Rapid review of available evidence on the serial interval and generation
                        time of COVID-19

The serial interval is the time between symptom onsets in an infector–infectee pair. The generation time, also known as the generation interval, is the time between infection events in an infector–infectee pair. The serial interval and the generation time are key parameters for assessing the dynamics of a disease. A number of scientific papers reported information pertaining to the serial interval and/or generation time for COVID-19. Objective Conduct a review of available evidence to advise on appropriate parameter values for serial interval and generation time in national COVID-19 transmission models for Ireland and on methodological issues relating to those parameters. Methods We conducted a rapid review of the literature covering the period 1 January 2020 and 21 August 2020, following predefined eligibility criteria. Forty scientific papers met our inclusion criteria and were included in the review. Results The mean of the serial interval ranged from 3.03 to 7.6 days, based on 38 estimates, and the median from 1.0 to 6.0 days (based on 15 estimates). Only three estimates were provided for the mean of the generation time. These ranged from 3.95 to 5.20 days. One estimate of 5.0 days was provided for the median of the generation time. Discussion Estimates of the serial interval and the generation time are very dependent on the specific factors that apply at the time that the data are collected, including the level of social contact. Consequently, the estimates may not be entirely relevant to other environments. Therefore, local estimates should be obtained as soon as possible. Careful consideration should be given to the methodology that is used. Real-time estimations of the serial interval/generation time, allowing for variations over time, may provide more accurate estimates of reproduction numbers than using conventionally fixed serial interval/generation time distributions.

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A rapid review of available evidence on the serial interval and generation time of COVID-19

10.1101/2020.05.08.20095075 ◽

2020 ◽

Cited By ~ 10

Author(s):

John Griffin ◽

Áine B. Collins ◽

Kevin Hunt ◽

Miriam Casey ◽

David Mc Evoy ◽

...

Keyword(s):

Generation Time ◽

Scientific Literature ◽

Control Measures ◽

Mitigation Measures ◽

Rapid Review ◽

List Type ◽

Interval Estimate ◽

Serial Interval ◽

Scientific Papers ◽

The Mean

AbstractBackgroundThe serial interval is the time between symptom onsets in an infector-infectee pair. The generation time, also known as the generation interval, is the time between infection events in an infector-infectee pair. The serial interval and the generation time are key parameters for assessing the dynamics of a disease. A number of scientific papers reported information pertaining to the serial interval and/or generation time for COVID-19.ObjectivesConduct a rapid review of available evidence to advise on appropriate parameter values for serial interval and generation time in national COVID-19 transmission models for Ireland and on methodological issues relating to those parameters.MethodsA review of scientific literature was conducted covering the period between December 1, 2019 and April 27, 2020. Nineteen scientific papers were evaluated in detail from 27 papers that contained information on the serial interval and/or generation time for COVID-19.ResultsThe mean of the serial interval ranged from 3.1 to 7.5 days, based on 22 estimates, and the median from 1.9 to 6.0 days (based on 7 estimates). Only three estimates were provided for the mean of the generation time. These ranged from 3.9 to 5.2 days. One estimate of 5.0 days was provided for the median of the generation time.DiscussionThe values of the estimates for serial interval and generation time are heavily influenced by the contact rates between infectious and susceptible individuals. Mitigation measures that are introduced in a country or region are of paramount importance in this regard. The serial interval estimate of 6.6 days (95% confidence interval: 0.7 – 19.0) from the paper by Cereda et al.[10] is likely to be the most relevant to European countries. National estimates should be obtained as soon as possible.Strengths and limitations of this studyThe study provides timely information on serial interval and generation time for those involved in the development of models and in the implementation of control measures against COVID-19.This is a rapid review of available evidence in the scientific literature between December 1, 2019 and April 27, 2020 on the serial interval and/or the generation time and it contains the usual limitations associated with such a review.Eleven of the 19 papers reviewed in detail were pre-print articles.The statistical methods used in the different papers were not analysed in detail.

