I must say I have had a lot of fun playing Plague Inc. on my phone, though I feel that henceforth this is now going to be on occasional game at odd moments. I have played through and successfully wiped out humanity on Normal Difficulty for all seven different pathogens. I do have a generally winning strategy, which in its simplest form is one that Mrrx explains in this post: infect everyone before getting noticed, and then quickly ramp up the symptoms to Major Organ Failure, and watch humanity die out. However, while the differences between the different pathogens are subtle, they are there, and this basic strategy has to amended depending on circumstance. For what it is worth, what follows is my “guide” for this somewhat macabre little game.
Location, location, location…
The first decision, once one has actually entered the game world (having chosen pathogen and, if unlocked, altered the gene code), is which country to start. India and China are very popular starting countries from what I can gather, for two very good reasons. Both have large, generally poor populations, which means your initial spread is quite easy. Secondly both are also connected to air and sea routes, aiding the global spread of the plague. I have successfully started plagues from both locations, but there are other possibilities. Firstly the slower initial start-up in advanced countries is not necessarily a hindrance so long as one controls the symptoms, and a country like the UK has some of the best international connections for global spread. Another option is to start in one of those countries that is difficult to infect – Greenland, Madagascar, or New Zealand, on the theory that way at least one of them is out of the way from the start. Some consideration should also be given to it being a hot or cold country, as this gives some inbuild resistance to that climate zone. In particular if one starts in a hot country one has to consider spending some DNA points on cold resistance as the arctic countries can be difficult enough to infect either because of their remoteness (Iceland), their sparse population (Canada), or both (Greenland) without the added malus of a poorly adapted pathogen. From hotter nations I personally have also found Morocco and Angola to also be amongst the last countries to be infected more than once.
Pay attention to the news
There are usually a few random events in each game. Sometimes these can influence your strategy. In one memorable game an news article popped up about increased bird migration, so I invested some DNA points into that transmission method. Another news article came soon afterward about how bird migrations were at extreme levels. I quickly got the second level of bird transmission, and I have never seen the world get infected so quickly.
Infect the world
Apart from circumstances like the above, the most reliable way of infecting the world is through getting both Air and Water transmission vectors to level 2, which then unlocks Extreme Bioaerosol. In most circumstances that will suffice, though if you are having difficulty with certain countries it may be worth while finding another vector. If the plague is not yet spotted either increasing the hot/cold resistance of the pathogen (as applicable) or adding in some extra transmission vectors such as bird or animal can help overcome those hurdles. If the plague is already spotted make sure both coughing and sneezing symptoms are evolved, as they increase infectiveness without much increasing severity (thereby meaning you will not trigger much faster cure rates).
Devolving Transmission and unwanted symptoms
Once you have infected humanity, devolve all those transmission vectors. You will get DNA points for doing so that you can then re-invest into abilities to slow cure progress, or increase lethality. Only do this, however, once you get the message there are no healthy humans left. Likewise if, while still infecting people, symptoms mutate it is often worthwhile to devolve them and reduce the chance of detection, and in all pathogens but the Virus you will also gain DNA.
Dead people cannot conduct research into the cure
There are a number of abilities that inhibit cure research. Two of them slow the overall progress, and these should be priorities to research ideally before the plague is spotted. Then there are three which take off a few percentage from the cure research. While these can help you eke out enough time to kill humanity, once you are spotted the first focus has to be to kill people. Dead people conduct no research. Once you are spotted, or if cure research is progressing too quickly, evolve Total Organ Failure and watch the death toll mount. As people die you will benefit both from more DNA points and reduced research capability of humanity. Those DNA points you can place into the research-inhibiting abilities, but also consider the Coma, Paralysis, and Insanity symptoms all of which make the cure harder for humanity to achieve. They also increase lethality – so stop research both by making the cure intrinsically harder to achieve and by killing off the researches. Coma and Paralysis can be unlocked from Total Organ Failure, making them preferable in my view to the Genetic Reshuffle ability.
If you have been spotted before fully infecting humanity, and have needed to increase lethality to disrupt the cure, remember you can then devolve the lethal symptoms to reduce lethality to concentrated on infecting the remaining healthy humans. Otherwise you can kill off the infected before they infect the healthy.
Learn your pathogen
As I said at the start, the differences between the different pathogens are subtle, but they are real. The Bacterium is the first, and the reference point for all the others.
The Virus pathogen will both mutate symptoms more rapidly and require DNA to devolve symptoms. Therefore it becomes trickier to avoid detection. However, once humanity is infected the Virus mutate ability will mean symptoms evolve quickly, and generally speaking lethality will resolve itself.
The Fungus pathogen has one particular hurdle that can be frustrating to overcome: it does not travel well. This makes infecting the usual difficult suspects even more difficult. Patience is required, and do not expect the quick infection rates other pathogens can offer.
The Parasite is probably my favourite pathogen, as the pathogen-specific ability both increases transmission and decreases the likelihood of being detected. This makes it much easier to fully infect humanity, and indeed one can have involved a lethal symptom and be killing people before detection. Once detected it is vital to massively increase lethality to wipe out humanity before the cure gets starting.
The Prion is a difficult pathogen to cure, but also has a twist – it takes time for new symptoms and the like to take effect. This means you have to plan ahead a little more than you do with other pathogens. Increasing lethality will take some time to take effect.
The Nano-Virus turns some of the ordinary gameplay on its head, because you are spotted from the start. You do have more ways to inhibit the cure research through pathogen-specific abilities, but you must concentrate on infectiveness. A few points to help delay the cure, and then everything on infectiveness, including non-lethal symptoms.
Finally the Bioweapon, and once again this one radically changes the gameplay. This pathogen is natively lethal – and it will increase its lethality naturally over time. There are pathogen-specific abilities that can delay and reset this lethality, but you are from the start in a battle against your own lethality. Once again this means concentrated on infection. The inbuilt lethality to this pathogen will also mean you get spotted relatively early, so once again consider non-lethal infectious symptoms and immediately devolve any lethal symptoms that mutate.
If you have unlocked the game before you start you can modify your gene code somewhat with special abilities (unlocked through a successful game). Make sure that your strategy for any particular game plays to the strengths that you have selected.
Mostly though do not take this game too seriously. Wiping out humanity is not the most polite thing to do, and taking a moment to reflect on what this would mean in reality … well, my Asperger’s makes it very easy for me to take such thoughts seriously. Good source material for dark short stories, but an unfortunate source also if nightmares. It may sound silly, but avoiding potentially depressing allusions is something I have to take seriously for reasons I will try to explain one day, but this is not the post for that. However, my principle defence against negativity are the names I give my plagues. So for examples, Frog started in France, Siemens in Germany, AAPL in the USA, and ABBA in Sweden. Yes, my sense of humour might be a little strange, but it made me smile.
Overall I very much recommend this game as an intriguing exercise in managing various different factors, and as a something even a little thought-provoking. I have not played either expansion, and currently do not intend to do so.