Background
Methods
Criteria for considering studies for this review
Types of studies
Types of participants
Types of outcome measures
Search methods for identification of studies
Electronic searches
Data collection and analysis
Selection of studies and data extraction
Assessment of risk of bias
Data synthesis
Results
Results of the search
Study characteristics
Authors | Country (province) | Period | Data and source collection | General characteristics of the population study | Exposure history | ||
---|---|---|---|---|---|---|---|
N | Age┼┼ (years) | Sex ratio (M/F) | |||||
Guan et al. [27] | China | 11/12/2019 to 29/01/2020 | 552 hospitals’ medical records | 1099 | Median =47 IQR [35-58] | 1.43 | Contact with wildlife Resident or travelers to Wuhan |
Ki and Task Force for 2019-nCoV [28] | Korea | 20/01/2020 to 10/02/2020 | CDC Additional data announced by the press | 28 | Mean= 42 Range (20–73) | 1.15 | Close contact with confirmed cases |
Chen et al. [43] | China (Chongqing) | 28/01/2020 to 11/02/2020 | 3 hospitals’ medical records | 12 | Mean=14.5 range (7M–17Y) | 1 | Resident or travelers to Wuhan Close contact with confirmed cases |
Gao et al. [7] | China (Wuxi) | January–March 2020 | Data of scientific investigation from “Public Health Emergency Reporting Management Information System” | 15 | Median= 51 Range (9–74) | 1.5 | Close contact with confirmed cases |
Huang et al. [8] | China (Anhui) | January–February 2020 | Information from patients and contacts. | 17 | Median=22 Range (16–23) | 0.75 | Close Contact with confirmed cases |
Pung et al. [38] | Singapore | February 2020 | The ministry of health (first three clusters) | 36 | - - | - | Close contact with a tourist group from China Public place (company conference/church) |
Song et al. [39] | China (Beijing) | 16/01/2020 to 29/01/2020 | 1 hospital’s medical records (4 families) | 24 | Range (9M–86 Y) | 0.37 | Close contact with confirmed cases |
Tian et al. [44] | China (Beijing) | 20/01/2020 to 10/02/2020 | 57 hospitals’ medical records | 262 | Median =47.5 Range (6M–94 Y ) | 0.94 | Wuhan travel Close contact with confirmed cases Family cluster cases |
Wang et al. [25] | China (Jiangsu ) | 22/01/2020 to 18/02/2020 | Websites of bureau of health and the people’s government. | 631 | - - | >1 | Resident or travelers to Hubei province Close contact with confirmed cases Others |
Xia et al. [40] | China (Chongqing) | 23/01/2020 to 18/02/2020 | Hospital electronic medical record system of patient with severe acute respiratory syndrome | 10 | Mean =56.5±11.16 | 1.5 | Close contact with confirmed cases |
Xu et al. [54] | China (Changzhou) | 23/01/2020 to 18/02/2020 | Laboratory-confirmed cases | 51 | Mean =35.0 Range (29–51) | 0.96 | Resident or travelers to Wuhan Close contact with confirmed or suspected cases |
Bernard et al. [41] | France | 24/01/2020 to 12/02/2020 | Unspecified | 3 | - | - | - |
Yu et al. [30] | China (Shanghai) | As of February 19th, 2020. | CDC | 333 | Median =50 | 1.06 | Cases with a travel history in Wuhan Close contact with confirmed cases |
