The Bacteria is the basic template of all Plagues. It mutates automatically every now and then, and is the most basic of any plague, with not much activity and no unique traits. The Bacteria serves as the first and easiest plague to beat, and a starting point for every player (unless you started with the Shadow Plague or Simian Flu). Note that you will GAIN DNA for devolving.

Feel free to skip this section if you already know the basics of the game, as this section is aimed for those that haven't played Plague Inc before.

Upon starting, you will select a country. This is where the plague will start. To begin the game, you must click the red Play button (a red bubble with a white (isosceles) triangle pointing right) that appears where you click.

You will indirectly control the plague by evolving it to allow it to spread faster and kill.

When a new country is infected, a red bubble will appear that you can click for DNA. DNA can be used to buy symptoms, transmissions, and abilities for your plague. To open this menu you can click in the bottom left corner or press Q. DNA is also obtained by infecting and killing people.

You can also increase the speed of the game. 1 and P play at normal speed, 2 doubles the speed, and 3 triples it. SPACE will act as a pause.

To spend DNA, simply select a hex (the hexagons with a symbol) and click Evolve if you have enough DNA or double click it. To Devolve something, do the same, and you will get 2 DNA back (or lose DNA on some plagues).

While the virus spreads, Orange bubbles will appear which give DNA.

There are 3 bars at the bottom of the screen when you open the Disease menu.
INFECTIVITY is how fast your virus can spread.
SEVERITY determines how fast the Cure is completed (more on that later) and how fast your virus is detected. You want to make sure this doesn't rise early on.
LETHALITY is to be left for the end-game, as it is how fast the virus will kill.

You want to make sure Severity stays minimal. If any amount is present, a doctor will notice the virus and The Cure will begin, which will end the game if it is complete. Blue bubbles will begin to appear, which you can pop to slow down the speed of the cure. Severity will increase its speed, so be aware of it. The cure can also be slowed by certain abilities and by destroying the head country working on the Cure. If you always keep severity at 0, you can infect the whole world without triggering the cure.

Make sure to stay away from Lethality until the whole world is infected. This is not signified by the message "<plague name> needs to evolve to kill" but rather "There are no healthy people left in the world." Lethality will begin to kill the infected, and it should be saved until endgame, where the final goal is to eradicate humanity.

This guide is meant to be taken in a slow and steady approach. Do not rush, as it will work as long as the Cure doesn't start.

Genes improve the capabilities of your plague. They are unlocked by completing plagues, but you won't need these due to how simple the Bacteria is. In other guides, I will explain the Genes as they are recommended.

As any plague, you will automatically mutate symptoms. These can be kept or removed for some extra DNA (or remove it at a price for certain plagues). As a Bacteria, devolve these symptoms instantly to stay undercover and get a few extra DNA.

Begin in South Africa (or, if you prefer the exact countries, South Africa, Lesotho, Namibia, or Eswatini). This will provide us a small boost in hotter climates in the future. Pause the game afterwards if you are a first-time player, and follow the instructions in Exploring the Interface. Otherwise, skip to Early-Game.

Press the bottom left corner or the Q key. This is the Disease Menu, where you can see the status of the plague (Infectivity, Severity, and Lethality) and evolve the plague. In the top right corner, there will be 4 buttons. Overview will not be needed, ever. In the Transmissions tab, you will be able to evolve traits that allow you to spread through climates better, by plane, boat, insect, blood, and more. Under Symptoms, you will find abilities that can increase infectivity... at a cost. These are ones you want to avoid, as it will lead to the start of your untimely end. Finally, under Abilities, you will find traits that will improve effectiveness. This includes Drug Resistance, Unique traits (a group of traits only present in specific plagues), cold/heat resistance, and abilities to impede The Cure. It is important to note that whenever you see the message "<Plague name> has evolved <symptom> without using DNA points", go to Symptoms and devolve it instantly. Go back to the world map, but do not resume. In the bottom right, click the blue button. Here you will see a few things. The right side is the Cure Progress. This shows how much of the world COULD be working on a cure, how many ARE working on it, and how many CAN'T work on it - Working, Potential, and Destroyed, respectively. The center right shows the progress and ETA of The Cure. On the bottom left, you will see, from left to right, uninfected countries in blue, countries that are infected (partially infected pink, fully infected red), and countries that have been eliminated in black. In the center, you will see a pie chart of how many people in the world are healthy, infected, or dead.

If, mid-game, you have no symptoms and someone dies, don't worry- this is a natural disaster, a random event that kills a small portion of the population, usually 100 to 7000.

Pop Orange and Red bubbles and devolve symptoms until you have 50 DNA.
Open the Disease menu and, in the top right corner, click on Transmissions. Purchase Air I, Water I, and Water II.

Save up for 100 DNA.
Purchase Air II and Extreme Bio-aerosol in the same tab. Click on Abilities. Purchase Drug Resistance I, Drug Resistance II, and Heat Resistance I.

Save up for 30 DNA.
Under Abilities, purchase Cold Resistance I and Cold Resistance II.

Devolve any symptoms until you get the final "There are no healthy people left in the world" message. This is when you want to save up your DNA to prepare to end humanity.

Save up for at least 45 DNA, and obtain the message "THERE ARE NO HEALTHY PEOPLE LEFT IN THE WORLD."
If you've made it this far, it's time to kill.
Upgrade the following symptoms: Coughing, Sneezing, Immune Suppression, and Total Organ Failure. TOF will kill EXTREMELY fast, so make sure you do this only AFTER everyone is infected. If you have extra DNA, make sure you put DNA into other lethal symptoms (Coma and Necrosis, if you can).

Good job, humanity has ended and you're the reason why humans went extinct. You win!