Syrian hamster is a valuable animal model for evaluating the transmissibility of emerging influenza viruses.

Multiple influenza virus subtypes actively circulate in nature, and assessing their transmissibility provides crucial information for predicting their pandemic potential and for pandemic preparedness. Here, we evaluated the receptor-binding preferences, replication, and transmission of five different influenza viruses (i.e. CA/07-H1N1, GX/18-H1N1, CK/S2283-H3N8, CK/SD007-H9N2, and DK/35-H5N1) in Syrian hamsters. Receptor-binding analysis using biolayer interferometry revealed that four of these viruses preferentially bound α2,6-linked sialic acid receptors, whereas the H5N1 virus bound to α2,3-linked and α2,6-linked sialic acid receptors similarly. All five viruses replicated well in the respiratory tissues of Syrian hamsters, but did not cause obvious symptoms or death, indicating that Syrian hamsters can tolerate influenza virus infection and are not suitable for influenza virus pathogenicity studies. The four viruses that bound to α2,6-linked sialic acid receptors with higher affinity than to α2,3-linked sialic acid receptors were transmissible between Syrian hamsters via direct contact or respiratory droplets; however, the H5N1 virus was not transmissible through respiratory droplets, consistent with previously reported transmission characteristics observed for these viruses in guinea pigs and ferrets. Given that Syrian hamsters and humans have similar receptor expression patterns in their nasal mucosa, our findings suggests that Syrian hamsters can be used as a suitable animal model for evaluating the transmissibility of influenza viruses that preferentially bind to α2,6-linked sialic acid receptors.