Slight increase in fomite route transmission risk of SARS-CoV-2 Omicron variant compared with the ancestral strain in households

The Omicron SARS-CoV-2 variant has become the dominant lineage worldwide, and experimental study had shown that SARS-CoV-2 Omicron variant was more stable on various environmental surfaces than ancestral strain. However, how the changes of stability on surfaces would influence the role of fomite route in SARS-CoV-2 transmission is still unknown. In this study, we modeled the Omicron and ancestral strain SARS-CoV-2 transmission within a household over 1-day period from multiple pathways, i.e., airborne, droplet and contact route. We assumed there were 2 adults and 1 child in the household, and one of the adults was infected with SARS-CoV-2. We assume a scenario of pre-/asymptomatic infection, i.e., SARS-CoV-2 was emitted by breathing and talking, and symptomatic infection, i.e., SARS-CoV-2 was emitted by breathing, talking, and coughing. In pre-/asymptomatic infection, all three routes contributed a role, contact route contribute most (37%-45%), followed by airborne route (34%-38%) and droplet route (21%-28%). In symptomatic infection, droplet route was the dominant pathway (48%-71%), followed by contact route (25%-42%), airborne route played a negligible role (<10%). In the contact route, indirect contact (fomite) route dominated (contributed more than 97%). Compared with ancestral strain, though the contribution of contact route increased in Omicron variant transmission, the increase was slight, from 25%-41% to 30%-45%.