scholarly journals Epidemiological parameters of coronavirus disease 2019: a pooled analysis of publicly reported individual data of 1155 cases from seven countries

2020 ◽  
Author(s):  
Shujuan Ma ◽  
Jiayue Zhang ◽  
Minyan Zeng ◽  
Qingping Yun ◽  
Wei Guo ◽  
...  
Keyword(s):  
Latent Period ◽  
Incubation Period ◽  
Symptom Onset ◽  
Severe Disease ◽  
Individual Data ◽  
Robust Estimates ◽  
Upper Limit ◽  
Serial Interval ◽  
Epidemiological Parameters ◽  
Time Point

SummaryBackgroundThe outbreak of coronavirus disease 2019 (COVID-19) has been declared a pandemic by the World Health Organization, while several key epidemiological parameters of the disease remain to be clarified. This study aimed to obtain robust estimates of the incubation period, upper limit of latent period (interval between infector’s exposure and infectee’s exposure), serial interval, time point of exposure (the day of infectee’s exposure to infector relative to the latter’s symptom onset date) and basic reproduction number (R0) of COVID-19.MethodsBetween late February and early March of 2020, the individual data of laboratory confirmed cases of COVID-19 were retrieved from 10728 publicly available reports released by the health authorities of and outside China and from 1790 publications identified in PubMed and CNKI. To be eligible, a report had to contain the data that allowed for estimation of at least one parameter. As relevant data mainly came from clustering cases, the clusters for which no evidence was available to establish transmission order were all excluded to ensure accuracy of estimates. Additionally, only the cases with an exposure period spanning 3 days or less were included in the estimation of parameters involving exposure date, and a simple method for determining exposure date was adopted to ensure the error of estimates be small (< 0.3 day). Depending on specific parameters, three or four of normal, lognormal, Weibull, and gamma distributions were fitted to the datasets and the results from appropriate models were presented.FindingsIn total, 1155 cases from China, Japan, Singapore, South Korea, Vietnam, Germany and Malaysia were included for the final analysis. The mean and standard deviation were 7.44 days and 4.39 days for incubation period, 2.52 days and 3.95 days for the upper limit of latent period, 6.70 days and 5.20 days for serial interval, and −0.19 day (i.e., 0.19 day before infector’s symptom onset) and 3.32 days for time point of exposure. R0 was estimated to be 1.70 and 1.78 based on two different formulas. For 39 (6.64%) cases, the incubation periods were longer than 14 days. In 102 (43.78%) infector-infectee pairs, transmission occurred before infectors’ symptom onsets. In 27 (3.92%) infector-infectee pairs, infectees’ symptom onsets occurred before those of infectors. Stratified analysis showed that incubation period and serial interval were consistently longer for those with less severe disease and for those whose primary cases had less severe disease. Asymptomatic transmission was also observed.InterpretationThis study obtained robust estimates of several key epidemiological parameters of COVID-19. The findings support current practice of 14-day quarantine of persons with potential exposure, but also suggest that longer monitoring periods might be needed for selected groups. The estimates of serial interval, time point of exposure and latent period provide consistent evidence on pre-symptomatic transmission. This together with asymptomatic transmission and the generally longer incubation and serial interval of less severe cases suggests a high risk of long-term epidemic in the absence of appropriate control measures.FundingThis work received no funding from any source.

scholarly journals Epidemiological Parameters of COVID-19: Case Series Study

10.2196/19994 ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. e19994
Author(s):  
Shujuan Ma ◽  
Jiayue Zhang ◽  
Minyan Zeng ◽  
Qingping Yun ◽  
Wei Guo ◽  
...  
Keyword(s):  
Incubation Period ◽  
Case Series ◽  
Final Analysis ◽  
Small Sample ◽  
Accurate Estimation ◽  
China National Knowledge Infrastructure ◽  
Robust Estimates ◽  
Serial Interval ◽  
Case Series Study ◽  
Epidemiological Parameters