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Presymptomatic transmission of SARS-CoV-2 infection: a secondary analysis using published data

BMJ Open ◽

10.1136/bmjopen-2020-041240 ◽

2021 ◽

Vol 11 (6) ◽

pp. e041240

Author(s):

Miriam Casey-Bryars ◽

John Griffin ◽

Conor McAloon ◽

Andrew Byrne ◽

Jamie Madden ◽

...

Keyword(s):

Incubation Period ◽

Symptom Onset ◽

Generation Time ◽

Meta Analysis ◽

Secondary Analysis ◽

Transmission Time ◽

Contact Tracing ◽

Rapid Review ◽

Published Data ◽

Serial Interval

ObjectiveTo estimate the proportion of presymptomatic transmission of SARS-CoV-2 infection that can occur, and the timing of transmission relative to symptom onset.Setting/designSecondary analysis of international published data.Data sourcesMeta-analysis of COVID-19 incubation period and a rapid review of serial interval and generation time, which are published separately.ParticipantsData from China, the Islamic Republic of Iran, Italy, Republic of Korea, Singapore and Vietnam from December 2019 to May 2020.MethodsSimulations were generated of incubation period and of serial interval or generation time. From these, transmission times relative to symptom onset, and the proportion of presymptomatic transmission, were estimated.Outcome measuresTransmission time of SARS-CoV-2 relative to symptom onset and proportion of presymptomatic transmission.ResultsBased on 18 serial interval/generation time estimates from 15 papers, mean transmission time relative to symptom onset ranged from −2.6 (95% CI −3.0 to –2.1) days before infector symptom onset to 1.4 (95% CI 1.0 to 1.8) days after symptom onset. The proportion of presymptomatic transmission ranged from 45.9% (95% CI 42.9% to 49.0%) to 69.1% (95% CI 66.2% to 71.9%).ConclusionsThere is substantial potential for presymptomatic transmission of SARS-CoV-2 across a range of different contexts. This highlights the need for rapid case detection, contact tracing and quarantine. The transmission patterns that we report reflect the combination of biological infectiousness and transmission opportunities which vary according to context.

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Drain fluid cryo-explant technique for treatment of superior bullous rhegmatogenous retinal detachment in young adults

Therapeutic Advances in Ophthalmology ◽

10.1177/2515841420988211 ◽

2021 ◽

Vol 13 ◽

pp. 251584142098821

Author(s):

Kamal A.M. Solaiman ◽

Ashraf Mahrous ◽

Hesham A. Enany ◽

Ashraf Bor’i

Keyword(s):

Young Adults ◽

Retinal Detachment ◽

Rhegmatogenous Retinal Detachment ◽

Subretinal Fluid ◽

Secondary Outcome ◽

Eligibility Criteria ◽

Retinal Breaks ◽

Complicated Cataract ◽

Drain Fluid ◽

The Mean

Purpose: To evaluate the efficacy of the drain fluid cryo-explant (DFCE) technique for the management of uncomplicated superior bullous rhegmatogenous retinal detachment (RRD) in young adults. Patients and methods: A retrospective study that included eyes with uncomplicated superior bullous RRD in patients ⩽40 years old. DFCE technique consists of sequential drainage of subretinal fluid, intravitreal fluid injection, cryotherapy, and placement of a scleral explant(s). The primary outcome measure was anatomical reposition of the retina after a single surgery. Secondary outcome measures included improvement in best corrected visual acuity (BCVA) and any reported complication related to the procedure. Results: The study included 51 eyes which met the study eligibility criteria. The mean duration of detachment was 19.7 ± 6.4 days. A single retinal break was found in 31 eyes (60.8%), and more than one break were found in 20 eyes (39.2%). The mean number of breaks per eye was 1.72 ± 1.04. The mean detached area per eye was 7.21 ± 3.19 clock hours, and the macula was detached in 22 eyes (43.1%). Flattening of the retina and closure of all retinal breaks was achieved in all eyes after a single surgery. Late recurrence of retinal detachment occurred in two eyes (3.9%) due to proliferative vitreoretinopathy (PVR). No complicated cataract or iatrogenic retinal breaks were detected in all eyes. Conclusion: DFCE technique could be effectively used for treatment of uncomplicated superior bullous RRD in adults ⩽40 years. It is safe and provides good visualization during surgery with no iatrogenic retinal breaks or complicated cataract.

