McAloon Conor G, Wall Patrick, Griffin John, Casey Miriam, Barber Ann, Codd Mary, Gormley Eamonn, Butler Francis, McV Messam Locksley L, Walsh Cathal, Teljeur Conor, Smyth Breda, Nolan Philip, Green Martin J, O'Grady Luke, Culhane Kieran, Buckley Claire, Carroll Ciara, Doyle Sarah, Martin Jennifer, More Simon J
School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
School of Public Health, Physiotherapy and Sports Science, University College Dublin, Belfield, Dublin 4, Ireland.
BMC Public Health. 2021 Apr 27;21(1):805. doi: 10.1186/s12889-021-10868-9.
The serial interval is the period of time between the onset of symptoms in an infector and an infectee and is an important parameter which can impact on the estimation of the reproduction number. Whilst several parameters influencing infection transmission are expected to be consistent across populations, the serial interval can vary across and within populations over time. Therefore, local estimates are preferable for use in epidemiological models developed at a regional level. We used data collected as part of the national contact tracing process in Ireland to estimate the serial interval of SARS-CoV-2 infection in the Irish population, and to estimate the proportion of transmission events that occurred prior to the onset of symptoms.
After data cleaning, the final dataset consisted of 471 infected close contacts from 471 primary cases. The median serial interval was 4 days, mean serial interval was 4.0 (95% confidence intervals 3.7, 4.3) days, whilst the 25th and 75th percentiles were 2 and 6 days respectively. We found that intervals were lower when the primary or secondary case were in the older age cohort (greater than 64 years). Simulating from an incubation period distribution from international literature, we estimated that 67% of transmission events had greater than 50% probability of occurring prior to the onset of symptoms in the infector.
Whilst our analysis was based on a large sample size, data were collected for the primary purpose of interrupting transmission chains. Similar to other studies estimating the serial interval, our analysis is restricted to transmission pairs where the infector is known with some degree of certainty. Such pairs may represent more intense contacts with infected individuals than might occur in the overall population. It is therefore possible that our analysis is biased towards shorter serial intervals than the overall population.
潜伏期是指感染者和被感染者症状出现之间的时间间隔，是一个重要参数，会影响繁殖数的估计。虽然预计影响感染传播的几个参数在不同人群中是一致的，但潜伏期会随时间在不同人群之间以及人群内部发生变化。因此，在区域层面开发的流行病学模型中，使用本地估计值更为可取。我们利用爱尔兰全国接触者追踪过程中收集的数据，来估计爱尔兰人群中新冠病毒感染的潜伏期，并估计在症状出现之前发生的传播事件的比例。
数据清理后，最终数据集包括来自471例原发病例的471名受感染密切接触者。中位数潜伏期为4天，平均潜伏期为4.0（95%置信区间3.7，4.3）天，而第25和第75百分位数分别为2天和6天。我们发现，当原发病例或继发病例属于老年队列（大于64岁）时，潜伏期较短。根据国际文献中的潜伏期分布进行模拟，我们估计67%的传播事件在感染者症状出现之前发生的概率大于50%。
虽然我们的分析基于大样本量，但数据收集的主要目的是中断传播链。与其他估计潜伏期的研究类似，我们的分析仅限于感染源在一定程度上确定已知的传播对。这类传播对可能代表与受感染个体的接触比总体人群中可能发生的接触更为密切。因此，我们的分析有可能偏向于比总体人群更短的潜伏期。
