The film had its world premiere at the Sundance Film Festival on January 18, 2014 before being released on September 18, 2015 in a limited release and through video on demand by Lionsgate Premiere.
In the town of Ft. Chicken, Illinois, a fourth grade student at Ft. Chicken Elementary, Shelly Linker (Sunny May Allison), consumes a tainted black-dotted chicken nugget, this chicken nugget is contaminated with a mutant or extraterrestrial virus. Elsewhere, wannabe horror writer Clint Hadson (Elijah Wood) substitutes at Ft. Chicken Elementary, where he reunites with his former high school crush, Lucy McCormick, (Alison Pill), only to discover that she is already dating Wade Johnson (Rainn Wilson), the Physical Education teacher.
During class, Shelly, who had been experiencing numerous symptoms of strange wheezing and blisters on the face, brutally attacks her classmate, Patriot (Cooper Roth) after he tugs on one of her pigtails only to have it torn out of her scalp. She bites the skin off his cheek, infecting him with the virus; she also claws Clint, but he appears to show no symptoms. Though she tries to escape the school by digging her way out before she fully turns, Shelly turns feral and passes the virus to Dink (Miles Elliot), another bully and Patriot's friend by clawing his cheek. Dink, now infected with the virus, spreads the virus throughout the playground by scratching the rest of the children, resulting in the other children becoming infected and attacking the school staff; Mr. Pederson, Miss Nash, Mrs. Gordon, Nurse Rhonda, Vice Principal Simms and Mr. Henderson are all killed by the children. A police officer (Matt Jones) arrives at the scene to calm down the children, not realizing that they are beyond help, but has two fingers bitten off and is then mauled by Shelly as she escapes the playground and attacks him in his car. The few surviving staff members, consisting of Clint, Lucy, Wade, Tracy Lacey (Jack McBrayer), Rebbekah Halverson (Nasim Pedrad), Doug (Leigh Whannell), and Mrs. Birk (Tammie Baird), hide in the faculty lounge but are attacked by Patriot who tackles Mrs. Birk into a cupboard and mauls her to death (Tracy, apparently unaware of her real name, screams "Who is that lady?!" when this happens).
After escaping with a single uninfected student named Calvin (whom they found in the library studying for his test), the staff barricade themselves in the music room, but are discovered by Shelly, with more blisters on her face and retreats after a while. Wade notices Clint has been infected by Shelly and quarantines him and they see that Clint is severely vomiting, but Doug deduces that the virus doesn't affect him (or other adults) like it does the children. The staff decide to wait until the parents arrive to pick up the children, but this plan fails when Racer Dopkins, son of the local PTA president, infects his baby brother and that zombified baby attacks and kills his oblivious mother. They manage to rescue a teenager, Tamra (Morgan Lily) by pulling on Tracey's leg which has been grasped by the zombified kids, only to discover that she has also been infected, presenting a scratch.
The staff are attacked by the children again, and Wade kills Dink by beating him to death with a fire extinguisher. Doug extracts and analyzes his brain, which has turned black and rotten due to the decomposition effects caused by the virus. He concludes that the virus is only dangerous to the prepubescent (not going through puberty), which is why Clint and Tamra didn't turn feral as they had passed that stage. The staff and uninfected children unite with the local school janitor, Mr. Hitachi (Peter Kwong), but Calvin passes out due to diabetic shock. The group opts to send Clint through the ventilation system to gather a chocolate bar for Calvin, Wade's truck keys, and their cellphones. Lucy joins Clint and the two confess their feelings to each other while trapped in the library. Wade also apologizes for his behavior over a walky-talky. Though they discover the cellphones to have been destroyed by Patriot, they manage to secure a chocolate bar and bring Calvin out of diabetic shock. The group then reunites after Clint knocks out several children with drugs causing them to overdose, and utilizing various tools in the school as weapons, battle the children on the playground to eventually make their escape; however, Mr. Hitachi and Wade are seemingly killed by the children.
After killing a stowaway Patriot by crushing him against a tree, the group arrive in the nearby town of Danville, where they discover that it has been similarly overrun by the infected children. The group then learns that the viral infection has spread across the United States, with schools burning to the ground and reports of violence and destruction caused by children who have been infected with the virus, only to be ambushed by a horde of infected children. They barricade themselves inside a building and manage to retrieve a chicken nugget that is contaminated with the virus, which Doug will use to possibly make a vaccination for the virus. When the survivors attempt to leave the building, they stumble upon a funhouse play room with hoards of infected children, including Shelly. When the group is about to accept death, they hear a car backing in and the children stop to hear. Wade and Mr. Hitachi arrive and rescue the group. As Wade uses a massive beach ball to barricade the children, he sprays them with an unknown liquid. As he pulls out shades and a lighter, the liquid is gasoline and burns the kids in the funhouse. They then escape in crossing guard Rick's (Jorge Garcia) van, driving out of the town to "someplace kids don't wanna go". They are briefly pursued by a flaming Shelly, but she falls down and burns to death which eventually allows them to make their escape.
