Comparison of Surface Sampling Methods for Virus Recovery from Fomites

Abstract

The role of fomites in infectious disease transmission relative to other exposure routes is difficult to discern due, in part, to the lack of information on the level and distribution of virus contamination on surfaces. Comparisons of studies intending to fill this gap are difficult because multiple different sampling methods are employed and authors rarely report their method's lower limit of detection. In the present study, we compare a subset of sampling methods identified from a literature review to demonstrate that sampling method significantly influences study outcomes. We then compare a subset of methods identified from the review to determine the most efficient methods for recovering virus from surfaces in a laboratory trial using MS2 bacteriophage as a model virus. Recoveries of infective MS2 and MS2 RNA are determined using both a plaque assay and quantitative reverse transcription-PCR, respectively. We conclude that the method that most effectively recovers virus from nonporous fomites uses polyester-tipped swabs prewetted in either one-quarterstrength Ringer's solution or saline solution. This method recovers a median fraction for infective MS2 of 0.40 and for MS2 RNA of 0.07. Use of the proposed method for virus recovery in future fomite sampling studies would provide opportunities to compare findings across multiple studies.Preclusion of infection is the most effective method to combat the respiratory and gastrointestinal diseases that cause over 6 million annual deaths worldwide (12, 59). Successful interventions to reduce disease burden include hand and environmental hygiene (9, 76), but the impact of these interventions is difficult to quantify, as the importance of contact with contaminated surfaces, or fomites, relative to other transmission routes is uncertain (17,62).Evidence of the importance of fomites comes from both laboratory and field studies. Laboratory studies have demonstrated that the handling of either artificially or naturally contaminated fomites by susceptible hosts indoors results in subsequent infection (41, 43). Additionally, virus can be transferred between hands and fomites on contact and survive on fomites for hours or days (1,8,72). As such, it is not surprising that fomites, such as carpets (29, 65), towels, and medication cart items (60) have been implicated as the primary cause of multiple outbreaks. Environmental hygiene intended to mitigate fomite-mediated transmission has been shown to significantly reduce illness-related absences in classrooms (18). Despite this evidence, questions remain regarding both the efficacy of fomite-mediated transmission relative to other exposure routes (5, 46) and the likelihood of virus transfer from fomites to hosts (66).To better understand the role of fomites in disease transmission, characterization of the level and distribution of virus on surfaces is required. Surface contamination is most often described by the positivity rate, defined as the fraction of total samples collected on which the organism is detectable (19). However,...

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