CCR9 and COVID-19: Our concordant susceptibility profiles of the CC011 and CC074 parent mouse lines, as well as Ccr9- and Cxcr6-deficient mice infected with SARS-CoV MA15, SARS-CoV-2 MA10 or BtCoV HKU3-SRBD MA, demonstrate involvement of this locus in severe COVID-19 disease susceptibility across species and across different sarbecoviruses, as well as highlighting the utility of preemergence disease models.