A new mutation has just been unleashed in the “sick” (read: excellent) strategy game Plague Inc.

Plague Inc. has just received its fifth mutation update. And with it comes the new Necroa virus plague type, along with a few other game enhancements.

The Necroa virus, which may be customized with five new genes, is said to be “an aggressive, unknown virus with ‘extreme regenerative abilities.’”

Its arrival in Plague Inc. signals the dawn of a new, apocalyptic challenge featuring new gameplay, graphics, and evolutions.

It also warrants the use of active abilities such as the Zombie Horde in the battle against Z Com aka “humanity’s last defense against the dead.”

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The new Plague Inc. update also delivers a couple of interface enhancements. One, there’s a new population percentage bar that lets you see the status of a country. And two, the DNA animation now shows how much DNA is being collected.

Further, the update brings language support for French, Italian, Portuguese, and Spanish.

New events, news, and achievements are included in the update as well.

Compatible with iPhone, iPod touch, and iPad running iOS 4.3 or later, Plague Inc. is available in the App Store for $0.99.

As noted in our review of the game, the main challenge of Plague Inc. lies in having to strike a balance between a plague type’s severity and lethality. Can you do just that with the new Necroa virus?