Plague Inc. Wiki
General Information Strategy Guides
Little helper.png "The world is dark and gloomy. Boring governments worldwide have banned holidays, laughter, and celebrations. Humanity has forgotten how to have fun - people dress in gray and spend all their time working. Luckily, the Neurax Worm has teamed up with Santa and is determined to infect the whole world with joy and happiness.
Can Santa's little helper make a miracle happen?"

— Plague Inc., Santa's Little Helper introduction paragraph.

Santa's Little Helper is a Christmas-themed scenario that was added in Mutation 1.10.[1]


  • This scenario was created exclusively for the 2014 holiday season.
  • It is based off the Neurax Worm DLC, which means that players MUST use this to gain victory.
  • In this scenario, one has to make all the people in the world happy.
  • The default name for the disease is XMA-3, an obvious reference to the theme.
  • The scenario begins with every country having closed airports, ports and land borders.
  • As the player begins to infect, they should evolve certain transmissions, symptoms, and abilities to make all these outlets open up.
  • Severity is replaced with "Happiness", which has similar effects to Severity but will also encourage infected people to spread the infection further and hinder the progress of the cure.
  • Once a country is fully infected and if certain symptoms are already active, it becomes "eternally happy" and will open its airports, ports, and borders if it has not already done so.
  • Countries that are eternally happy also permanently stop all contribution to the cure effort. Once every person in the world is infected, the game will end, stating that the player has made the whole world happy and that humanity will have a great future ahead of them.









After Festive Tendrils:


  • Unlike normal Neurax Worm, in order to make a country 'eternally happy', one doesn't have to evolve an expensive symptom like Transcendence to severely cripple the cure effort and making the humans to submit to happiness. In fact, there is no such symptom on this scenario. Instead, you need only evolve Festive Tendrils and fully infect a country, plus a few symptoms that boosts happiness.
  • The Gift Planes also have a stronger effect than the normal Neurax Worm's Trojan Planes, able to infect millions upon arrival in target country.


  • Closed ports and land borders means spreading disease naturally prove to be more challenging, which can be countered using the Digital Elf symptom and the symptoms after it, or the gene Suppression, allowing closed land borders to be bypassed.
  • The lack of anti-cure traits makes it much harder to slow down the cure progress. Aridity will also be a serious problem if you don't evolve at least the Cracker Cocoon transmission.


  • The most noticeable difference between this scenario and normal Neurax Worm gameplay is that there are no natural disasters, no lethal symptoms, and no parallel to the Trojan Destroyer, meaning that there are no deaths in this scenario.
  • A noticeable trait of the Santa's Little Helper scenario is that if all symptoms are evolved, they form a shape resembling a typical six-point snowflake, another reference to the theme.
  • When the scenario ends successfully, a unique message pops up. Instead of saying [Disease Name] has eradicated all life on earth, it says that it brought happiness to all humans. Certain scenarios like the Frozen Virus also features unique end-game messages.
    • This is the only time that the Neurax Worm has a fixed ending.
  • The Lethality meter is kept, though it never increases.
  • The hat-wearing Neurax Worm has become somewhat of an icon for the company. Ndemic's Twitter often uses an ornament of it in their pictures, given the name "Neurie".



  1. "Mutation 1.10 is out now - The Santa's Little Helper Update!" (December 17, 2014). Ndemic Creations Retrieved on August 15, 2021.
Scenarios in Plague Inc.
Diseases Scenario black death.png Black DeathFrozen Virus Scenario Logo.png Frozen VirusScenario mad cow disease.png Mad Cow DiseaseScenario nipah virus.png Nipah Virus
Scenario smallpox.png SmallpoxScenario swine flu.png Swine Flu
World Changes Scenario global health.png Created EqualScenario flight club.png Flight ClubScenario global warming.png Global WarmingScenario develop this.png Golden Age
Scenario global cooling.png Ice AgeScenario opposites world.png Mirror EarthScenario ocean piracy.png Pirate PlagueScenario financial meltdown.png Sovereign Default
Scenario shut down.png Shut Down EverythingScenario volcanic ash.png Volcanic AshScenario who cares.png Who Cares
Scenario where is everyone.png Where Is Everyone?
Other Scenario artificial organs.png Artificial OrgansScenario fake news.png Fake NewsLittle helper.png Santa's Little HelperScenario science denial.png Science Denial
Teleportation.png TeleportationScenario ubg.png Ultimate Board GamesScenario unknown origin.png Unknown Origin
Scenario xenophobia.png Xenophobia
Removed Scenario aids.png AIDS