Experimental co-infection of calves with SARS-CoV-2 Delta and Omicron variants of concern oleh Konner Cool, Natasha N. Gaudreault, Jessie D. Trujillo, Igor Morozov, Chester D. McDowell, Dashzeveg Bold, Taeyong Kwon, Velmurugan Balaraman, Patricia Assato, Daniel W. Madden, Emily Mantlo, Jayme Souza-Neto, Franco Matias-Ferreyra, Jaime Retallick, Gagandeep Singh, Michael Schotsaert, Mariano Carossino, Udeni B. R. Balasuriya, William C. Wilson, Roman M. Pogranichniy, Adolfo García-Sastre, Juergen A. Richt