Dynamic Zero-Covid strategy curtails mutagenesis and emergence of new variants of the SARS-CoV-2 (preprint)

Within the local outbreak period of SARS-CoV-2 Delta variant in Nanjing and Yangzhou, China, we analyzed the mutation process of the Delta variants in 520 cases, as well as the production, spread and elimination of new mutant strains under the non-pharmaceutical interventions (NPI) strategy. The investigation on distribution of COVID-19 cases and phylogenetic analysis of SARS-CoV-2 genome sequences attributed to tracking the transmission chains, transmission chains were terminated by the isolation of the COVID-19 patients and quarantine of close-contracts, suggesting the importance of NPI in prompting some mutations to disappear and stopping the transmission of new variants. Dynamic zero-Covid strategy has been implemented successfully to against the second-largest local epidemic caused by an imported COVID-19 case in China.

Early warning signs for severe patients with Coronavirus Disease 2019 and its epidemical significance (preprint)

Background Since December 2019 coronavirus disease 2019 (COVID-19) emerged in Wuhan city and rapidly spread throughout China. However, early warning signs for severe patients with COVID-19 were not fully known.Methods Information on admission was collected through a standard questionnaire. We described the epidemiological characteristics of the patients with COVID-19, analyzed the risk factors associated with severe illness, and estimated the key epidemiologic time-delay distributions.Results A total of 631 patients with laboratory-confirmed COVID-19 were identified. The proportion of severe cases was 8.4%. The epidemic of COVID-19 experienced four stages: sporadic phase, exponential growth phase, peak plateau phase, and declining phase. The proportion of severe cases was significantly different in four stages and 13 municipal prefectures (P < 0.001). Factors including elderly more than 65years(yrs) old, underlying medical conditions, fever patient whose highest temperature beyond 39.0℃, dyspnea, and lymphocytopenia(< 1.0 × 109/L) could possibly become the early warning signs for severe patients of COVID-19. In contrast, earlier visit to the clinic could reduce the severe risk. Besides, the viral load may be a potentially useful marker associated with disease severity of COVID-19 infection.Conclusions The epidemic experienced four stages with obviously areas difference. People aged beyond 65 yrs or underlying medical conditions once appear symptoms like fever beyond 39.0℃ and/or dyspnea should immediately visit health care.

Effectiveness and cost-effectiveness of public health measures to control COVID-19: a modelling study (preprint)

BackgroundThe Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) was first reported in China, which caused a respiratory disease known as Coronavirus Disease 2019 (COVID-19). Since its discovery, the virus has spread to over 160 countries and claimed more than 9800 deaths. This study aimed to assess the effectiveness and cost-effectiveness of various response public health measures. MethodsThe stochastic agent-based model was used to simulate the process of COVID-19 outbreak in scenario I (imported one case) and II (imported four cases) with a series of public health measures, involving the personal protection, isolation-and-quarantine, gathering restriction, and community containment. The virtual community was constructed following the susceptible-latent-infectious-recovered framework. The epidemiological and economic parameters derived from the previous literature and field investigation. The main outcomes included avoided infectors, cost-effectiveness ratios (CERs), and incremental cost-effectiveness ratios (ICERs). The sensitivity analyses were undertaken to assess uncertainty. ResultsIn scenario I and II, the isolation-and-quarantine averted 1696 and 1990 humans infected respectively at the cost of US$12 428 and US$58 555, both with negative value of ICERs. The joint strategy of personal protection and isolation-and-quarantine could avert one more case than single isolation-and-quarantine with additional cost of US$166 871 and US$180 140 respectively. The effectiveness of isolation-and-quarantine decreased as lowering quarantine probability and increasing delay-time. Especially in scenario II, when the quarantine probability was less than 25%, the number of infections raised sharply; when the quarantine delay-time reached six days, more than a quarter of individuals would be infected in the community. The strategy including community containment could protect more lives and was cost-effective, when the number of imported cases was no less than 65, or the delay-time of quarantine was more than five days, or the quarantine probability was below 25%, based on current assumptions. ConclusionsThe isolation-and-quarantine was the most cost-effective intervention. However, personal protection and isolation-and-quarantine was the optimal strategy averting more infectors than single isolation-and-quarantine. Certain restrictions should be considered, such as more initial imported cases, longer quarantine delay-time and lower quarantine probability.