Dormant viruses may cause motor neuron disease when awoken

Human endogenous retroviruses may cause or contribute to some forms of amyotrophic lateral sclerosis

Sleeping viruses that lurk inside the human genome may "reawaken" and contribute to the development of motor neuron disease, according to new research published today in the journal Science Translational Medicine.

Human endogenous retroviruses (HERVs) are ancient microbial remnants that integrated into our chromosomes during repeated infections that occurred over several million years of our evolution. Although accounting for up to 8% of human DNA, most of them have acquired multiple genetic mutations that made them harmless, and are usually considered as "junk" DNA.