The Quaranfil and Johnston Atoll viruses are transmitted between vertebrates by ticks, resembling members of Thogotovirus, another genus of Orthomyxoviridae.

Zeller and colleagues suggested that they should be classified as arenaviruses,[4] but this was not accepted by the International Committee on Taxonomy of Viruses (ICTV).

[2] The virus particle is enveloped and spherical, ovoid or variable in shape, with a diameter generally in the range 80–120 nm.

The PA, PB1 and PB2 subunits of the trimeric RNA polymerase enzyme are encoded by the three largest segments (1–3), as in other orthomyxoviruses.

[9] Segment 7 of Wellfleet Bay virus encodes an additional protein of unknown function.

The most common arthropod hosts are species of soft-bodied (Argasidae family) ticks.

[9] In 2015, multiple new members of the genus were proposed based on RNA sequences obtained from mosquitos, flies, other insects, and the Neoscona spider.

[10] Aquatic birds that nest in colonies are the most common vertebrate hosts, including gannets, terns and herons.

[9] Cygnet River and Wellfleet Bay viruses have been associated with an often-fatal disease in farmed and wild duck species, with symptoms including diarrhoea and lethargy.

[7][9] Most genus members tested can infect mice under laboratory conditions; they cause severe pathology and are frequently lethal.

[2][3] Antibodies to the virus have been demonstrated in around 8% of people sampled in the area, although no further cases of symptomatic disease have been reported.

[16] Orthomyxoviridae-related viruses were found for the first time in insect hosts, such as Raphidioptera, Dermaptera, Archaeognatha, Neuroptera, Phasmatodea, Zygentoma, and Lepidoptera.