Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2020 Apr:93:284-286.
doi: 10.1016/j.ijid.2020.02.060. Epub 2020 Mar 4.

Serial interval of novel coronavirus (COVID-19) infections

Hiroshi Nishiura  1 , Natalie M Linton  2 , Andrei R Akhmetzhanov  2
Affiliations

Serial interval of novel coronavirus (COVID-19) infections

Hiroshi Nishiura et al. Int J Infect Dis. 2020 Apr.

Abstract

Objective: To estimate the serial interval of novel coronavirus (COVID-19) from information on 28 infector-infectee pairs.

Methods: We collected dates of illness onset for primary cases (infectors) and secondary cases (infectees) from published research articles and case investigation reports. We subjectively ranked the credibility of the data and performed analyses on both the full dataset (n = 28) and a subset of pairs with highest certainty in reporting (n = 18). In addition, we adjust for right truncation of the data as the epidemic is still in its growth phase.

Results: Accounting for right truncation and analyzing all pairs, we estimated the median serial interval at 4.0 days (95% credible interval [CrI]: 3.1, 4.9). Limiting our data to only the most certain pairs, the median serial interval was estimated at 4.6 days (95% CrI: 3.5, 5.9).

Conclusions: The serial interval of COVID-19 is close to or shorter than its median incubation period. This suggests that a substantial proportion of secondary transmission may occur prior to illness onset. The COVID-19 serial interval is also shorter than the serial interval of severe acute respiratory syndrome (SARS), indicating that calculations made using the SARS serial interval may introduce bias.

Keywords: Coronavirus; Epidemiology; Generation time; Illness onset; Outbreak; Statistical model; Viruses.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Serial interval of novel coronavirus (COVID-19) infections. The solid line shows the estimated serial interval distribution of COVID-19 infections using the best-fit lognormal distribution with right truncation. A distribution based on a published estimate of the serial interval for severe acute respiratory syndrome (Lipsitch et al., 2003) is overlaid as a dashed line for comparison.
Figure 2
Figure 2
The relationship between the incubation period and serial interval. If the transmission takes place during the symptomatic period of the primary case, the serial interval is longer than the incubation period. However, this relationship can be reversed when pre-symptomatic transmission takes place. Furthermore, it is possible that the secondary case may even experience illness onset prior to onset in their infector.
See this image and copyright information in PMC

References

    1. Fine P.E. The interval between successive cases of an infectious disease. Am J Epidemiol. 2003;158:1039–1047. - PubMed
    1. Fraser C., Riley S., Anderson R.M., Ferguson N.M. Factors that make an infectious disease outbreak controllable. Proc Natl Acad Sci U S A. 2004;101(16):6146–6151. - PMC - PubMed
    1. Jung S., Akhmetzhanov A.R., Hayashi K., Linton N.M., Yang Y., Yuan B. Real-time estimation of the risk of death from novel coronavirus (COVID-19) infection: inference using exported cases. J Clin Med. 2020;9(2) doi: 10.3390/jcm9020523. - DOI - PMC - PubMed
    1. Li Q., Guan X., Wu P., Wang X., Zhou L., Tong Y. Early transmission dynamics in Wuhan, China, of novel coronavirus-infected pneumonia. N Engl J Med. 2020 doi: 10.1056/NEJMoa2001316. in press. - DOI - PMC - PubMed
    1. Linton N.M., Kobayashi T., Yang Y., Hayashi K., Andrei A.R., Jung S. Incubation period and other epidemiological characteristics of 2019 novel coronavirus infections with right truncation: a statistical analysis of publicly available case data. J Clin Med. 2020;9(2) doi: 10.3390/jcm9020538. - DOI - PMC - PubMed