Natural history and cycle threshold values analysis of the first factory outbreak of the delta variant of COVID-19 in Xiamen, China (preprint)

Objective: This study elaborated the natural history parameters of Delta variant, explored the differences in detection cycle thresholds (Ct) among cases. Method: Natural history parameters were calculated based on the different onset times and exposure times of the cases. Intergenerational relationships between generations of cases were calculated. Differences in Ct values of cases by gender, age, and mode of detection were analyzed statistically to assess the detoxification capacity of cases. Result: The median incubation period was 4 days; the detection time for cases decreased from 25 to 7 hours as the outbreak continued. The mean intergenerational, intergenerational infectiousness and intergenerational symptomatology were 3.6, 1.67 and 1.7 days. Among the Ct values, we found little differences in testing across companies, but there were some differences in the gender of detected genes. The Ct values continuous to decreased with age, but increased when the age was greater than 60. Conclusion: This epidemic was caused by the aggregation of factories. The effective reproduction number and real-time reproduction number were calculated using symptom intergenerational relationship (SI). And the analysis of Ct values can improve the positive detection rate and improve prevention and control measures.

Feasibility of COVID-19 control from a pandemic to endemic (preprint)

Evaluations of the pandemic to endemic phase are a great concern, especially in Zero-COVID-19 countries. Herein, we developed a mathematical model to simulate future scenarios for the variants of concern (VOCs) in the condition of several immune barriers and controlling measures. The results demonstrated that the Omicron variant would lead to 592.0 (mean ± standard deviation (SD): 433.9–750.0) million symptomatic, 24.3 (mean ± SD: 17.4–312.8) million hospital admission, 9.6 (mean ± SD:7.0–12.3) million ICU admission, and 5.4 (mean ± SD:3.7–7.5) million death cases after simulation with 1,000 days. At the endemic phase, there were nearly 500 death cases per day attributed to reinfection (66% [range: 62–70%]), infection from birth (18% [range: 16–21%]), and infection from migration (16% [range: 14–17%]). Actively treating more than 80% of cases could effectively reduce disease severity and death rates. It is feasible to transmit pandemic to endemic with Omicron variant and other milder VOCs. We recommend that the successful transition strategy is to improve medical resource allocation and enhance the prevention and control capabilities of health agencies.