An important caveat is that other viral and cellular factors could have contributed to the smaller foci in addition to an impairment of the cell-cell fusogenic potential of Omicron spike, for example ACE2 dependent cell-cell infection by budding virions across virological synapses, and ability of IFITMs to restrict fusion30 in the context of Omicron virus infection. The gene discussed is ACE2; the disease is viral infectious disease.