Background The estimates of several key epidemiological parameters of the COVID-19 pandemic are often based on small sample sizes or are inaccurate for various reasons. Objective The aim of this study is to obtain more robust estimates of the incubation period, serial interval, frequency of presymptomatic transmission, and basic reproduction number (R0) of COVID-19 based on a large case series. Methods We systematically retrieved and screened 20,658 reports of laboratory-confirmed COVID-19 cases released by the health authorities of China, Japan, and Singapore. In addition, 9942 publications were retrieved from PubMed and China National Knowledge Infrastructure (CNKI) through April 8, 2020. To be eligible, a report had to contain individual data that allowed for accurate estimation of at least one parameter. Widely used models such as gamma distributions were fitted to the data sets and the results with the best-fitting values were presented. Results In total, 1591 cases were included for the final analysis. The mean incubation period (n=687) and mean serial interval (n=1015 pairs) were estimated to be 7.04 (SD 4.27) days and 6.49 (SD 4.90) days, respectively. In 40 cases (5.82%), the incubation period was longer than 14 days. In 32 infector-infectee pairs (3.15%), infectees’ symptom onsets occurred before those of infectors. Presymptomatic transmission occurred in 129 of 296 infector-infectee pairs (43.58%). R0 was estimated to be 1.85 (95% CI 1.37-2.60). Conclusions This study provides robust estimates of several epidemiological parameters of COVID-19. The findings support the current practice of 14-day quarantine of persons with potential exposure, but also suggest the need for additional measures. Presymptomatic transmission together with the asymptomatic transmission reported by previous studies highlight the importance of adequate testing, strict quarantine, and social distancing.

scholarly journals Epidemiological Parameters of COVID-19: Case Series Study (Preprint)

2020 ◽  
Author(s):  
Shujuan Ma ◽  
Jiayue Zhang ◽  
Minyan Zeng ◽  
Qingping Yun ◽  
Wei Guo ◽  
...  
Keyword(s):  
Incubation Period ◽  
Case Series ◽  
Final Analysis ◽  
Small Sample ◽  
Accurate Estimation ◽  
China National Knowledge Infrastructure ◽  
Robust Estimates ◽  
Serial Interval ◽  
Case Series Study ◽  
Epidemiological Parameters

BACKGROUND The estimates of several key epidemiological parameters of the COVID-19 pandemic are often based on small sample sizes or are inaccurate for various reasons. OBJECTIVE The aim of this study is to obtain more robust estimates of the incubation period, serial interval, frequency of presymptomatic transmission, and basic reproduction number (R<sub>0</sub>) of COVID-19 based on a large case series. METHODS We systematically retrieved and screened 20,658 reports of laboratory-confirmed COVID-19 cases released by the health authorities of China, Japan, and Singapore. In addition, 9942 publications were retrieved from PubMed and China National Knowledge Infrastructure (CNKI) through April 8, 2020. To be eligible, a report had to contain individual data that allowed for accurate estimation of at least one parameter. Widely used models such as gamma distributions were fitted to the data sets and the results with the best-fitting values were presented. RESULTS In total, 1591 cases were included for the final analysis. The mean incubation period (n=687) and mean serial interval (n=1015 pairs) were estimated to be 7.04 (SD 4.27) days and 6.49 (SD 4.90) days, respectively. In 40 cases (5.82%), the incubation period was longer than 14 days. In 32 infector-infectee pairs (3.15%), infectees’ symptom onsets occurred before those of infectors. Presymptomatic transmission occurred in 129 of 296 infector-infectee pairs (43.58%). R<sub>0</sub> was estimated to be 1.85 (95% CI 1.37-2.60). CONCLUSIONS This study provides robust estimates of several epidemiological parameters of COVID-19. The findings support the current practice of 14-day quarantine of persons with potential exposure, but also suggest the need for additional measures. Presymptomatic transmission together with the asymptomatic transmission reported by previous studies highlight the importance of adequate testing, strict quarantine, and social distancing.

scholarly journals Association between incubation period and clinical characteristics of patients with COVID-19

2020 ◽  
Vol 48 (9) ◽  
pp. 030006052095683
Author(s):  
Yeyu Cai ◽  
Jiayi Liu ◽  
Haitao Yang ◽  
Mian Wang ◽  
Qingping Guo ◽  
...  
Keyword(s):  
Incubation Period ◽  
Disease Severity ◽  
Symptom Onset ◽  
Clinical Characteristics ◽  
Characteristic Curve ◽  
Severe Disease ◽  
Receiver Operator Characteristic Curve ◽  
Hunan Province ◽  
Laboratory Findings ◽  
Incubation Periods

Purpose To investigate associations between the clinical characteristics and incubation periods of patients infected with coronavirus disease 2019 (COVID-19) in Wuhan, China. Methods Complete clinical and epidemiological data from 149 patients with COVID-19 at a hospital in Hunan Province, China, were collected and retrospectively analyzed. Results Analysis of the distribution and receiver operator characteristic curve of incubation periods showed that 7 days was the optimal cut-off value to assess differences in disease severity between groups. Patients with shorter (≤7 days) incubation periods (n = 79) had more severe disease, longer durations of hospitalization, longer times from symptom onset to discharge, more abnormal laboratory findings, and more severe radiological findings than patients with longer (>7 days) incubation periods. Regression and correlation analyses also showed that a shorter incubation period was associated with longer times from symptom onset to discharge. Conclusion The associations between the incubation periods and clinical characteristics of COVID-19 patients suggest that the incubation period may be a useful marker of disease severity and prognosis.

