Codex
The biology behind replication, mutation and immunity.
Coating a pathogen with antibodies or complement so phagocytes can grab and destroy it more easily.
In the game
The Plasma Cell's lock-on volley opsonizes you: you take 35% more damage for 5 seconds.
Fun fact: The word comes from Greek for "to prepare food": opsonins make microbes tastier to phagocytes.
Each infected cell releases new virions that go on to infect its neighbours, so an infection can grow exponentially.
In the game
Pandemic infects cells, burning them over time; Superspreader makes them pass it on.
Fun fact: A single flu-infected cell can release thousands of new virions within hours.
Appears inInfluenza AHalovirusThe EndingSkill TreePetri LabClass-Ability BonusesInfect Game ModePandemic Game ModeAudio & Presentation
A change in a genome's sequence. Most are harmless or harmful, and a few help the organism survive.
In the game
Glowing orbs mid-run let you pick 1 of 3 traits for the rest of the run.
Fun fact: Flu's RNA polymerase doesn't proofread, so it makes errors constantly.
Appears inTrade-off AltarsDrops & PickupsRun ModifiersModifier CombosLineage & GenerationsCombiningGear Mutations
Small mutations that gradually change a virus's surface proteins so antibodies recognise it less well.
In the game
Influenza's passive: your shot type changes every few seconds.
Fun fact: This is why the flu vaccine is updated almost every year.
Appears inInfluenza APetri Lab
An abrupt, major change in a flu virus, caused when two strains infect the same cell and swap RNA segments (reassortment).
In the game
Influenza's Shift ability: a burst of every mutation, then rapid fire.
Fun fact: Shifts have produced new pandemic strains, including those of 1957, 1968 and 2009.
Appears inInfluenza APetri LabGear StatsClass-Ability Bonuses
Immune cells exist in resting and activated states. Activated cells are bigger, multiply, produce more weapons and live longer; trained memory cells respond faster on a second encounter.
In the game
Any cell can spawn at a tier from white to red, like gear. Higher tiers are bigger, tougher and hit harder, and from blue up roll affixes (Swift, Armored, Regenerating, Vampiric, Volatile, Shielded, Splitting, Enraged). They drop much better loot.
Fun fact: An activated T cell can divide every 4 to 6 hours, turning one cell into thousands within days.
Appears inElite TiersElite AffixesRoom TraitsRun ModifiersGear SourcesEndless Boons & Curses
"Cell eating": a cell wraps its membrane around a particle or microbe, swallows it and digests it.
In the game
The Alveolar Macrophage's engulf attack.
Fun fact: A single macrophage can swallow more than 100 bacteria before it wears out.
Appears inThe Codex
The time between catching a virus and feeling sick. The virus is multiplying, but the body hasn't noticed yet, so there are no symptoms.
In the game
An extra life for this run. When you'd die, a stored incubation is spent: you go dormant, ordinary cells lose track of you (bosses, Killer T cells and rivals keep hunting), and you re-emerge somewhere safe. Get it from the rare Incubation Period trait (unlocks at generation 3) or a Dormant Virion drop.
Fun fact: Flu incubates for about 1–4 days, measles about 10–12, and rabies can take months; HIV's silent clinical latency can last 10 years.
Appears inDrops & PickupsExtra LivesRun ModifiersModifier Combos
A dormant state where a virus hides inside a cell without making new copies, invisible to the immune system.
In the game
Retrovirus's ability: go invisible for a few seconds, and hunters lose track of you.
Fun fact: Latent HIV reservoirs are the main reason the infection can't yet be cured.
Appears inRetrovirusTrade-off AltarsPetri Lab
A raised body temperature triggered by the immune system. It slows some pathogens and speeds up immune responses.
In the game
Immune Alert: rises over time and makes cells tougher and hit harder.
Fun fact: The fever and aches of the flu come mostly from your own immune response, not directly from the virus.
Appears inPetri LabHosts & GenomeEndless Game ModeEndless Boons & Curses
The slower, targeted immune response that learns the specific features of a pathogen and remembers them.
In the game
Lean on one shot type too much and cells start resisting it.
Fun fact: Vaccines work by training this system without the real disease.
Appears inAdaptive ImmunityThe HUDPetri LabRun ModifiersModifier Combos
