Avian pox is a mild to severe, slow developing disease of birds caused by an avipoxvirus and three common strains have been identified. The three strains are fowl pox virus, pigeon pox virus and canary pox virus. The strains vary in their virulence and have the ability to infect other avian species. However, many of the strains are group specific. Approximately sixty species of birds from 20 families have been diagnosed with avian pox. The strain seen in wild turkeys is the fowl pox virus.

Avian pox lesions (wart-like growths) occur on the unfeathered parts of the bird's body and, in some cases, the mouth, larynx, and/or trachea. 

Transmission of the avian pox virus can occur in a number of ways. The disease can be spread via mechanical vectors, primarily by species of mosquitoes (at least 10). Transmission occurs when the mosquito feeds on an infected bird that has a viremia (pox virus circulating in the blood) present or on virus-laden secretions from a pox lesion and then feeds on an uninfected bird. Mosquitoes can harbor and transmit the virus for a month or longer after feeding on an infected bird. Experimentally, stable flies have shown the capability of being able to transmit the pox virus.

Avian pox can also be transmitted by direct contact between infected and susceptible birds. The virus is transmitted through abraded or broken skin or the conjunctiva (mucous membrane covering the anterior surface of the eyeball). Indirect transmission of the pox virus can also occur via ingestion when food and water sources, feeders, perches, cages, or clothing are contaminated with virus-containing scabs shed from the lesions of an infected bird. The pox virus is highly resistant to drying and may survive months to years in the dried scabs. Indirect transmission can also occur via inhalation of pox virus infected dander, feather debris and air-borne particles.

Mosquitoes are probably responsible for transmission within local areas, while wild birds are responsible for outbreaks over greater distances.