In February 2024, while conducting surveillance for novel respiratory viruses, we
studied four beef cattle farms near Monterrey, Mexico. Nasal swabs were collected from sick and healthy beef cattle along with 3 h aerosol samples. None of the samples had molecular evidence of influenza A viruses. Three (8%) of thirty-six nasal swabs collected from the four farms and four (33.3%) of the twelve bioaerosol specimens had molecular evidence of influenza D virus. Five sick cow nasal swabs and one bioaerosol sample on a single farm had molecular evidence of rodent coronavirus-like (RCoV), an alphacoronavirus. Three (60%) of the five RCoV-positive cattle nasal swabs also had molecular evidence of influenza D. Attempts to isolate the RCoV in Vero-E6, LLC-MK2, MDBK, and L-2 cells were unsuccessful. However, we were able to assemble ~60% of the RCoV genome using next-generation sequencing. The six RCoV-positive samples clustered with RCoV strains identified in China in 2021. During the last 12 months, we have studied an estimated 478 dairy and beef cattle nasal swabs on 11 farms in the US and Mexico, and these RCoV detections are the first we have encountered. While feed contamination cannot be ruled out, given the propensity of CoVs to jump species and that we detected RCoV only in the noses of sick cows on this one farm, we are concerned that these findings could represent an isolated RCoVspillover event. With this report, we are alerting veterinarians and cattle farm owners of our observations that RCoV may be a new cause of bovine respiratory disease.