A genus of giant viruses first described in 2013. They infect amoebas and measure roughly 1×0.5 µm, making them larger than many bacteria, and they have unusually large genomes, of 1.9 and 2.5 million bases, with many unique genes of unknown function. The viral particles enter the host amoeba via phagocytic vacuoles and fuse with the vacuole membrane. Like other giant viruses, pandoraviruses are regarded as nucleocytoplasmic large DNA viruses, and may represent forms that originally evolved from cellular organisms.