Persistence of H5 and H7 Avian Influenza Viruses in Water

TLDR

Fecal–oral transmission of avian influenza viruses via contaminated water is a known route in wild waterfowl, yet little is understood about how long the viruses persist in this medium. This study provides initial data on the persistence of low‑pathogenic H5 and H7 AIVs in water and evaluates the persistence of two highly pathogenic H5N1 strains from Asia to assess their potential environmental transmission. Viruses were tested at 17 °C and 28 °C across salinities of 0, 15, and 30 ppt. Wild‑type H5 and H7 AIVs remain infectious for extended periods, with persistence inversely related to temperature and salinity and salinity effects more pronounced at lower temperatures, whereas the two HPAI H5N1 strains persisted less than the wild‑type viruses.

Abstract

Although fecal–oral transmission of avian influenza viruses (AIV) via contaminated water represents a recognized mechanism for transmission within wild waterfowl populations, little is known about viral persistence in this medium. In order to provide initial data on persistence of H5 and H7 AIVs in water, we evaluated eight wild-type low-pathogenicity H5 and H7 AIVs isolated from species representing the two major influenza reservoirs (Anseriformes and Charadriiformes). In addition, the persistence of two highly pathogenic avian influenza (HPAI) H5N1 viruses from Asia was examined to provide some insight into the potential for these viruses to be transmitted and maintained in the environments of wild bird populations. Viruses were tested at two temperatures (17 C and 28 C) and three salinity levels (0, 15, and 30 parts per thousand sea salt). The wild-type H5 and H7 AIV persistence data to date indicate the following: 1) that H5 and H7 AIVs can persist for extended periods of time in water, with a duration of infectivity comparable to AIVs of other subtypes; 2) that the persistence of H5 and H7 AIVs is inversely proportional to temperature and salinity of water; and 3) that a significant interaction exists between the effects of temperature and salinity on the persistence of AIV, with the effect of salinity more prominent at lower temperatures. Results from the two HPAI H5N1 viruses from Asia indicate that these viruses did not persist as long as the wild-type AIVs.