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Measuring frailty in younger populations: a rapid review of evidence

BMJ Open ◽

10.1136/bmjopen-2020-047051 ◽

2021 ◽

Vol 11 (3) ◽

pp. e047051

Author(s):

Gemma F Spiers ◽

Tafadzwa Patience Kunonga ◽

Alex Hall ◽

Fiona Beyer ◽

Elisabeth Boulton ◽

...

Keyword(s):

Patient Outcomes ◽

Predictive Validity ◽

Data Extraction ◽

Grey Literature ◽

Frailty Index ◽

Study Data ◽

Rapid Review ◽

Eligibility Criteria ◽

Adult Age ◽

The Impact

ObjectivesFrailty is typically assessed in older populations. Identifying frailty in adults aged under 60 years may also have value, if it supports the delivery of timely care. We sought to identify how frailty is measured in younger populations, including evidence of the impact on patient outcomes and care.DesignA rapid review of primary studies was conducted.Data sourcesFour databases, three sources of grey literature and reference lists of systematic reviews were searched in March 2020.Eligibility criteriaEligible studies measured frailty in populations aged under 60 years using experimental or observational designs, published after 2000 in English.Data extraction and synthesisRecords were screened against review criteria. Study data were extracted with 20% of records checked for accuracy by a second researcher. Data were synthesised using a narrative approach.ResultsWe identified 268 studies that measured frailty in samples that included people aged under 60 years. Of these, 85 studies reported evidence about measure validity. No measures were identified that were designed and validated to identify frailty exclusively in younger groups. However, in populations that included people aged over and under 60 years, cumulative deficit frailty indices, phenotype measures, the FRAIL Scale, the Liver Frailty Index and the Short Physical Performance Battery all demonstrated predictive validity for mortality and/or hospital admission. Evidence of criterion validity was rare. The extent to which measures possess validity across the younger adult age (18–59 years) spectrum was unclear. There was no evidence about the impact of measuring frailty in younger populations on patient outcomes and care.ConclusionsLimited evidence suggests that frailty measures have predictive validity in younger populations. Further research is needed to clarify the validity of measures across the adult age spectrum, and explore the utility of measuring frailty in younger groups.

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Identifying enablers and barriers to referral, uptake and completion of lifestyle modification programmes: a rapid literature review

BMJ Open ◽

10.1136/bmjopen-2020-045094 ◽

2021 ◽

Vol 11 (3) ◽

pp. e045094

Author(s):

Yvonne Zurynski ◽

Carolynn Smith ◽

Joyce Siette ◽

Bróna Nic Giolla Easpaig ◽

Mary Simons ◽

...

Keyword(s):

Chronic Disease ◽

Lifestyle Modification ◽

Data Extraction ◽

Empirical Studies ◽

Grey Literature ◽

International Health ◽

Rapid Review ◽

Eligibility Criteria ◽

Relevant Evidence ◽

Literature Reviews

ObjectiveTo identify current, policy-relevant evidence about barriers and enablers associated with referral, uptake and completion of lifestyle modification programmes (LMPs) for secondary prevention of chronic disease in adults.DesignA rapid review, co-designed with policymakers, of peer-reviewed and grey literature using a modified Preferred Reporting Items for Systematic Reviews and Meta-Analyses framework.Data sourcesMedline, Embase, Scopus, PsycINFO and CINAHL were searched for relevant studies and literature reviews. Grey literature was identified through Advanced Google searching and targeted searching of international health departments’ and non-government organisations’ websites.Eligibility criteria for selecting studiesDocuments published 2010–2020, from high-income countries, reporting on programmes that included referral of adults with chronic disease to an LMP by a health professional (HP).Data extraction and synthesisData from grey and peer-reviewed literature were extracted by two different reviewers. Extracted data were inductively coded around emergent themes. Regular meetings of the review group ensured consistency of study selection and synthesis.ResultsTwenty-nine documents were included: 14 grey literature, 11 empirical studies and four literature reviews. Key barriers to HPs referring patients included inadequate HP knowledge about LMPs, perceptions of poor effectiveness of LMPs and perceptions that referral to LMPs was not part of their role. Patient barriers to uptake and completion included poor accessibility and lack of support to engage with the LMPs. Enablers to HP referral included training/education, effective interdisciplinary communication and influential programme advocates. Support to engage with LMPs after HP referral, educational resources for family members and easy accessibility were key enablers to patient engagement with LMPs.ConclusionsFactors related to HPs’ ability and willingness to make referrals are important for the implementation of LMPs, and need to be coupled with support for patients to engage with programmes after referral. These factors should be addressed when implementing LMPs to maximise their impact.

