|Directed by:||Anthony Hemingway|
|Written by:||Karey Dornetto|
|Original air date:||October 28, 2010|
"Messianic Myths and Ancient Peoples"
"Aerodynamics of Gender"
"Epidemiology" is the sixth episode of the second season of the television series Community, and the 31st episode of the series overall. It aired in the United States on NBC on October 28, 2010 as a Halloween special.
Outside the Greendale library, Jeff greets Pierce, who is dressed as Captain Kirk for the annual Greendale Halloween party. The pair walk inside to enjoy the party, where all the songs being played are by the 1970s pop group ABBA. When Jeff confronts Dean Pelton, who is dressed as Lady Gaga, over the less than tasty food being served at the party, Pelton comments that he bought it at an army surplus store. Suddenly, Pierce begins sweating, and when Annie finds a doctor, it is discovered that Pierce is running a temperature of 102°F. While Troy and Abed attempt to court women with their Alien-inspired costumes, the nature of the mysterious sickness (which has by now been transmitted to several others at the party) takes a bizarre turn when Pierce takes a bite out of Star-Burns arm with his teeth.
It is discovered that the mysterious illness causes those affected to exhibit zombie]-like behavior and characteristics. The main characters (except Pierce) continue to enjoy the party, despite noticing that many of those attending the event appeared to be "high on drugs". Troy, who has by this time changed out of his science-fiction style costume and opted to dress as a "sexy Dracula" (that is, shirtless), calls Abed a nerd, hurting his feelings. Meanwhile, Dean Pelton leaves the library to head back to the school administration, as he believes food poisoning may have caused the mysterious illness. Pelton telephones the army surplus store where he purchased the food for the party, when he discovers that he had purchased something other than food instead. Pelton is transferred to an army special operations officer, who advises the Dean to quarantine those inside the library and wait for the army to arrive.
Back at the party, Leonard attacks a woman by biting her, and Troy and Abed realize their situation as in the middle of a zombie attack. The other uninfected still at the party realize what has happened and try to escape through the library's front door, only to find that the Dean has locked it from the outside, sealing all those inside the library with the infected zombies. Jeff and the group run to their group study room inside the library with Ben Chang and lock themselves inside. Rich (Greg Cromer), the doctor who helped Pierce earlier in the episode, asks anybody if they have been bitten, as if the group were to seal themselves inside with one of the infected, they would all be bitten. Nobody speaks up, and the doors are barricaded. Rich hypothesizes that should the temperature in the library be lowered, the fever could be broken. However, the thermostat is outside with the zombies. Rich also reveals that this type of fever could cause brain damage and death if left for more than six hours, meaning that by the time the army arrives, irreversible damage will have been done.
Rich begins to outline the disease's symptoms, and when he begins to exhibit some of them himself, it is clear that he had been bitten and did not disclose it to the others, thinking he was 'special'. Britta is also revealed to have been bitten. Chang throws a shoe at the pair in an attempt to knock them out, but ends up breaking the window behind the two, allowing the zombies to enter and bite Annie. Shirley and Chang escape to a nearby bathroom, where they end up kissing. Jeff, Troy and Abed get to the library's basement, where they are safe and spot a window. However, Jeff does not want to get his expensive suit dirty by going through the window, so opens a door instead, letting in the zombies from the other side. Jeff is bitten, but Troy manages to escape after Abed sacrifices himself to save him.
Outside, Troy meets with Dean Pelton and gets the keys from him, opening the door so he can get to the thermostat. Abed bites Troy, but while the virus is still incubating, Troy manages to reach the thermostat, then collapses to the ground. The air conditioning comes on and everyone is healed. The army arrives and is about to 'disinfect' the building, but discovers that those inside are uninfected, so allow them to live. Nobody can remember what happened, and the army gives the explanation that the party food and drink was drugged. The episode ends with Abed and Troy going to see Marmaduke.
In a ending tag scene, Troy receives a voicemail message from Chang before he became infected bragging that he and Shirley had 'hooked up'.
The episode was written by producer Karey Dornetto, her third writing credit on the series. It was directed by Anthony Hemingway, his first directing credit for a half-hour comedy series. He has previously directed episodes for The Wire, Battlestar Galactica, CSI: NY, and True Blood.
The following songs by the Swedish pop music group ABBA are featured throughout the episode: "Waterloo", "SOS", "Dancing Queen", "Gimme! Gimme! Gimme! (A Man After Midnight)", "Mamma Mia" and "Fernando".
This episode featured a special Halloween-themed opening credit sequence, unique to this episode. Series creator Dan Harmon later stated on his Twitter account that he paid for the changed opening credits himself, as it wasn't in the network's budget. 
In its original American broadcast, "Epidemiology" reached approximately 5.635 million households with a 2.4 rating/7% share in the 18-49 demographic. It was the least-watched non-reality component of NBC's Comedy Night Done Right for that evening (only The Apprentice, a reality show aired later that night, scored lower).
Alyssa Rosenberg from The Atlantic praised the episode, saying, "Community's on a roll with episodes torn straight from the reels of classic movies this season, and last night's Halloween episode lifted the show to new heights: this may have been the best half-hour of Community since "Contemporary American Poultry" and "Modern Warfare." Sean Gandert of Paste Magazine also found the episode to be one of the series' best, writing, "Community gets things so, so right. This is one of those special episodes that really pushed the boundaries of the show, and honestly, I even preferred it to "Modern Warfare"—this may be the best episode of the show so far."
- ↑ 'Community': Zombies + 'Wizard of Oz' = Awesome. October 29, 2010
- ↑ Community Review: "Epidemiology" (2.6). October 29, 2010
- "Epidemiology" at NBC.com