Developing Methods for Efficient Norovirus Recovery from Carpets

Introduction: Human Noroviruses (HuNoV) are a leading cause of acute gastroenteritis worldwide. HuNoV can persist in the environment making preventing HuNoV infections and controlling outbreaks extremely challenging. Epidemiological evidence suggests that soft surfaces, such as carpets, may be a relevant source of HuNoV due to ineffective and inadequate soft surface disinfection strategies. 

Purpose: The aim of this study was to develop a viral recovery method in order to adequately assess disinfectants against HuNoV on carpets. 

Methods: Shaved wool carpet fibers were packed into a cylindrical column and the electrokinetic potential (zeta potential) was measured with an Anton Paar SurPASS machine. Wool carpet fibers (0.1 g) were inoculated with HuNoV surrogates, feline calicivirus (FCV) strain F9 and murine norovirus (MNV) strain 1, and sampled at 0, 6, 12, 24, and 48 h. The recovery of MNV and FCV was assessed with 4 different elution buffers (DI water, PBS+Tween 80, PBS+Tween 20, Butterfield buffer) using a mini spin column method. The elution buffers were assessed based on percent recovery of HuNoV surrogates.

Results: Electrokinetic potential measurements indicated wool fibers become increasingly negative when saturated with higher pH solutions (- 56 mV at pH 7.7). The recovery efficiency of MNV from wool fibers was ca. 100% (5.8 log) at 0 h and 13.69% (4.9 log) at 48 h. FCV demonstrated a similar recovery 12.0% (5.1 log) at 48 h.  Among the elution buffers, viral recovery rates were not significantly different (P > 0.05). 

Significance: This was the first study to attempt to develop a method for recovering viruses from carpet surfaces. Recovery with a mini spin column, although not sensitive enough to assess elution buffer effectiveness, demonstrates superior viral recovery compared to previous soft surface recovery methods, which may lead to more accurate inactivation studies.