Flu (Korean: 감기; RR: Gamgi; alternatively titled The Flu) is a 2013 South Korean medical disaster film written and directed by Kim Sung-su, about an outbreak of a deadly strain of H5N1 that kills its victims within 36 hours, throwing the district of Bundang in Seongnam, which has a population of nearly half a million people, into chaos.

At the Contagion Center in Bundang, Dr. Kim In-hae is reprimanded for losing important data when her car fell down a mine shaft the previous day.

Called in to help, In-hae finds the cellphone video and theorizes that conditions in the shipping container allowed the virus to mutate.

While disparaging the need for a quarantine, administrators and politicians are confronted with a catastrophic situation as people collapse in the street, including drivers who cause a series of violent crashes.

Politicians and research staff evacuate to Seoul and brief the Prime Minister, who makes a public announcement that worsens the panic in Bundang.

In-hae gets them passage to Seoul, but Ji-goo refuses to abandon his duties and works with Kyung-ub to free those trapped in the store.

Those displaying symptoms are further isolated in an infected quarantine zone (IQZ) beneath the stadium to receive medical treatment, though In-hae knows they have no cure.

In-hae's proposal to directly inject his antibodies into a patient is overruled, but she secretly begins a transfusion to Mi-reu, whose condition has worsened.

There is unease in the camp due to a communications blackout, difficult living conditions, confrontations with gasmask-wearing guards, sporadic gunfire meant to keep birds from spreading the disease, and rumours that infected people are being killed.

In-hae and the medical staff flee the mob, but Byung-ki kills Monssai in a suicidal attack to avenge his brother's death.