Homo Derelictus

When children in a cluster of small villages in the north-east of England develop diseased kidneys, they are found to have an abnormal gene, previously only found in Archaea; the most primitive organisms on Earth.

A rapid scramble by medical authorities, led by one of the children's fathers, cures the abnormality with a variation of the CRISPR technique and things seem to return to normal.  

Yet soon after, multitudes of all ages and across the world, are struck down; their bodies rapidly regressing to a pre-hominid state that the scientific community labels, Homo derelictus. Infected by whole Archaean organisms, the diseased seek isolation and quickly die.

The race is on to preserve what is left of Homo sapiens, a struggle that must be global in its reach and unite all of what remains of humanity.