Abstract
Transmissibility has increased during the evolution of SARS-CoV-2, possibly by improved airborne transmission. An increased transmission was noted also in many hospitals. We analyzed SARS-CoV-2 in room air of hospitalized Omicron infected patients and compared results with previous findings with pre-Delta variants to study if SARS-CoV-2 was more prevalent in patient rooms after the introduction of Omicron. Only 4 of 75 (5%) air samples, from 3 of 43 included patients, were positive during the early Omicron wave, compared to 14/120 (12%), from 10 of 60 included patients during the initial wave. No certain statistical difference between virus variants could be established, but the tendency was a lower occurrence at Omicron infected patients, also when adjusting for relevant confounders. These finding do not support the initial hypothesis that increased SARS-CoV-2 aerosol emission from diagnosed patients with Omicron could explain any increased risk of hospital transmission.