scholarly journals Estimating the presymptomatic transmission of COVID19 using incubation period and serial interval data

2020 ◽  
Author(s):  
Weituo Zhang
Keyword(s):  
Mathematical Models ◽  
Incubation Period ◽  
Symptom Onset ◽  
Interval Data ◽  
Serial Interval ◽  
Imported Cases

AbstractWe estimated the fraction and timing of presymptomatic transmissions of COVID19 with mathematical models combining the available data of the incubation period and serial interval. We found that up to 79.7% transmissions could be presymptomatic among the imported cases in China outside Wuhan. The average timing of presymptomatic transmissions is 3.8 days (SD = 6.1) before the symptom onset, which is much earlier than previously assumed.

scholarly journals Epidemiological parameters of COVID-19 and its implication for infectivity among patients in China, 1 January to 11 February 2020

2020 ◽  
Vol 25 (40) ◽  
Author(s):  
Qing-Bin Lu ◽  
Yong Zhang ◽  
Ming-Jin Liu ◽  
Hai-Yang Zhang ◽  
Neda Jalali ◽  
...  
Keyword(s):  
Incubation Period ◽  
Symptom Onset ◽  
Age Groups ◽  
Control Measures ◽  
Adult Age ◽  
Secondary Infections ◽  
History Of ◽  
Early Case ◽  
Relative Infectivity ◽  
Epidemiological Parameters

Background The natural history of disease in patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remained obscure during the early pandemic. Aim Our objective was to estimate epidemiological parameters of coronavirus disease (COVID-19) and assess the relative infectivity of the incubation period. Methods We estimated the distributions of four epidemiological parameters of SARS-CoV-2 transmission using a large database of COVID-19 cases and potential transmission pairs of cases, and assessed their heterogeneity by demographics, epidemic phase and geographical region. We further calculated the time of peak infectivity and quantified the proportion of secondary infections during the incubation period. Results The median incubation period was 7.2 (95% confidence interval (CI): 6.9‒7.5) days. The median serial and generation intervals were similar, 4.7 (95% CI: 4.2‒5.3) and 4.6 (95% CI: 4.2‒5.1) days, respectively. Paediatric cases < 18 years had a longer incubation period than adult age groups (p = 0.007). The median incubation period increased from 4.4 days before 25 January to 11.5 days after 31 January (p < 0.001), whereas the median serial (generation) interval contracted from 5.9 (4.8) days before 25 January to 3.4 (3.7) days after. The median time from symptom onset to discharge was also shortened from 18.3 before 22 January to 14.1 days after. Peak infectivity occurred 1 day before symptom onset on average, and the incubation period accounted for 70% of transmission. Conclusion The high infectivity during the incubation period led to short generation and serial intervals, necessitating aggressive control measures such as early case finding and quarantine of close contacts.

scholarly journals Transmission onset distribution of COVID-19

2020 ◽  
Author(s):  
June Young Chun ◽  
Gyuseung Baek ◽  
Yongdai Kim
Keyword(s):  
Standard Deviation ◽  
Incubation Period ◽  
Bayesian Methods ◽  
Symptom Onset ◽  
Onset Time ◽  
Preventive Measure ◽  
Credible Interval ◽  
Serial Interval ◽  
Interval Distribution ◽  
Key Parameter

AbstractObjectivesThe distribution of the transmission onset of COVID-19 relative to the symptom onset is a key parameter for infection control. It is often not easy to study the transmission onset time, as is difficult to know who infected whom exactly when.MethodsWe inferred transmission onset time from 72 infector-infectee pairs in South Korea, either with known or inferred contact dates by means of incubation period. Combining this data with known information of infector’s symptom onset, we could generate the transmission onset distribution of COVID-19, using Bayesian methods. Serial interval distribution could be automatically estimated from our data.ResultsWe estimated the median transmission onset to be 1.31 days (standard deviation, 2.64 days) after symptom onset with peak at 0.72 days before symptom onset. The pre-symptomatic transmission proportion was 37% (95% credible interval [CI], 16–52%). The median incubation period was estimated to be 2.87 days (95% CI, 2.33–3.50 days) and the median serial interval to be 3.56 days (95% CI, 2.72–4.44 days).ConclusionsConsidering the transmission onset distribution peaked with the symptom onset and the pre-symptomatic transmission proportion is substantial, the usual preventive measure might be too late to prevent SARS-CoV-2 transmission.