Li et al. [20] | China (Wuhan) | December 2019 to 22 January 2020 | Laboratory-confirmed cases of infected pneumonia(NCIP) | 425 | Median= 59 Range(15 to 89) | 1.29 | Contact with wildlife Close contact with suspected cases |
Zhang et al. [23] | China outside Hubei | 19/01/2020 to 17/02/ 2020 | Laboratory-confirmed cases | 8579 | Median= 44 Range (33–56) | - | Contact with wildlife Close contact with confirmed or suspected cases Resident or travelers to Wuhan |
Linton et al. [29] | China | December 2019 to January 2020 | Official reports from governmental institutes | 158 | Most (30–59) | 0.58 | Resident or travelers to Wuhan |
Backer et al. [55] | China | 20 to 28 January 2020 | CDC | 88 | Range (2–72) | 1.84 | Travelers to Wuhan |
Lauer et al. [56] | China 24 countries outside China | 04/01/2020 to 24/02/2020 | Public health reports and news | 181 | Median= 44.5 IQR [34.0–55.5] | 1.56 | Resident or travelers to Wuhan Close contact with confirmed cases or travelers from Hubei |
Wang et al. [57] | China (Henan) | 21/01/2020 to 14/02/2020 | CDC | 1212 | Most (21–60) | 1.22 | Travelers to Wuhan Close contact with confirmed cases |
Bi et al. [24] | China (Shenzhen) | 14/01/2020 to 12/02/2020 | CDC | 3911 | Mean=45 | 0.91 | Travelers to Wuhan Close contact with confirmed cases |
Zheng et al. [45] | China (Hubei) | 16/01/2020 to 04/02/2020 | Taihe Hospital medical records | 73 | Mean=43 | 1.73 | Huanan China Seafood Market 12 cases had no exposure history Family cluster cases |
Zhao et al. [46] | China (Jiangsu ) | 16/01/2020 to 17/02/2020 | Jiangsu Hospital medical records | 136 | Median=49 IQR [33-63] | 1 | Resident or travelers to Wuhan Close contact with confirmed cases Family cluster cases 14 cases had no exposure history |
Zhang et al. [59] | China (Hubei) | 22/01/2020 to 28/02/2020 | Huanggang Hospital Shandong First Medical University | 194 | Median=48.3 | 1.25 | Contact with wildlife Resident or travelers to Wuhan |
Yang et al. [26] | China (Hubei) | 20/01/2020 to 29/02/2020 | CDC | 672 | Range (35–64) | 1.08 | Wuhan-imported Close contact of imported cases Locally infected |
Xiao et al. [31] | China (Hubei, Qinghai, Tibet) | As of February 21th, 2020. | CDC | 4741 | Median =50 | 1.06 | Resident or travelers to Wuhan Local community transmission |
Wong et al. [32] | Brunei | 09/03/2020 to 05/04/2020 | CDC | 135 | Median= 36 Range(0.5–72) | 1.54 | Travel history outside Brunei Local community transmission |
Wang et al. [47] | China (Wuhan) | 05/01/2020 to 12/02/2020 | Wuhan Union Hospital | 35 | Median= 37 Range(25–88) | 0.59 | 27 health care worker 10 relatives to health care worker |
Viego et al. [33] | Argentina (Bahia Blanca) | 20/03/2020 to 08/05/2020 | Local health authorities | 36 | - | - | Travel history outside city Local community transmission |
Tindale et al. [52] | Singapore | 23/01/2020 to 26/02/2020 | Publicly available data | 93 | - | - | |
China (Tianjin) | 21/01/2020 to 22/02/2020 | 135 | - | ||||
Tan et al. [48] | Singapore | 23/01/2020 to 02/04/2020 | Hospital records | 164 | Mean = 44.2 ±15.8 | 0.88 | Travel history Local community transmission |
Ryu et al. [34] | South Korea | 20/01/2020 to 21/04/2020 | Local public health authorities | 2023 | Median= 42 Range(1–102) | 0.24 | Clusters Imported from Daegu-Gyeongsangbuk or abroad Local transmission |
