[2] The Ranaviruses, like the Megalocytiviruses, are an emerging group of closely related dsDNA viruses which cause systemic infections in a wide variety of wild and cultured fresh and saltwater fishes.

[3][4] The impact of Ranaviruses on amphibian populations has been compared to the chytrid fungus Batrachochytrium dendrobatidis, the causative agent of chytridiomycosis.

[13] The genus contains the following species:[24] The family Iridoviridae is divided into seven genera which include Chloriridovirus, Iridovirus, Lymphocystivirus, Megalocytivirus, and Ranavirus.

[29] There is evidence that ranavirus infections target macrophages as a mechanism for gaining entry to cells.

[31] Transmission of ranaviruses is thought to occur by multiple routes, including contaminated soil, direct contact, waterborne exposure, and ingestion of infected tissues during predation, necrophagy or cannibalism.

[11][32] Ranaviruses are relatively stable in aquatic environments, persisting several weeks or longer outside a host organism.

[36] Ranaviruses grow in vitro between 8-30 °C, however for most isolates, warmer temperature result in faster viral replication.

[36] A combination of this optimal growth temperature along with shifts in larval amphibian susceptibility result in seasonal outbreak events most often observed during warm summer months.

This decrease in immune function and warmer environmental temperatures allows for greater viral replication and cellular damage to occur.