scholarly journals Estimating the generation interval for COVID-19 based on symptom onset data

2020 ◽  
Author(s):  
Ganyani Tapiwa ◽  
Kremer Cécile ◽  
Chen Dongxuan ◽  
Torneri Andrea ◽  
Faes Christel ◽  
...  
Keyword(s):  
Incubation Period ◽  
Symptom Onset ◽  
Contact Tracing ◽  
Transmission Network ◽  
Generation Interval ◽  
Period Distribution ◽  
Reproduction Numbers ◽  
Serial Interval ◽  
Modelling Studies ◽  
Interval Distribution

AbstractBackgroundEstimating key infectious disease parameters from the COVID-19 outbreak is quintessential for modelling studies and guiding intervention strategies. Whereas different estimates for the incubation period distribution and the serial interval distribution have been reported, estimates of the generation interval for COVID-19 have not been provided.MethodsWe used outbreak data from clusters in Singapore and Tianjin, China to estimate the generation interval from symptom onset data while acknowledging uncertainty about the incubation period distribution and the underlying transmission network. From those estimates we obtained the proportions pre-symptomatic transmission and reproduction numbers.ResultsThe mean generation interval was 5.20 (95%CI 3.78-6.78) days for Singapore and 3.95 (95%CI 3.01-4.91) days for Tianjin, China when relying on a previously reported incubation period with mean 5.2 and SD 2.8 days. The proportion of pre-symptomatic transmission was 48% (95%CI 32-67%) for Singapore and 62% (95%CI 50-76%) for Tianjin, China. Estimates of the reproduction number based on the generation interval distribution were slightly higher than those based on the serial interval distribution.ConclusionsEstimating generation and serial interval distributions from outbreak data requires careful investigation of the underlying transmission network. Detailed contact tracing information is essential for correctly estimating these quantities.

scholarly journals Incubation period of COVID-19 in the “live-house” cluster of accurately known infection events and delay time from symptom onset of public reporting observed in cases in Osaka, Japan

2020 ◽  
Author(s):  
Toshihisa Tomie
Keyword(s):  
Infectious Disease ◽  
Latent Period ◽  
Incubation Period ◽  
Symptom Onset ◽  
Delay Time ◽  
Public Reporting ◽  
Period Distribution

AbstractThe incubation period of an infectious disease is very important for control of the disease but estimating the period is not easy because the date of infection is not easy to identify. Accurate incubation period distribution by examining cases in the cluster generated in “live-houses” in Osaka, Japan with known infection events is reported. The distribution of the latent period is also estimated. The modes of incubation and latent periods of COVID-19 in Japan are 4.1 days and 3.3 days, respectively. The mode of the delay time from the onset to reporting is estimated to be 4.7 days, telling that the effects of interventions show up in the number of infections two weeks later after the measures.

scholarly journals SAT0253 ANTI-NEUTROPHIL CYTOPLASMATIC ANTIBODIES PREDATE SYMPTOM ONSET OF ANCA-ASSOCIATED VASCULITIS. A CASE-CONTROL STUDY

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 1069.2-1070
Author(s):  
E. Berglin ◽  
A. J. Mohammad ◽  
J. Dahlqvist ◽  
C. Eriksson ◽  
J. Sjöwall ◽  
...  
Keyword(s):  
Cause Of Death ◽  
Symptom Onset ◽  
Severe Disease ◽  
Disease Onset ◽  
Control Sample ◽  
Discharge Summary ◽  
Serum Samples ◽  
Blood Samples ◽  
Anca Associated Vasculitis ◽  
Time Point

