Incubation periods of acute respiratory viral infections: a systematic review

Abstract

Knowledge of the incubation period is essential in the investigation and control of infectious disease, but statements of incubation period are often poorly referenced, inconsistent, or based on limited data. In a systematic review of the literature on nine respiratory viral infections of public-health importance, we identified 436 articles with statements of incubation period and 38 with data for pooled analysis. We fitted a log-normal distribution to pooled data and found the median incubation period to be 5.6 days (95% CI 4.8-6.3) for adenovirus, 3.2 days (95% CI 2.8-3.7) for human coronavirus, 4.0 days (95% CI 3.6-4.4) for severe acute respiratory syndrome coronavirus, 1.4 days (95% CI 1.3-1.5) for influenza A, 0.6 days (95% CI 0.5-0.6) for influenza B, 12.5 days (95% CI 11.8-13.3) for measles, 2.6 days (95% CI 2.1-3.1) for parainfluenza, 4.4 days (95% CI 3.9-4.9) for respiratory syncytial virus, and 1.9 days (95% CI 1.4-2.4) for rhinovirus. When using the incubation period, it is important to consider its full distribution: the right tail for quarantine policy, the central regions for likely times and sources of infection, and the full distribution for models used in pandemic planning. Our estimates combine published data to give the detail necessary for these and other applications.

Figure 1

Systematic review process

Figure 2

Parametric and non-parametric estimates of the incubation period Cumulative percentage of cases developing symptoms by a given day under the estimates for the log-normal distribution (continuous line) are shown, compared with the non-parametric estimates calculated by the method of Turnbull (rectangles). Rectangular regions represent estimates with equivalent support (ie, not statistically distinguishable). RSV=respiratory syncytial virus. SARS=severe acute respiratory syndrome.