Qin et al. [35] | China (outside Hubei) Other countries | as of 15 February 2020 | Publicly available data in China The ministries of health in other countries | 1084 | Mean = 41.31 Median= 40 | 1.31 | - |
Nie et al. [60] | China (outside Hubei) | 19/01/2020 to 08/02/2020 | The website of the National Health Commission of the People’s Republic of China The health commission website of each province or city. | 7015 | Mean = 44.24 Range (2 m–97 y) | 1.11 | Resident or travelers to Wuhan Close contact with confirmed cases |
Lou et al. [50] | China | 19/01/2020 to 09/02/2020 | Hospital records | 80 | Median=55 IQR [45-64] | 1.58 | - |
Liu et al. [62] | China (Shenzhen) | 04/01/2020 to 05/02/2020 | 365 | Median=46 Range (1–86) | 0.99 | Contact with confirmed case-patients Wuhan Cities other than Wuhan in Hubei Province No definite exposure | |
Li et al. [49] | China (Shenzhen) | 21/01/2020 to 09/02/2020 | Hospital records | 74 | Mean = 44.26 | 0.89 | Travelers to Wuhan Family clusters Sporadic cases |
Lee et al. [51] | South Korea | 20/02/2020 to 03/03/2020 | Publicly available data | 47 | Median=30 Range (17–83) | - | - |
Chun et al. [9] | South Korea | 23/01/2020 to 31/03/2020 | Public reports of confirmed COVID-19 patients by the government and each municipal website in South Korea | 72 | Median=40 IQR [24-54] | 0.89 | Contact with confirmed cases |
Alsofayan et al. [53] | Saudi Arabia | 01/03/2020 to 31/03/2020 | Health Electronic Surveillance Network (HESN) Database | 1519 | Median=36 | 1.18 | History of recent travel outside KSA Local community transmission |
Bohmer et al. [42] | Germany (Bavaria) | 27/01/2020 to 16/02/2020 | Bavarian Health and Food Safety Authority and national level (Robert Koch Institute) public health authorities and four public health laboratories. | 16 | Median=35 IQR [27-42] Range (2–58) | 3.0 | Cluster |
You et al. [36] | China (outside Hubei province) | 01/01/2020 to 31/03/2020 | The National Health Commission (NHC) of China | 169 | - | - | Resident or travelers to Hubei |
Wieland [37] | Germany | 15/02/2020 to 31/03/2020 | Official German case data | 107 | - | - | - |
Risk of bias within studies
Results of individual studies
Based on studies calculating incubation period for SARS-CoV-2
Authors | (n/N)┼ | Incubation period (days) | ||
---|---|---|---|---|
Median [IQR] | Mean±SD | Range | ||
Guan et al. [27] | 291/1099 | 4 [2.0–7.0] | - | - |
Ki and Task Force for 2019-nCoV [28] | 10/28 | 3 | 3.9 | 0–15 |
Chen et al. [43] | 12/ 12 | - | 8 | 1–13 |
Gao et al. [7] | 6/15 | 10 | - | 3–12 |
Huang et al. [8] | 6/8 | 2.0 | - | 1–4 |
Pung et al. [38] | 19/36 | 4 [3.0–6.0] | - | - |
Song et al. [39] | 22/24 | - | - | 2–13 |
Tian et al. [44] | 262/262 | - | 6.7 ±5.2 | - |
Wang et al. [25] | 631/631 | - | Max 19 | |
Xia et al. [40] | 9/10 | - | 7 ± 2.59 | 2–14 |
Xu et al. [54] Imported Secondary Tertiary | 15/51 17/51 19/51 | 8 [4.0–10.0] 8 [4.0–11.0] 12 [9.0–14.0] | - | - |
Bernard et al. [41] | 3/3 | - | - | 3–7 |
Yu et al. [30] | 132/333 G1 (n=64) G2 (n=57) G3 (n=11) | 7.8 [5.0–8.2] 7.5 [5.0–7.9] 9 [5.0–8.0] | - - - | 0.5–20 0.5–23 1–14 |
