SARS-CoV-2 Omicron variant shedding during respiratory activities

Abstract

Objectives: As the world transitions to COVID-19 endemicity, studies focusing on aerosol shedding of highly transmissible SARS-CoV-2 variants of concern (VOCs) are vital for the calibration of infection control measures against VOCs that are likely to circulate seasonally. This follow-up Gesundheit-II aerosol sampling study aims to compare the aerosol shedding patterns of Omicron VOC samples with pre-Omicron variants analyzed in our previous study.

Design: Coarse and fine aerosol samples from 47 patients infected with SARS-CoV-2 were collected during various respiratory activities (passive breathing, talking, and singing) and analyzed using reverse transcription-quantitative polymerase chain reaction and virus culture.

Results: Compared with patients infected with pre-Omicron variants, comparable SARS-CoV-2 RNA copy numbers were detectable in aerosol samples of patients infected with Omicron despite being fully vaccinated. Patients infected with Omicron also showed a slight increase in viral aerosol shedding during breathing activities and were more likely to have persistent aerosol shedding beyond 7 days after disease onset.

Conclusion: This follow-up study reaffirms the aerosol shedding properties of Omicron and should guide continued layering of public health interventions even in highly vaccinated populations.

Keywords: Aerosol transmission; Airborne transmission; COVID-19; Omicron variant of concern; SARS-CoV-2.

Graphical abstract

Figure 1

Detection of SARS-CoV-2 RNA copy numbers in all SARS-CoV-2 infected patients’ aerosol samples from different respiratory activities. (a) SARS-CoV-2 RNA copy numbers in fine aerosol fractions from breathing, talking, and singing. (b) SARS-CoV-2 RNA copy numbers in coarse aerosol fractions from breathing, talking, and singing. All plots are shown as median values of SARS-CoV-2 RNA copy numbers from detected samples only. Statistical significance was calculated using Kruskal-Wallis test with Dunn correction for multiple comparison. A P-value of P <0.05 is considered statistically significant.

Figure 2

Comparison of SARS-CoV-2 RNA copy numbers from patients infected with pre-Omicron vs Omicron variant of concerns. Comparison of viral RNA copy numbers in fine and coarse fractions of aerosol samples from (a) breathing, (b) talking, and (c) singing activities. All non-Omicron variants were consolidated as the pre-Omicron group for comparison with the Omicron group. The color of each datapoint indicates the patients’ SARS-CoV-2 vaccination status. All plots are shown as median values of SARS-CoV-2 RNA copy numbers. Statistical significance was calculated using the Mann-Whitney U test. A P-value of P <0.05 is considered statistically significant.

Figure 3

SARS-CoV-2 RNA copy numbers over day of illnesses between pre-Omicron and Omicron variant of concerns. Total RNA copy numbers from both fine and coarse (f + c) fractions are consolidated and plotted against day of illness for (a) breathing, (b) talking and (c) singing activities. The black data points represent the pre-Omicron samples, whereas the green data points represent the Omicron samples.

Figure 4

Comparison of SARS-CoV-2 RNA copy numbers of pre-Omicron versus Omicron variants in fine and coarse fractions at late phase of illness (≥7 days). Comparison of viral RNA copy numbers in both fine and coarse fractions of aerosol samples from (a) breathing, (b) talking, and (c) singing activities. The day of illness denotes the number of days that elapsed since positive diagnosis of SARS-CoV-2 infection. All non-Omicron variants were consolidated as the pre-Omicron group for comparison with the Omicron group. All plots are shown as median values of SARS-CoV-2 RNA copy numbers. Statistical significance was calculated using Kruskal-Wallis test with Dunn correction for multiple comparison. A P-value of P <0.05 is considered statistically significant.