Ten years after the pandemic of the deadly Rise of the Planet of the Apes, later called the Simian Flu, the worldwide human population was drastically reduced, with only about one in 500 genetically immune to the virus. Meanwhile, the apes, under the Common chimpanzee List of Planet of the Apes characters#Caesar, all bestowed with Genetic engineering Intelligence amplification by the virus, have long established a colony in the Muir Woods National Monument near San Francisco.