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

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.