SARS-CoV-2 infections among animals in US zoological institutions resulted primarily from human-to-animal transmission without evidence of sustained evolution in animals (2020-2023).
Cristiano DJ, Varela KE, Anderson CE, Croft L, Crook E, Hanley C, Junge R, Montgomery D, Newland K, Rivera S, Rosenberg JF, Worden D, Yoshicedo J, Young S, Baker M, Beddo M, Carruthers M, Feldpausch A, Oltjen H, Tewari D, Rekant SI, Cleary S, Kalinich CC, Liew A, Behravesh CB, Ghai RR, · Journal of the American Veterinary Medical Association · 25 March 2026
Zoological animals infected with SARS-CoV-2 primarily from human exposure without sustained viral evolution.
This retrospective observational study examined SARS-CoV-2 infections in animals at US zoological institutions from 2020-2023. Researchers analyzed 170 confirmed positive animals across 13 species in 28 jurisdictions through voluntary national surveillance. Clinical presentation occurred in 72.4% of infected animals, with cough being the most common sign (60.0%). Known infected caretaker exposure accounted for 44.7% of transmission cases, establishing zoological facilities as high-risk environments for zoonotic spill-back. Twelve institutions with documented outbreaks showed increased biosecurity practice implementation post-outbreak (52.9 vs 48.7 practices from baseline). Genomic analysis revealed no evidence of sustained viral evolution in zoo animal populations; instead, sequences matched variants circulating in the human population contemporaneously. The findings underscore the importance of enhanced biosecurity measures in zoological settings to protect vulnerable animal populations and prevent public health risks.
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