We hear about humans having and needing 鈥済ood bacteria鈥�. Are there similarly 鈥済ood viruses鈥� in our bodies? (continued)
Penny Jackson,
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Barrow-in-Furness, Cumbria, UK
In addition to the bacteriophages discussed in previous responses to this question (31 December), there are a few viruses where an infection appears to be beneficial. For example, herpes by certain bacteria.
There is also a surprising benefit to infection by some retroviruses, which are types of viruses that integrate into the host cell鈥檚 DNA, modifying the genetic code. This integration can be permanent. It can even get passed on to offspring, making these viral parts common or even universal within the genome of a species (or wider, depending how far back the integration occurred), especially if they provide an evolutionary advantage.
This is the case for at least 8 per cent of our DNA, and some sources say possibly closer to 50 per cent. Not all their functions are known, but some have been identified as possibly having benefits for the immune system. But some probably aren鈥檛 so helpful, and are associated with a higher risk of contracting certain diseases.
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