Phycodnaviridae is a family of large (100–560kb) double stranded DNA (dsDNA) viruses that infect marine or freshwater eukaryotic algae. Viruses within this family are similar morphologically and possess an icosohedral capsid (polyhedron with 20 faces). There are currently 33 species in this family, divided among 6 genera. This family belongs to a super-group of large viruses known as nucleocytoplasmic large DNA viruses (NCLDVs). Recently, there is evidence that specific strains of Phycodnaviridae may infect humans rather than just algal species, as was previously believed. Most genera under this family enter the cell of the host by cell receptor endocytosis and replicate in the nucleus. Phycodnaviridae play important ecological roles by regulating the growth and productivity of their algal hosts. Algal species such Heterosigma akashiwo and the genus Chrysochromulina can form dense blooms which can be damaging to fisheries, resulting in losses in the aquaculture industry. "Heterosigma akashiwo virus" (HaV) has been suggested for use as a microbial agent to prevent the recurrence of toxic red tides produced by this algal species. Furthermore, Phycodnaviridae cause death and lysis of freshwater and marine algal species, liberating organic carbon, nitrogen and phosphorus into the water, providing nutrients for the microbial loop.
