Change in Concentrations of Human Norovirus and Male-Specific Coliphage under Various Temperatures, Salinities, andpH Levels in Seawater

摘要

Pre- or post-harvest processing is required to mitigate the risk of norovirus infection mediated by shellfish or seafood. We investigated the environmental resistance of human norovirus (HuNoV) under various conditions of temperature, salinity, and pHin seawater. Male-specific coliphage (MSC) was as the reference virus for all tests. At 4°C, HuNoV GII4 spiked into seawater was continually detected by RT-PCR for 35 days, regardless of salinity or pH level. It maintained nearly stable concentrations,meaning HuNoV can sustain a viral population in seawater long enough to be accumulated by shellfish and other filter feeders during winter. MSC was also stable at 4°C although viral infectivity dropped sharply after 28 days. The effects of salinity andpH on MSC were indistinct. At 25 °C the detectable period of HuNoV GII4 by RT-PCR in seawater decreased to about one-third or half of the period at 4°C- High salinity (32 psu) and alkaline pH (8.5) were also unfavorable for sustaining HuNoV abundanceat 25 °C in seawater. The resistance patterns of MSC to high temperature, high salinity, and alkaline pH were more dramatic and viral infectivity decreased over time, almost in direct proportion to experimental days. MSC was undetectable after 12 days under all salinities and pH levels at 25 °C-