Handwashing and Detergent Treatment Greatly Reduce SARS-CoV-2 Viral Load on Halloween Candy Handled by COVID-19 Patients

Abstract

Due to the COVID-19 pandemic and potential public health implications, we are publishing this peer-reviewed manuscript in its accepted form. The final, copyedited version of the paper will be available at a later date. Although SARS-CoV-2 is primarily transmitted by respiratory droplets and aerosols, transmission by fomites remains plausible. During Halloween, a major event for children in numerous countries, SARS-CoV-2 transmission risk via candy fomites worries many parents. To address this concern, we enrolled 10 recently diagnosed asymptomatic or mildly/moderately symptomatic COVID-19 patients to handle typical Halloween candy (pieces individually wrapped) under three conditions: normal handling with unwashed hands, deliberate coughing and extensive touching, and normal handling following handwashing. We then used a factorial design to subject the candies to two post-handling treatments: no washing (untreated) and household dishwashing detergent. We measured SARS-CoV-2 load by RT-qPCR and LAMP. From the candies not washed post-handling, we detected SARS-CoV-2 on 60% of candies that were deliberately coughed on, 60% of candies normally handled with unwashed hands, but only 10% of candies handled after hand washing. We found that treating candy with dishwashing detergent reduced SARS-CoV-2 load by 62.1% in comparison to untreated candy. Taken together, these results suggest that although the risk of transmission of SARS-CoV-2 by fomites is low even from known COVID-19 patients, viral RNA load can be reduced to near zero by the combination of handwashing by the infected patient and ≥1 minute detergent treatment after collection. We also found that the inexpensive and fast LAMP protocol was more than 80% concordant with RT-qPCR. IMPORTANCE The COVID-19 pandemic is leading to important tradeoffs between risk of SARS-CoV-2 transmission and mental health due to deprivation from normal activities, with these impacts being especially profound in children. Due to the ongoing pandemic, Halloween activities will be curtailed as a result of the concern that candy from strangers might act as fomites. Here we demonstrate that these risks can be mitigated by ensuring that prior to handling candy, the candy giver washes their hands, and by washing collected candy with household dishwashing detergent. Even in the most extreme case, with candy deliberately coughed on by known COVID-19 patients, viral load was reduced dramatically after washing with household detergent. We conclude that with reasonable precautions, even if followed only by either the candy giver or the candy recipient, the risk of viral transmission by this route is very low.

Swabbing the Urban Environment - A Pipeline for Sampling and Detection of SARS-CoV-2 From Environmental Reservoirs

“…Moreover, RT-qPCR techniques-even those formulated to resist inhibitors-were sensitive to substances contained in the environmental samples collected by a pilot cohort of citizen scientists, even after the use of other common strategies to reduce inhibitor competition for enzyme binding 49 . These findings are corroborated by a recent study that compared both methods to detect SARS-CoV-2 on swab samples from candy handled by COVID-19 patients and found over 83% result concordance, with 25% lower inhibition in samples analyzed by RT-LAMP 15 . Furthermore, the GITC-chloroform crude extraction, coupled with RT-LAMP, reduced the cost of reagents and supplies by 42% compared to RNA kit extraction and RT-qPCR (Table of Materials…”

“…The detection of SARS-CoV-2 RNA using RT-LAMP has been demonstrated to be over 83% concordant to using RT-qPCR. Furthermore, RT-LAMP resulted in 25% reduction in inconclusive results compared to RT-qPCR 15 .…”

“…Air and surface samples from hospitals and mass-transit systems have tested positive for SARS-CoV-2 and other coronaviruses 8 , 10 , 11 , 12 , 13 , 14 . A study performed on the outer packaging of Halloween candy handled by asymptomatic and moderate/mildly symptomatic COVID-19 patients, concluded that the combination of hand washing by the handler and washing of the candy with hand soap reduced SARS-CoV-2 RNA to below threshold levels 15 .…”

SARS-CoV-2 Transmission Risk from sports Equipment (STRIKE)

“…Exponential viral decay was predicted from the linear regression models for all surfaces tested, indicated by a straight line of decay on the log 10 viral PFU scale (Fig. 6).…”

“…8 This is thought to be from the spread of respiratory droplets via breathing, sneezing and coughing, 9 and the transfer of SARS-CoV-2 to objects from the hands of patients has been documented. 10 The minimum infectious dose of SARS-CoV-2 is currently unknown, 7 which makes quantifying the required viral load for transmission difficult.…”