AART (Association for the Advancement of Research on Transplantation), Cagliari, Italy.
Complex Structure of Medical Genetics, R. Binaghi Hospital, ASSL Cagliari, ATS Sardegna, Italy.
Int J Infect Dis. 2021 Mar;104:262-268. doi: 10.1016/j.ijid.2021.01.010. Epub 2021 Jan 9.
Epidemiological investigations and mathematical models have revealed that the rapid diffusion of Covid-19 can mostly be attributed to undetected infective individuals who continue to circulate and spread the disease: finding their number would be of great importance in the control of the epidemic.
The dynamics of an infection can be described by the SIR model, which divides the population into susceptible (S), infective I, and removed R subjects. In particular, we exploited the Kermack-McKendrick epidemic model, which can be applied when the population is much larger than the fraction of infected subjects.
We proved that the fraction of undetected infectives, compared to the total number of infected subjects, is given by 1-1R, where R is the basic reproduction number. The mean value R=2.102.09-2.11 for the Covid-19 epidemic in three Italian regions yielded a percentage of undetected infectives of 52.4% (52.2%-52.6%) compared to the total number of infectives.
Our results, straightforwardly obtained from the SIR model, highlight the role of undetected carriers in the transmission and spread of the SARS-CoV-2 infection. Such evidence strongly recommends careful monitoring of the infective population and ongoing adjustment of preventive measures for disease control until a vaccine becomes available for most of the population.
流行病学调查和数学模型表明，Covid-19 的快速传播主要归因于未被发现的具有传染性的个体，他们继续传播疾病：确定他们的数量对于控制疫情非常重要。
感染的动力学可以用 SIR 模型来描述，该模型将人群分为易感者（S）、感染者（I）和被移除者（R）。具体来说，我们利用了 Kermack-McKendrick 传染病模型，当人群远大于感染者的比例时，可以应用该模型。
我们证明，未被发现的感染者比例相对于感染者总数，为 1-1R，其中 R 是基本繁殖数。意大利三个地区的 Covid-19 疫情的平均值 R=2.102.09-2.11，得出未被发现的感染者比例为 52.4%（52.2%-52.6%），相对于感染者总数。
我们从 SIR 模型直接得到的结果，突出了未被发现的携带者在 SARS-CoV-2 感染传播和扩散中的作用。这些证据强烈建议对感染人群进行仔细监测，并在疫苗为大多数人群提供之前，持续调整疾病控制的预防措施。