Background:Presence of anti-neutrophil cytoplasmatic autoantibodies (ANCA) is important for the diagnosis of ANCA-associated vasculitis (AAV) and reflects on-going immune processes. The timing of the antibody development and its contribution to disease is not well established.Objectives:To investigate the presence of proteinase 3 (PR3)- and myeloperoxidase (MPO)-ANCA in blood samples collected from healthy individuals who subsequently developed AAV.Methods:The Swedish National Patient Register of inpatient care and the Swedish Cause of Death Register were used to identify individuals assigned ICD codes for AAV (1) in the discharge summary or cause of death, respectively. The resulted cohort was then linked to the registers of 4 different biobanks to identify those with available predating blood samples. Diagnoses of AAV were confirmed and time point for onset of symptoms was identified by reviewing all available case records (1); 68 were classified as granulomatosis with polyangiitis (GPA), 14 as microscopic polyangiitis (MPA), and 4 as eosinophilic GPA (EGPA). The 86 cases (36 males, 50 females) had a mean (SD) age of 51.9 (16.9) years at sampling, with ≥1 sample (26% plasma, 74% serum samples). The sampling time point before onset of symptoms was mean (SD); 4.4 (3.1) years. Serum and plasma control samples (n=198; 82 males, 116 females; mean age (SD); 52.0 (16.5) years) were identified and matched for sex, age and date of sampling. The samples were first screened for ANCA using high sensitive ELISA (ORGANTEC diagnostika, Germany) and samples close to or above cut-off level were further analysed for capture PR3- and capture MPO-ANCA (ELISA; SVAR Life Science, Sweden). For each case one control sample was included for the ANCA specificity tests. Statistical calculations were performed using SPSS software.Results:In ANCA-screen 36.0% of the cases and 2.6 % of controls tested positive (p<0.001). 23/52 (44.2%) of the cases were PR3-ANCA positive (OR 56.3; 95% CI 7.26-436.62) and 8/52 (15.4%) were MPO-ANCA positive (OR 4.18; 95% CI 1.05-16.62). The mean (SD) predating time for PR3-ANCA positivity was 3.73 (3.49) years and for MPO-ANCA positivity 2.11 (1.46) years. Cases with positive predating PR3-ANCA were younger (46.0±19.4 vs 65.6±12.0 years; P<0.001) than cases with a negative predating PR3-ANCA. MPO-ANCA positive vs. MPO-ANCA negative pre-dating cases had more often severe disease (kidney/lung/peripheral nervous system) (OR 15.08; 95% CI 1.68—135.54) at disease onset. Furthermore, predating MPO-ANCA positive vs predating PR3-ANCA positive cases had significantly more often severe manifestations at disease onset (87.5% vs 28.6%; p<0.05). Cases positive vs. negative for MPO-ANCA in predating samples were less often classified as GPA (37.5% vs 86.4%; p<0.01) and more often as MPA (62.5% vs 13.6%; p<0.05).Conclusion:The production of both PR3 and MPO-ANCA starts already years before onset of symptoms of AAV. Presence of MPO-ANCA appeared closer to symptom onset and with more severe disease presentation. Differences in the disease phenotype and disease severity were evident between the two ANCA serotypes.References:[1]Watts et al. Ann Rheum Dis 2007;66:222-22Acknowledgments: :Vasculitis Foundation, USADisclosure of Interests:Ewa Berglin: None declared, Aladdin J Mohammad Speakers bureau: lecture fees from Roche and Elli Lilly Sweden, PI (GiACTA study), Johanna Dahlqvist: None declared, Catharina Eriksson: None declared, Johanna Sjöwall: None declared, Solbritt Rantapää Dahlqvist: None declared

scholarly journals Transmission of corona virus disease 2019 during the incubation period may lead to a quarantine loophole

2020 ◽  
Author(s):  
Wei Xia ◽  
Jiaqiang Liao ◽  
Chunhui Li ◽  
Yuanyuan Li ◽  
Xi Qian ◽  
...  
Keyword(s):  
Incubation Period ◽  
Symptom Onset ◽  
First Generation ◽  
Virus Disease ◽  
Demographic Characteristics ◽  
Corona Virus ◽  
Serial Interval ◽  
History Of ◽  
Exposure History ◽  
Close Contacts

AbstractBackgroundThe ongoing outbreak of novel corona virus disease 2019 (COVID-19) in Wuhan, China, is arousing international concern. This study evaluated whether and when the infected but asymptomatic cases during the incubation period could infect others.MethodsWe collected data on demographic characteristics, exposure history, and symptom onset day of the confirmed cases, which had been announced by the Chinese local authorities. We evaluated the potential of transmission during the incubation period in 50 infection clusters, including 124 cases. All the secondary cases had a history of contact with their first-generation cases prior to symptom onset.ResultsThe estimated mean incubation period for COVID-19 was 4.9 days (95% confidence interval [CI], 4.4 to 5.4) days, ranging from 0.8 to 11.1 days (2.5th to 97.5th percentile). The observed mean and standard deviation (SD) of serial interval was 4.1±3.3 days, with the 2.5th and 97.5th percentiles at −1 and 13 days. The infectious curve showed that in 73.0% of the secondary cases, their date of getting infected was before symptom onset of the first-generation cases, particularly in the last three days of the incubation period.ConclusionsThe results indicated the transmission of COVID-9 occurs among close contacts during the incubation period, which may lead to a quarantine loophole. Strong and effective countermeasures should be implemented to prevent or mitigate asymptomatic transmission during the incubation period in populations at high risk.

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