Severe Acute Respiratory Syndrome Coronavirus 2 Omicron Variant Kinetics in Natural Infection: A Case Study

Abstract

Background Omicron has become the mainstream epidemic variant of severe acute respiratory syndrome coronavirus 2 worldwide. One reason for the high infectivity of this variant is its ability to multiply rapidly in the human body. It has been speculated that, in general, the short period required for virus multiplication affects the incubation period and timing of viral shedding that begins during the incubation period. However, it is unclear whether these effects can be related to the Omicron variant. Similar to a recent human challenge study, in this study, patients with known timing of Omicron infection were followed up in a hospital before the onset of the disease. 
 Methods In two patients, the viral shedding was investigated and analysed along with symptoms before and after the disease onset.
 Results The incubation period for Omicron was 30-36 h; this was shorter than the average incubation period of the alpha variant in the human challenge study and that reported in a systematic review and meta-analysis (3.5 days). Viral shedding at the nasal site began 19-22 h after infection, approximately 10 h before symptom onset.
 Conclusion The results of this study demonstrated that in some instances with Omicron (BA.5), the time to viral shedding and the time to disease onset were considerably shorter after infection than those previously reported for Omicron and Alpha variants. We showed the importance of early detection of the viral antigen after viral exposure and early isolation initiation to prevent infection spread.