Since January 2020, Elsevier has established a COVID-19 resource center on Elsevier Connect, providing free information in English and Mandarin about the novel coronavirus. The company has granted permission to make all COVID-19-related research available in PubMed Central and other public repositories, with unrestricted reuse and analysis rights, as long as the resource center remains active. The article by Hiroshi Nishiura, Natalie M. Linton, and Andrei R. Akhmetzhanov estimates the serial interval of COVID-19 infections from 28 infector-infectee pairs. The median serial interval was estimated at 4.0 days (95% credible interval: 3.1-4.9), indicating that a significant proportion of secondary transmissions occur before the onset of symptoms. This is shorter than the median incubation period of approximately 5 days, suggesting rapid transmission cycles and pre-symptomatic transmission. The study also notes that the serial interval is shorter than that of SARS, which may introduce bias in using SARS data for calculations. The authors conclude that containment measures, such as case isolation, may be challenging due to the high rate of transmission.Since January 2020, Elsevier has established a COVID-19 resource center on Elsevier Connect, providing free information in English and Mandarin about the novel coronavirus. The company has granted permission to make all COVID-19-related research available in PubMed Central and other public repositories, with unrestricted reuse and analysis rights, as long as the resource center remains active. The article by Hiroshi Nishiura, Natalie M. Linton, and Andrei R. Akhmetzhanov estimates the serial interval of COVID-19 infections from 28 infector-infectee pairs. The median serial interval was estimated at 4.0 days (95% credible interval: 3.1-4.9), indicating that a significant proportion of secondary transmissions occur before the onset of symptoms. This is shorter than the median incubation period of approximately 5 days, suggesting rapid transmission cycles and pre-symptomatic transmission. The study also notes that the serial interval is shorter than that of SARS, which may introduce bias in using SARS data for calculations. The authors conclude that containment measures, such as case isolation, may be challenging due to the high rate of transmission.