bacteriophages, or phages for short, number in their trillions. And the most common of them might be a newly discovered virus called crAssphage.
No one has seen crAssphage under the microscope, but we know what its genome looks like—Bas Dutilh from Radboud University Medical Centre pieced it together using fragments of DNA from the stools of 12 individuals. He found crAssphage in all of them. Then, he found it in hundreds more.
To study the microbes that live in a person’s guts, scientists will typically collect a stool sample, break all the DNA within into small fragments, and sequence these pieces. The result is a metagenome: a mish-mashed collection of DNA from all the local bacteria, viruses and other microbes.
Dutilh’s team, led by Rob Edwards at San Diego State University, analysed 466 metagenomes that have been added to public databases and found crAssphage in three-quarters of them. It’s there in stool samples from people in the USA, Europe and South Korea. It actually accounted for 1.7 percent of all the sequences that the team analysed—six times more than all the other known phages put together. You probably have it inside you right now.
Read the full, original story: Why Has This Really Common Virus Only Just Been Discovered?