Zheng et al. [45] | 61/73 | - | - | Max 26 |
Zhao et al. [46] | 6/136 | 6 [4.0–11.0] | - | 1–21 |
Zhang et al. [59] | 194 | - | 7.44 | 0.08–18 |
Xiao et al. [31] | 2555/ 4741 | - | 8.98 | - |
Wong et al. [32] | 135/135 | 5.0 | - | 1–11 |
Tan et al. [48] | 164 | 5.0 | 5.7±3.5 | 1–17 |
Nie et al. [60] | 2907/7015 | 5.0 [2.0–8.0] | - | Max 24 |
Lou et al. [50] | 45/80 | 5.0 [2.0–10.0] | - | 0–23 |
Liu et al. [62] | 58/365 | 5.0 [3.0–8.0] | 6.0 | 1–16 |
Li et al. [49] | 74/74 | 5.0 [4.0–7.0] | - | - |
Alsofayan et al. [53] | 309/1519 | 6.0 [7.5] | - | - |
Bohmer et al. [42] | 16 | 4.0 [2.3–4.3] | - | - |
You et al. [36] | 169/198 | 7.0 [4.5–10] | 8.0±4.75 | 0–23.5 |
Based on studies estimating incubation periods for SARS-CoV-2
Study | n | Distribution | Mean (days) | 95th percentile(days) | ||
---|---|---|---|---|---|---|
Estimate | 95% CI | Estimate | 95%CI | |||
Li et al. [20] | 10 | Log normal | 5.2 | 4.1–7.0 | 12.5 | 9.2–18 |
Zhang et al. [23] | 49 | Log normal | 5·2 | 1.8–12.4 | 10.5 | |
Linton et al. [29] | 52€ | Log normal* | 5.0 5.6 ┼ | 4.2–6.0 4.4–7.4 | 10.6 12.3 | 8.5–14.1 9.1–19.8 |
Weibull | 5.4 | 4.3–6.6 | 12.0 | 9.8–15.6 | ||
Gamma | 5.3 | 4.3–6.6 | 11.3 | 9.2–14.5 | ||
158€ € | Log normal* | 5.6 | 5.0–6.3 | 10.8 | 9.3–12.9 | |
Weibull | 5.8 | 5.2–6.5 | 11.0 | 9.6–12.9 | ||
Gamma | 6.0 | 5.3–6.7 | 11.7 | 10.3–13.4 | ||
Backer et al. [55] | 88 | Weibull* | 6.4 | 5.6–7.7 | 10.3 | 8.6–14.1 |
Gamma | 6.5 | 5.6–7.9 | 11.3 | 9.1–15.7 | ||
Lauer et al. [56] | 181 | Log normal* | 5.5 5.1 a | - 4.5–5.8 | 11.5b | 8.2–15.6 |
Wang et al. [57] | 483 | Log normal* | 7.4 | 2–20 | - | - |
Bi et al. [24] | 183 | Log normal | 4.8a | 4.2–5.4 | 14.0 | 12.2–15.9 |
Yu et al. [30] | 132 | Gamma | 7.2a | 6.4 -7.9 | 16.0 20.4 c | - - |
Yang et al. [26] | 178 | Weibull* | 6 a | - | 13.7 | 12.5–14.9 |
Wang et al. [47] | 14 | Log normal | 4.5 | 3.0–6.4 | 11.4 | 4.0–12.0 |
Viego et al. [33] | 12 | Log normal | 7.50 | 4.11–10.89 | - | - |
Tindale et al. [52] | 93 | Gamma | 5.99 | 4.97–7.14 | - | - |
135 | Gamma | 8.68 | 7.72–9.7 | - | - | |
Ryu et al. [34] | 181 | Log normal* | 4.7 a | 0.1–15.6 | - | - |
Qin et al(69) | 1084 | Weibull | 8.29 | 7.67–8.90 | 16.32 | 15.62-17.04 |
Lee et al. [51] | 47 | Log normal* | 3.0 a | 0.6–8.2 | - | - |
Chun et al. [9] | 74 | Weibull | 3.10 a | 2.54–3.71 | - | - |
Gamma | 2.99 a | 2.44–3.60 | - | - | ||
Log normal* | 2.87 a | 2.33–3.50 | - | - | ||
Wieland [37] | 107 | - | - | - | 5.6 b | - |
Mean incubation period and meta-analysis
Estimate | SE | 95% CI | p-value | |
---|---|---|---|---|
Intercept | 6.219 | 0.419 | (5.398; 7.041) | < 0.001 |
Population | ||||
Chinese | 6.234 | 0.507 | (5.239; 7.228) | < 0.001 |
Not Chinese | 5.790 | 0.392 | (5.022; 6.558) | < 0.001 |
Severity | ||||
Hospitalized | 6.011 | 0.448 | (5.133; 6.888) | < 0.001 |
Not hospitalized | 6.425 | 0.791 | (4.874; 7.975) | < 0.001 |
Sex ratio | ||||
>1 | 6.036 | 0.738 | (4.589; 7.483) | < 0.001 |
<1 | 5.805 | 0.435 | (4.952; 6.659) | < 0.001 |
Quality of study | ||||
Strong | 6.650 | 0.316 | (6.031; 7.269) | < 0.001 |
Moderate to weak | 6.188 | 0.419 | (5.122; 7.254) | < 0.001 |