[7] The discovery of Pandoraviruses by a team of French scientists, led by husband and wife Jean-Michel Claverie and Chantal Abergel, was announced in a report in the journal Science in July 2013.

[5] Other scientists had previously observed the pandoravirus particles, but owing to their enormous size they were not expected to be viruses.

[5] Patrick Scheid, a parasitologist from the Central Institute of the Bundeswehr Medical Service in Koblenz, Germany, found one in 2008, in an amoeba living in the contact lens of a woman with keratitis.

Unlike in other cases with such giant viruses, the large particles within Acanthamoeba were not mistaken for bacteria.

[9] Megavirus, discovered in seawater off the coast of Chile in 2011, has a genome size of approximately 1.2 megabases.

[10] The prior discovery of these viruses prompted a search for other types of large amoeba-infecting viruses, which led to the finding of two species; Pandoravirus salinus, found in seawater taken from the coast of Chile, with a genome size of ~2.5 megabases, and Pandoravirus dulcis, found in a shallow freshwater pond in La Trobe University, Melbourne, Australia, with a 1.9 megabase genome.

Under the microscope, scientists observed the virus enter the amoeba through fusion with membrane vacuoles, and integrate their DNA into the host cells.

Viral infection and lysis can influence community structure, as well as the transfer of matter and energy in aquatic ecosystems.

[15] Approximately 93% of Pandoravirus genes are not known from any other microbes,[16] suggesting that they belong to an as of yet undescribed "fourth domain" aside from Bacteria, Archaea, and Eukaryotes.