Epidemiological and transmission characteristics comparison analysis between Delta and Omicron variants of the SARS-CoV-2 (BA.2.1, BA.2.2, BA.2.76, BA.5.2) (preprint)

Since the outbreak of coronavirus disease 2019 (COVID-19), the virus has undergone three mutations, with Delta and Omicron being the most affected.This study aimed to understand the epidemiology and transmission differences between the Delta and Omicron variants, and to analyze the infection characteristics of different variants, providing a scientific theoretical basis for prevention and control strategies.We conducted a comparative analysis by selecting six local outbreaks of the Delta variant that occurred in Hunan Province in July 2021 and six local outbreaks of different sub-lineages of the Omicron variant that occurred in 2022. The results showed that asymptomatic cases were more prevalent in Omicron variant infections, with BA.5.2 having the highest proportion. The Delta and Omicron variants have identical median incubation periods of 2–3 days. In terms of secondary situations, the secondary attack rate of the Delta variant is 0.85%, while that of the Omicron variant is 1.69%. For specific Omicron subvariants, Omicron BA.2.1 has a secondary attack rate of 0.89%, Omicron BA.2.2 is 0.71%, Omicron BA.2.76 is 2.51%, and Omicron BA.5.2 has a secondary attack rate of 4.63%. The predominant mode of exposure for cases with recurrent infections of the Delta variant is cohabitation, while for Omicron variant outbreaks, cohabitation remains predominant, followed by spatial proximity and dining together.The Delta variant and the Omicron variant are both make it prone to causing multiple generations of cases in a short period, leading to a wider impact. The secondary attack rates of Omicron and Delta variants in this study were much lower than in other countries, indicating that strengthening personnel control and social regulations are beneficial for the prevention and control of newly emerging severe infectious diseases. Meanwhile, the exposure types of Omicron variant secondary cases were more diverse, and the symptoms of infected individuals were milder, indicating its greater stealthiness. Therefore, it is crucial to focus on virus mutations, strengthen surveillance, and increase prevention and control efforts if enhanced transmissibility of the variant is detected.

Antiviral effects of Atractyloside A on the influenza B virus (Victoria strain) infection

Influenza viruses pose a serious threat to human health, infecting hundreds of millions of people worldwide each year, resulting in a significant increase in global morbidity and mortality. Influenza activity has declined at the onset of the COVID-19 pandemic, but the genetic diversity of B/Victoria lineage viruses has increased significantly during this period. Therefore, the prevention and treatment of the influenza B Victoria strain virus should continue to attract research attention. In this study, we found that Atractyloside A (AA), one of the effective components in Atractylodes lancea (Thunb.) DC shows potential antiviral properties. This study shows that AA not only possesses anti-influenza B virus infection effects in vivo and in vitro but also can regulate macrophage polarization to the M2 type, which can effectively attenuate the damage caused by influenza B virus infection. Therefore, Atractyloside A may be an effective natural drug against B/Victoria influenza infection.