Ada Wong is still working for a mysterious benefactor, and has another strain of the Plaga parasite
After the events of in the Eastern Slav Republic, Ada Wong escapes with a dominant strain of the Plaga. It’s still unclear just who she’s dealing with, but we can rule out Umbrella, Wesker, and TriCell, as they’re either no longer living or defunct. Plus, Ada has double-crossed pretty much every single organization on the planet at this point, so even if we did find out whom she was working for, it wouldn’t be uncharacteristic of her to suddenly switch sides.
Someone, somewhere is hoarding all these viruses, and with Umbrella out of the picture for the very first time (or are they?), it’s still a mystery who is continuing to create all these horrible plagues. All we know is Ada appears to be their number one supplier, and it looks like she’s up to her old tricks again in Resident Evil 6.