Oleavirus, 923-926, 932-934

Omegatetravirus, 757, 760-763

Ophiovirus, 36, 39, 627-630

Orbivirus, 395-398, 408-421

Orthohepadnavirus, 325-332

Orthomyxoviridae, 36, 39, 585-596, 620

Orthopoxvirus, 139, 143-144, 155

Orthoreovirus, 395-407

Oryzavirus, 395-398, 469-475

Ourmiavirus, 37, 40, 935-938