Coinfection of wild ducks by influenza A viruses: distribution patterns and biological significance

Abstract

Coinfection of wild birds by influenza A viruses is thought to be an important mechanism for the diversification of viral phenotypes by generation of reassortants. However, it is not known whether coinfection is a random event or follows discernible patterns with biological significance. In the present study, conducted with viruses collected throughout 15 years from a wild-duck population in Alberta, Canada, we identified three discrete distributions of coinfections. In about one-third of the events, which involved subtypes of viruses that appear to be maintained in this duck reservoir, coinfection occurred at rates either close to or significantly lower than one would predict from rates of single-virus infection. Apparently, the better adapted an influenza A virus is to an avian population, the greater is its ability to prevent coinfections. Conversely, poorly adapted, nonmaintained viruses were significantly overrepresented as coinfectants. Rarely encountered subtypes appear to represent viruses whose chances of successfully infiltrating avian reservoirs are increased by coinfection. Mallards (Anas platyrhynchos) and pintails (A. acuta) were significantly more likely to be infected by a single influenza A virus than were the other species sampled, but no species was significantly more likely to be coinfected. These observations provide the first evidence of nonrandom coinfection of wild birds by influenza A viruses, suggesting that reassortment of these viruses in a natural population does not occur randomly. These results suggest that even though infections may occur in a species, all subtypes are not maintained by all avian species. They also suggest that specific influenza A virus subtypes are differentially adapted to different avian hosts and that the fact that a particular subtype is isolated from a particular avian species does not mean that the virus is maintained by that species.

Widespread Recombination, Reassortment, and Transmission of Unbalanced Compound Viral Genotypes in Natural Arenavirus Infections

“…Although natural infection by multiple arenaviruses has not been previously documented, this phenomenon has been reported for other viruses. For example, infection involving up to 3 influenza viruses has been documented in humans and wild birds [46,47]. And, up to 7 or 9 distinct genotypes of torque teno virus or papillomavirus have been identified in individual human samples [48][49][50].…”

Interspecies transmission and emergence of novel viruses: lessons from bats and birds

“…Birds are frequently infected by influenza A viruses. Reinfection during the same season with the same virus and coinfection with different viruses can occur [26]. Despite frequent infections, waterfowl usually remain asymptomatic even when infected by avian influenza viruses highly pathogenic in chicken [27].…”

Mathematical analysis of complex SIR model with coinfection and density dependence

“…Next, notice that the matrix B is stable if and only if its trace is negative and the determinant is positive. Because the first diagonal element in B is negative by (7) and the anti-diagonal elements are positive, the positivity of the determinant implies that…”