ABSTRACT
Prior to the emergence of the Omicron variant, many cities in China had been able to maintain a "Zero-COVID" policy. They were able to achieve this without blanket city-wide lockdown and through widespread testing and an extensive set of nonpharmaceutical interventions (NPIs), such as mask wearing, contact tracing, and social distancing. We wanted to examine the effectiveness of such a policy in containing SARS-CoV-2 in the early stage of the pandemic. Therefore, we developed a fully stochastic, spatially structured, agent-based model of SARS-CoV-2 ancestral strain and reconstructed the Beijing Xinfadi outbreak through computational simulations. We found that screening for symptoms and among high-risk populations served as methods to discover cryptic community transmission in the early stage of the outbreak. Effective contact tracing could greatly reduce transmission. Targeted community lockdown and temporal mobility restriction could slow down the spatial spread of the virus, with much less of the population being affected. Population-wide mass testing could further improve the speed at which the outbreak is contained. Our analysis suggests that the containment of SARS-CoV-2 ancestral strains was certainly possible. Outbreak suppression and containment at the beginning of the pandemic, before the virus had the opportunity to undergo extensive adaptive evolution with increasing fitness in the human population, could be much more cost-effective in averting the overall pandemic disease burden and socioeconomic cost.
ABSTRACT
Background: Since December 2019, COVID-19 has rapidly swept the world. It is particularly important to understand the dynamic changes of the whole disease course of non-severe patients from the onset to the follow-up after discharge.Methods: On February 1, 2020, 18 cases of non-severe COVID-19 appeared in a hospital in Beijing. All patients were SARS-CoV-2 RNA positive by RT-PCR for pharyngeal swabs. We recorded the clinical information and viral dynamics of these patients from the onset of the disease to 2 months after discharge. According to the severity of lung consolidation, 18 patients were divided into two groups (mild pulmonary consolidation group [imaging score ≤10]; severe pulmonary consolidation group [imaging score >10]).Results: Eighteen patients (median age 43) were included, including 14 females. Fever (11/18) and cough (8/18) were the most common symptoms. The duration of SARS-CoV-2 RNA positive in mild pulmonary consolidation group was significantly longer than severe pulmonary consolidation group (the median time was 30 days and 13 days, respectively, P= 0.0031). Two months after discharge, almost all patients were followed up for IgM antibody disappearance and IgG antibody production.Conclusion: In non-severe COVID-19 patients, the positive duration of the SARS-CoV-2 RNA in patients with mild pulmonary consolidation was longer than the severe pulmonary consolidation. However, it is necessary for a large sample to verify our conclusions.