In Plague Inc, there are different symptoms you can buy and this puzzle is identical to the symptom upgrade map. Here is a labeled version of the full symptom map.

Another notable thing about Plague Inc symptoms is that to buy them, you have to pay their cost in "DNA points". Note the DNA symbols on certain symptoms in the puzzle. You can find the DNA cost of all the symptoms here: https://plagueinc.fandom.com/wiki/Symptoms