Infectonator

Infectonator is a flash game developed by Toge Productions. It is a simulator game where you have to infect as many people as you can with a virus that turns humans into zombies. Infectonator features a set of 13 levels where the goal is to place a virus among a crowd of people to turn all victims within range of the virus into flesh-eating zombies, creating a chain reaction wherein the zombies you created will go after uninfected people and turn them into zombies too. Ideally, you should place your virus where it'll infect a large number of people so your chain reaction can get a strong start. As the zombies roam around the room trying to spread the virus, they'll eventually die off and drop coins that can be collected to buy upgrades with; if all the zombies onscreen die and no one else got infected, the chain reaction ends (although some levels give you grenades that you can use to kill off any stubborn survivors that weren't killed by the virus). Once it does, you get to move on to the next level if you've killed enough people to meet the current level's quota; otherwise, if you fail to meet the quota, the game ends.