Avipoxvirus, a member of poxviridae family, only affects birds. The Poxviridae family of virus can cause the victim organism to have poxes as a symptom. They generally have large genomes. Other examples include smallpox and monkeypox. Although slow to spread it can cause symptoms like pustules full of pus lining the skin and diphtheria-like symptoms. It can be transmitted to humans by close contact with infected birds or by drinking liquids that were in contact with infected birds. It can also be transmitted by mosquitoes.

Brick shaped and measuring 200 nanometers in diameter the Avipoxvirus is much larger than the standard virus which is normally around 60 nanometers. It can also withstand extreme dryness unlike other viruses and can therefore spread on dust particles.

The virus has a high mortality rate in birds similar to poxviruses in humans. Other symptoms include difficulty breathing, eating, drinking, and lesions on non-feathered parts of the body. Another symptom is sacs or blisters filled with bloody fluid. The mortality rate is highest amongst upland gamebirds like songbirds, marine birds, seagulls, parrots, and some raptors. Generally if an infected bird lives long enough to have offspring the child will usually have brain damage.