Reduced airborne transmission of SARS-CoV-2 BA.1 Omicron virus in Syrian hamsters
Adrianus C. M. Boon, Tamarand L. Darling, Peter Halfmann, John Franks, Richard J. Webby, Dan H. Barouch, Julia R. Port, Vincent J. Munster, Michael Diamond, Yoshihiro Kawaoka
Abstract
Since the start of the COVID-19 pandemic, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has caused hundreds of millions of infections worldwide with more than 6.5 million confirmed deaths. SARS-CoV-2 is a respiratory virus that predominantly infects the epithelium of the upper and lower respiratory tract of human and animal hosts. Transmission of respiratory viruses between hosts can occur via direct contact, contact with infected surfaces, or via aerosolized particles [1]. Syrian hamsters are highly susceptible to SARS-CoV-2 infection and one of several animal hosts that have been naturally infected by this virus [2-14]. Transmission of SARS-CoV-2 from pet Syrian hamsters to humans has also been reported [2]. Currently, Syrian hamsters are the only rodent model in which airborne transmission can easily be tested [2,15]. Transmission of SARS-CoV-2 can be established by detection of viral RNA, RNA replication intermediates, viable infectious virus, or seroconversion, with the latter two metrics being the most stringent. Since January 2021, the National Institutes of Health SARS-CoV-2 Assessment of Variant Evolution (SAVE) initiative has evaluated the transmission potential of SARS-CoV-2 variants in Syrian hamsters [16]. Several SAVE-affiliated laboratories, using variable exposure times (4 to 48 hours), inoculum amounts (10 3 to 10 5 infectious units), and experimental designs, observed airborne transmission of SARS-CoV-2 (strain Wuhan-1 or WA1/20202) to nearly 100% of the contact animals. Similar results were obtained with the B.1.1.7 (Alpha), B.1.351 (Beta), and B.1.617 (Delta) variants of SARS-CoV-2 [15,17,18]. Airborne transmission was associated with high levels of viral RNA and infectious virus in respiratory tissues of the contact animal, and when tested, seroconversion (Fig 1). Certain amino acid mutations (D614G and N501Y) found in the receptor-binding domain of the spike protein of many SARS-CoV-2 variants improved airborne transmission of SARS-CoV-2 in hamsters [19-22]. Late in 2021,