Persistence of Avian Influenza Viruses in Various Artificially Frozen Environmental Water Types

Abstract

Background. This study investigates the viable persistence of avian influenza viruses (AIVs) in various types of artificially frozen environmental water and evaluates the feasibility of similar occurrence taking place in nature, and allowing for prolonged abiotic virus survival, with subsequent biotic viral recirculation. Methods. Fresh, brackish, and salty water, taken in Japan from aquatic biotopes regularly visited by migratory waterfowl, were seeded with AIVs. We monthly monitored the viability of the seeded viruses in the frozen state at −20°C and −30°C, for 12 months. We also monitored virus viability following repeatedly induced freezing and thawing. Results. The viruses exhibited considerable viable persistence all along that period of time, as well as during freezing-thawing cycles. Appreciable, yet noncrucial variances were observed in relation to some of the parameters examined. Conclusions. As typical waterborne pathogens of numerous northerly aquatic birds, AIVs are innately adapted to both the body temperature of their hosts (40°C to 42°C) and, presumably, to subzero temperatures of frozen lakes (down to −54°C in parts of Siberia) occupied and virus-seeded by subclinically infected birds, prior to freezing. Marked cryostability of AIVs appears to be evident. Preservation in environmental ice has significant ecophylogenetic and epidemiological implications, potentially, and could account for various unexplained phenomena.

Local-Scale Diversity and Between-Year “Frozen Evolution” of Avian Influenza A Viruses in Nature

“…In addition, there is no consistent view on this phenomenon in the literature [13]–[16], [18], [19]. In a recent study Shoham and colleagues [36] have demonstrated the ability of productive year-to-year preservation of avian IAV in arctic and sub-arctic ice which indicates that the frozen evolution evidently might operate in nature. However, we observed this phenomenon in the temperate zone.…”

Survival of Viruses in Water

“…As an example, the survival of poliovirus in water was historically extensively studied [16][17][18][19] before the number of studies declined in recent years in parallel with the eradication of the disease worldwide. On the other hand, there has been an increase in respiratory diseases linked to viruses carried by waterfowl, such as influenza [1,20,21], and studies on these viruses have been increasingly numerous. Likewise, following the terrorist threats of the early 2000s, more studies have been dedicated to potential biowarfare agents [6,22].…”

“…Obviously, heating will kill viruses within minutes [20,29]. Freezing temperatures allow viruses to remain stable for several months at least, although an initial decrease may be observed in the first days [1].…”

“…Influenza viruses, which have a lipid envelope, have been shown to survive well when exposed to freezing and thawing cycles: the envelope of some viruses solidifies from an oily substance to a hardened gel when the temperature decreases [1]. If viruses are able to survive freezing temperatures, ice may offer them protection from the environment, such as a reduced penetration of UV.…”

Efficacy of scallop shell powders and slaked lime for inactivating avian influenza virus under harsh conditions

“…They can survive for a long time in the environment, especially in water [1,19], and they exhibit prolonged viability at low environmental temperatures [26]. They are stable at a slightly basic pH (7.4-8.2) [2] and are considered to be sensitive to acidic or very alkaline conditions [18,23,25,32].…”