Higher SARS-CoV-2 shedding in exhaled aerosol probably contributed to the enhanced transmissibility of Omicron BA.5 subvariant.

The global pandemic of the BA.5 subvariant had moved from prediction to reality. In this study, we compared SARS-CoV-2 aerosol emissions from patients with BA.2 or BA.5 subvariant infection. First, patients with BA.2 subvariant infection had higher upper respiratory viral loads than patients with BA.5 subvariant infection. However, the average breath emission rate (BER) of patients with BA.5 subvariant infection, which represented the concentration of exhaled SARS-CoV-2 aerosols, was nearly 40 times higher than that of patients with BA.2 subvariant. Second, aerosols exhaled by patients with BA.5 subvariant infection exhibited SARS-CoV-2 RNA detection positive rate than patients with BA.1 or BA.2 subvariant infection. Meanwhile, for BA.5 subvariant infection, patients that exhaled infectious SARS-CoV-2 aerosols accounted for 14.8% of all patients. Third, since the onset of COVID-19, the SARS-CoV-2 RNA detection signals of throat swabs showed a gradual decline trend, although the decline process was accompanied by fluctuations. Overall, the monitoring of infectious SARS-CoV-2 aerosols may provide the data support for the transmissibility evaluation of the Omicron BA.5 subvariant. This article is protected by copyright. All rights reserved.

Emerging Omicron subvariants evade neutralizing immunity elicited by vaccine or BA.1/BA.2 infection.

The newly emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron BA.2.75 and BA.2.76 subvariants contained 35 and 29 additional mutations in its spike (S) protein compared with the reference SARS-CoV-2 genome, respectively. Here, we measured the evasion degree of the BA.1, BA.2, BA.4, BA.5, BA.2.75, and BA.2.76 subvariants from neutralizing immunity in people previously infected with the Omicron BA.1 and BA.2, determined the effect of vaccination on immune evasion, and compared the titers of neutralizing antibodies in serums between acute infection and convalescence. Results showed that the neutralization effect of serums from patients with different vaccination statuses and BA.1/BA.2 breakthrough infection decreased with the Omicron evolution from BA.1 to BA.2, BA.4, BA.5, BA.2.75, and BA.2.76. This study also indicated that the existing vaccines could no longer provide effective protection, especially for the emerging BA.2.75 and BA.2.76 subvariants. Therefore, vaccines against emerging epidemic strains should be designed specifically. In the future, we can not only focus on the current strains, but also predict and design new vaccines against potential mutant strains. At the same time, we can combine the virus strains' infection characteristics to develop protective measures for virus colonization areas, such as nasal protection spray. Besides, further studies on the Y248N mutation of BA.2.76 subvariant were also necessary to explore its contribution to the enhanced immune evasion ability.

Visualization of the infection risk assessment of SARS-CoV-2 through aerosol and surface transmission in a negative-pressure ward.

Since December 2019, coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a great challenge to the world's public health system. Nosocomial infections have occurred frequently in medical institutions worldwide during this pandemic. Thus, there is an urgent need to construct an effective surveillance and early warning system for pathogen exposure and infection to prevent nosocomial infections in negative-pressure wards. In this study, visualization and construction of an infection risk assessment of SARS-CoV-2 through aerosol and surface transmission in a negative-pressure ward were performed to describe the distribution regularity and infection risk of SARS-CoV-2, the critical factors of infection, the air changes per hour (ACHs) and the viral variation that affect infection risk. The SARS-CoV-2 distribution data from this model were verified by field test data from the Wuhan Huoshenshan Hospital ICU ward. ACHs have a great impact on the infection risk from airborne exposure, while they have little effect on the infection risk from surface exposure. The variant strains demonstrated significantly increased viral loads and risks of infection. The level of protection for nurses and surgeons should be increased when treating patients infected with variant strains, and new disinfection methods, electrostatic adsorption and other air purification methods should be used in all human environments. The results of this study may provide a theoretical reference and technical support for reducing the occurrence of nosocomial infections.