Avian influenza virus in water: Infectivity is dependent on pH, salinity and temperature

Wild birds in the Orders Anseriformes and Charadrifformes are the natural reservoir for avian influenza (AI) viruses. Transmission within these aquatic bird populations occurs through an indirect fecal-oral route involving contaminated water on shared aquatic habitats. In order to better understand the influence that aquatic environments exert on AI transmission and maintenance in the wild-bird reservoir system, we determined the duration of persistence for 12 wild-bird origin AI viruses under natural ranges of pH, salinity, and temperature. Viral persistence was measured using a laboratory-based distilled water model system. The AI viruses varied in their response to each of the examined variables, but, generally, the viruses were most stable at a slightly basic pH (7.4-8.2), low temperatures (<17 degrees C) and fresh to brackish salinities (0-20,000 parts per million (ppm)). Alternatively, the AI viruses had a much shorter duration of persistence in acidic conditions (pH < 6.6), warmer temperatures (>32 degrees C), and high salinity (>25,000 ppm). The results of this research suggest that the pH, temperature, and salinity in natural aquatic habitats can influence the ability of AI viruses to remain infective within these environments. Furthermore, these results provide insight into chemical and physical properties of water that could enhance or restrict AI virus transmission on an aquatic bird habitat. (C) 2008 Elsevier B.V. All rights reserved.