The Cure is humanity's last defense against a plague.
Once a plague becomes spotted, cure development will begin shortly after. Plagues can be spotted due to symptoms, increasing in chance of being noticed when severity rises. If cure progress is at 100%, development teams will rush to infected countries and begin to cure the infected. Once all of the infected have been cured, the game ends. Delaying the cure is very important (evolve Genetic Hardening 1 and 2 to slow research, and evolve Genetic ReShuffle 1/2/3, or evolve stifling symptoms such as Coma and Seizures to further delay research, or make the plague deadlier to kill off valued research contributors). Warnings will be issued when cure development has reached 25%, 50%, 75%, 95%, and lastly, 100%. Even if the cure has been completed, evolving a trait that increases the work that is needed to cure (Such as Insanity or Genetic Reshuffles) will still setback cure progress, allowing the plague more time to eradicate humanity.
Every in-game day, each country will spend money on the cure research. This money will accumulate towards the total money needed to cure your plague, which can be found in the Cure graph in the World menu. If your plague is more severe or lethal, and a country has more deaths from your plague, they will spend more money. Also, the more dead people they have, the less money they can spend. If a country is in anarchy, they can no longer contribute. How much money they are spending can be found in their information screen. Abilities such as Genetic Hardening 1 and 2, and symptoms like Coma and Seizures will increase the money needed to cure you. Genetic ReShuffle will actually decrease the total money already spent. Another factor in cure speed is how much the researchers work, which depends on the difficulty setting. It is unknown how exactly this affects the cure progress, but it is obvious that the more they work, the faster the cure will progress.
Being a microscopic robot, the Nano-Virus can become immune to modern medicines making a conventional cure ineffective. What takes place instead is the Cure Broadcast, which is designed to activate the built-in kill switch. What makes the Cure Broadcast truly different is the fact that it starts at the beginning of the game. While the cure meter rapidly builds up if left unattended, the Nano-Virus has many more options to delay the broadcast.
On its own, a Necroa Virus is easy to cure as it lacks many cure delaying symptoms and abilities and inherently requires less time for a cure to be researched. Once zombies have been created, however, the cure becomes useless. Since the zombies are already dead, they cannot be cured and can continue killing and consuming healthy people, turning them into new zombies and in general keep on rampaging across the world even after the cure is fully completed.
In the Simian Flu DLC, the cure is instead developed by Gen-Sys, the company which developed and accidentally released the virus. Once they admit that they created the Simian Flu, they will take over all cure research from governments and use existing data to speed up the cure. They may set up labs near ape colonies to gather data and capture apes, as well as other countries with large ape population. If a Gen-Sys lab is successfully raided by rampaging apes, the cure progress will take a noticeable hit due to lost research.