Of those infected , less than 10 % mutate as a result of the genetically re-engineered measles virus .
The current version is 622 words excluding alternative ending. -- > In 2012 , a genetically re-engineered measles virus , originally created as a cure for cancer , turns into a lethal strain which kills 90 % of those it infects , mutates 9 % into predatory , nocturnal mutants called `` Darkseekers '' who are extremely vulnerable to sunlight and other sources of UV , with only reaining 1 % immune .
I Am Legend -LRB-film-RRB-