The host's own tissue fights back, but it doesn't take sides. Every organ has its own hazards, and they hurt immune cells as much as you or more, so the trick is to lure the immune system into them. Organ hazards unlock for your whole save when any virus reaches level 8, and the organ where they first appear has them in every fight room.
Glowing nerve fibres in the walls. Linger on one and it fires a reflex that flings you and every cell nearby away from the wall.
Found in about 45% of Nasal Passage fight rooms, 40% of Lungs fight rooms, and every boss room in those two organs
Stand on one for about half a second and it fires: a Sneeze Reflex in the nose, or a bigger Cough Reflex in the lungs
The blast hurts every cell caught in it (24 in the nose, 30 in the lungs) and you a little (8 / 10)
Set it off yourself and Detection rises. Shoot near it and it fires at once, and the host blames the cells
Cells flung into an abyss die. It recharges after 7 s
From the Codex
Sensory nerve endings line the airways. When something irritates them, the trigeminal nerve in the nose triggers a sneeze and the vagus nerve in the lungs triggers a cough, blasting irritants (and viruses) out at high speed.
Fun fact: A sneeze can launch droplets at over 30 m/s and spread them several metres, which is exactly how flu hitches a ride to the next host.
A carpet of beating hairs that carries anything on it the way the arrows point: you, cells, everything.
In about 35% of fight rooms, 1–2 carpets per room
Dash to cross against the flow
Cells swept into a pit die ("SWEPT AWAY!")
From the Codex
Airway cells are covered in cilia, tiny hairs that beat about 15 times a second in coordinated waves, sweeping mucus and trapped microbes up and out (the mucociliary escalator).
Fun fact: Smoking paralyses cilia, which is one reason smokers get more chest infections.
Solid discs drifting with the pulsing blood flow. They shove you around and soak up shots from both sides.
In about 60% of Bloodstream fight rooms, 4–6 at a time
They push you and ordinary cells out of the way
They block enemy shots as well as yours. Three of your shots burst one
A fresh one drifts in from upstream 5 s later
From the Codex
Red blood cells are the most common cells in the body, around 25 trillion of them, carrying oxygen in haemoglobin. Their dimpled disc shape lets them squeeze through capillaries.
Fun fact: Red blood cells have no nucleus, so most viruses can't infect them; malaria parasites can.
Pairs of neurons that fire an electric arc between them every few seconds after a flickering warning.
In about half of Brain fight rooms, 1–2 neuron pairs
The line flickers for 0.8 s, then the arc crackles for about half a second
The arc deals 10 damage to you but 40 to every cell it crosses
It fires every 4 s. Shoot a neuron to fire it early
From the Codex
Neurons talk at synapses with electrical spikes and chemical signals. Some viruses, like rabies and herpes, travel along neurons from synapse to synapse.
Fun fact: Rabies moves through nerves at a few centimetres a day toward the brain.
A rare glowing shaft in one of an organ's deeper fight rooms. Walk in and the current sweeps you into a freshly shuffled layout of the organ.
About a 15% chance per organ layout
Landing announces "SWEPT AWAY: the current carries you somewhere new"
You land with a moment of invulnerability, and hunting Killer T cells lose your trail
From the Codex
Viruses spread between organs through airways, blood and lymph: flu can move from the nose down into the lungs, and HIV travels through the blood to lymph nodes.
Fun fact: Inhaled droplets small enough can bypass the nose entirely and land deep in the lungs.
