[DeathsHand]

The last thing I remember about Resident Evil, Wesker had all sorts of viruses and potential test subjects, and got his hand on Las Plagas, presumably to tinker with it and make some sort of GT-Virus Alexia Ashford Virus Plagas Fajitas...

So I'd say he's most obviously behind this new version of the Las Plagas, seeing as how he's been behind just about everything in the series ever since they discovered that gamers really like bad guys who wear dark sunglasses and black clothes...