SARS-CoV-2 RNA stability in dry swabs for longer storage and transport at different temperatures

Alfaro-Núñez, Alonzo; Crone, Stephanie; Mortensen, Shila; Rosenstierne, Maiken Worsøe; Fomsgaard, Anders; Marving, Ellinor; Nielsen, Sofie Holdflod; Jørgensen, Michelle Grace Pinto; Polacek, Charlotta; Cohen, Arieh S; Nielsen, Claus

During the current COVID-19 pandemic, different methods have been used to evaluate patients with suspected SARS-CoV-2 infection. In this study, we experimentally evaluate the ability of spiked saliva-moist swabs and spiked swabs without any transport medium to retain SARS-CoV-2 for storage and transport at different environmental settings during different incubation time periods. Our results show that at ambient temperature of 20°C, SARS-CoV-2 RNA remains stable for up to 9 days allowing a long-time span for transport and storage without compromising clinical results. Additionally, this study demonstrates that saliva-moist swabs can also be stored at -20°C and +4°C for up to 26 days without affecting RT-qPCR results. Our data are relevant for low-and middle-income countries, which have limited access to rapid refrigerated transport and storage of samples representing an economical alternative. Finally, our study demonstrates the practical and economic advantage of using swabs without transport medium.