In the post-credits scene, Mr. Hitachi is shown sitting down, wielding a machete and finishes the frog and caterpillar story.
This ending was only shown in the DVD version and in the first showing in Sundance. After killing Patriot, they realize they are out of gas. The survivors venture on foot and eventually find a deserted Boy's Scout campsite. They enjoy themselves with no worries. Clint throws his novel in the fire and tells Lucy that he is not a writer and says he is actually a teacher, living in Ft. Chicken. Clint has a strong feeling of dread and tells the others to join him. They find a Boy's Scout leader's dead body, and the other infected children find them. Then you see infected Boy Scouts, led by Shelly, looking even worse than ever; her eyes look hollow black with more blisters covering her face. It's unknown what happened to everyone after the encounter.
Carnival music begins playing as three managers from an amusement park, a theater and a family fun center, respectively, get the chicken nugget boxes out of a truck carrying them. Because this ending was never shown in the final version, it is possible that the nuggets were also infected with the similar virus and is responsible for the outbreak.
The film was produced by Elijah Wood’s production company SpectreVision and Tove Christensen's company Glacier Films. Executive Producers include Leigh Whannell, Seth William Meier and Ian C. Brennan.
The filming began on July 15, 2013 in Los Angeles, California. Elijah Wood and Glacier Films produced the film. In September 2014, it was announced that they had filmed a new ending for the film which was paid for by Lionsgate. The new ending debuted at the Stanley Film Festival.
The film was scored by Kreng, and was released on September 18, 2015, by Milan Records, in digital download and physical CD formats.
On April 30, 2015, two teaser posters for the film were released. On May 20, 2015, the official trailer was released.
The film premiered on January 18, 2014 at the Egyptian Theatre in Park City, Utah during the 2014 Sundance Film Festival where it was selected to be featured in the "Park City at Midnight" program. The original planned release date in the United States was October 10, 2014. The film had its premiere opening night at the Stanley Film Festival on April 30, 2015. The film went onto screen at the Fantasia International Film Festival on July 17, 2015. The film had its Los Angeles premiere on September 3, 2015, at SpectreFest. It has also been selected to screen at the Sitges Film Festival on October 10, 2015.
The film was released in the US on September 18, 2015 in a limited release and through video on demand by Lionsgate Premiere. It debuted in 29 screens, where it placed 61st with $33,031. It saw a sharp 77% drop in its second weekend with a weekend gross of $7,545 from 20 screens, bringing its cumulative total to $55,749.
The film also opened in Russia the same weekend, where it came in seventh place with a weekend total of $113,995 from 695 screens (but with a low $164 per screen average).
The film opened in Malaysia on September 23. It debuted in eight place with a gross of $5,381 from 40 screens. The following day saw the movie released in both Malaysia ($22,321 from 40 screens), Thailand ($57,024 from 62 screens), and Ukraine ($6,109 from 44 screens)
As of September 30, 2015, the movie has a domestic gross of $55,749 and an international gross of $204,793 for a worldwide gross of $260,542.
Cooties received mixed reviews from film critics. It holds a 45% "Rotten" rating on review aggregator website Rotten Tomatoes, based on 38 reviews, with an average rating of 5.2/10. The critical consensus reads: "A horror-comedy without enough of either, Cooties is fatally content to skate by on its intriguingly oddball premise." On Metacritic, the film holds a rating of 49 out of 100, based on 21 critics, indicating "mixed or average reviews".
Although the film received mixed reviews, Kyle Burton of Indiewire.com gave the film a B+ and said "Gore can only go so far in the service of humor. Fortunately, the team behind Cooties—which includes Saw creator Leigh Whannell" and Glee creator Ian Brennan—manage to pit comedy and horror together in a satisfying package. With mainstay comedy faces, Cootie could reach a larger audience than other similar cultish work. It's the best play on the recent zombie craze, and while not as well-timed as Zombieland, it has the potential to match that movie's success with a wide enough release."
Peter Debruge of Variety.com gave the film a mixed review and said "Circle, circle, dot, dot. A schoolyard full of anklebiters develops a genuine taste for flesh in Cooties, an irreverent, off-color zom-com that seizes on the scourge of playgrounds everywhere when a spontaneous outbreak of brain-rotting, cannibalism-inducing germs erupts within a small-town elementary school. Told from the teachers’ p.o.v., this tongue-in-cheek midnight movie feels wrong in so many ways, asking a handful of irresponsible adults to bash and bludgeon their way through foaming packs of infected kids in order to save themselves. Acquired by Lionsgate at Sundance, the franchise-ready offering should benefit enormously from one of the distrib’s clever marketing campaigns."
The film was released direct-to-video in the United Kingdom on October 12, 2015. and in Germany on October 15, 2015.