Pinkeye is a virus that infected the town of South Park in the Season One episode, "Pinkeye". In the episode, it is a zombie virus. However, in real life, it is an infection that causes inflammation of the eye.
Background[]
The virus known as conjunctivitis or pink-eye is used, in name only, as a way to parody zombie horror films' explanations for why zombies exist. When Kenny McCormick dies, the morticians at the South Park Morgue accidentally reanimate his corpse by combining Limey Charles Worcestershire Sauce with Embalming Fluid, and a half eaten hot dog. He becomes the first person infected and turns the morticians into zombies by biting them.
The morticians go to see a doctor at the clinic. The doctor informs them their body temperature is 55 degrees, no pulse, no heartbeat, their eyes are all puffy and sticky. He misdiagnoses their condition as "pinkeye" and prescribes a topical cream and warns them not to touch their eyes.
On Halloween night the next day, almost everyone in town is now a zombie, even Chef. Kyle Broflovski saves the town by calling the Worcestershire Sauce hot line for help. The hotline tells Kyle that they must kill the original zombie to stop it from spreading. Kyle then saws Kenny in two with a chainsaw, which causes everyone previously infected to return to normal, effectively ending the Pinkeye Virus in the town of South Park.