The original Class 3 Outbreak was released in 2010. It has been played over 2.4 million times by over 1.4 million people.
The beta for a new Class 3 Outbreak based on an editor was released in 2011. This allows you to make your own zombie apocalypse anywhere in the world. Over 5 million games have been played by over 1.2 million people.
Players have created over 20,000 maps, with over 2,500 of them featured on the home page.