Recovery optimization and survival of the human norovirus surrogates feline calicivirus and murine norovirus on carpet

Abstract

Carpets have been implicated in prolonged and reoccurring outbreaks of human noroviruses (HuNoV), the leading cause of acute gastroenteritis worldwide. Viral recovery from environmental surfaces, such as carpet, remains undeveloped. Our aim was to determine survival of HuNoV surrogates on an understudied environmental surface, carpet. First, we measured the zeta potential and absorption capacity of wool and nylon carpet fibers, we then developed a minispin column elution (MSC) method, and lastly we characterized the survival of HuNoV surrogates, feline calicivirus (FCV) and murine norovirus (MNV), over 60 days under 30 and 70% relative humidity (RH) on two types of carpet and one glass surface. Carpet surface charge was negative between relevant pH values (i.e., pH 7 to 9). In addition, wool could absorb approximately two times more liquid than nylon. The percent recovery efficiency obtained by the MSC method ranged from 4.34 to 20.89% and from 30.71 to 54.14% for FCV and MNV on carpet fibers, respectively, after desiccation. Overall, elution buffer type did not significantly affect recovery. Infectious FCV or MNV survived between < 1 and 15 or between 3 and 15 days, respectively. However, MNV survived longer under some conditions and at significantly (P < 0.05) higher titers compared to FCV. Albeit, surrogates followed similar survival trends, i.e., both survived longest on wool then nylon and glass, while 30% RH provided a more hospitable environment compared to 70% RH. Reverse transcription-quantitative PCR signals for both surrogates were detectable for the entire study, but FCV genomic copies experienced significantly higher reductions (< 3.80 log10 copies) on all surfaces compared to MNV (< 1.10 log10 copies).