They are small, spider like creatures that crawl down the throats of humans to take over their bodies.

Individuals infected by swarmers still look human, presumably allowing swarmers to fool new potential victims.

Infectors are Necromorphs that resemble a mix between a bat and an insect.

They use their mutated proboscis to inject infectious fluids inside corpses to create new necromorphs.

They are mutated corpses, reshaped into horrific new forms by an extraterrestrial infection. They are aggressive creatures that seek to acquire more bodies to infect and spread the Corruption.