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Partial pulpotomy without age restriction: a retrospective assessment of permanent teeth with carious pulp exposure

Clinical Oral Investigations ◽

10.1007/s00784-021-04007-2 ◽

2021 ◽

Author(s):

Florin Eggmann ◽

Thomas J. W. Gasser ◽

Hanjo Hecker ◽

Mauro Amato ◽

Roland Weiger ◽

...

Keyword(s):

Survival Rates ◽

Age Groups ◽

Permanent Teeth ◽

Eligibility Criteria ◽

Presumptive Diagnosis ◽

Tooth Discoloration ◽

Significant Difference ◽

Pulp Exposure ◽

The Mean

Abstract Objectives This study aimed to retrospectively evaluate clinical and radiographic outcomes of partial pulpotomy performed in permanent teeth with carious pulp exposure. Materials and methods Records of patients undergoing treatment at an undergraduate dental clinic between 2010 and 2019 were screened for partial pulpotomies in teeth with a presumptive diagnosis of normal pulp or reversible pulpitis. The follow-up had to be ≥ 1 year. Patient data were retrieved and analyzed using Mantel-Cox chi square tests and Kaplan–Meier statistics. The level of significance was set at α = 0.05. Results Partial pulpotomy was performed in 111 cases, of which 64 (58%) fulfilled the eligibility criteria. At the time of partial pulpotomy, the mean age was 37.3 (± 13.5) years (age range 18–85). The mean observation period was 3.1 (± 2.0) years. Two early failures (3.1%) and five late failures (7.7%) were recorded. The overall success rate of maintaining pulp vitality was 89.1%, with 98.4% tooth survival. The cumulative pulp survival rates of partial pulpotomy in patients aged < 30 years, between 30 and 40 years, and > 40 years were 100%, 75.5%, and 90.5%, respectively, with no significant difference between the age groups (p = 0.225). At follow-up, narrowing of the pulp canal space and tooth discoloration were observed in 10.9% and 3.1% of cases, respectively. Conclusions Across age groups, partial pulpotomy achieved favorable short and medium-term outcomes in teeth with carious pulp exposure. Clinical relevance Adequate case selection provided, partial pulpotomy is a viable operative approach to treat permanent teeth with deep carious lesions irrespective of patients’ age.

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Subcritical Transmission in the Early Stage of COVID-19 in Korea

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18031265 ◽

2021 ◽

Vol 18 (3) ◽

pp. 1265

Author(s):

Yong Sul Won ◽

Jong-Hoon Kim ◽

Chi Young Ahn ◽

Hyojung Lee

Keyword(s):

Incubation Period ◽

Early Stage ◽

Probability Distributions ◽

Likelihood Estimation ◽

Contact Tracing ◽

Statistical Characterization ◽

Serial Interval ◽

Imported Cases ◽

The Mean ◽

Reporting Delays

While the coronavirus disease 2019 (COVID-19) outbreak has been ongoing in Korea since January 2020, there were limited transmissions during the early stages of the outbreak. In the present study, we aimed to provide a statistical characterization of COVID-19 transmissions that led to this small outbreak. We collated the individual data of the first 28 confirmed cases reported from 20 January to 10 February 2020. We estimated key epidemiological parameters such as reporting delay (i.e., time from symptom onset to confirmation), incubation period, and serial interval by fitting probability distributions to the data based on the maximum likelihood estimation. We also estimated the basic reproduction number (R0) using the renewal equation, which allows for the transmissibility to differ between imported and locally transmitted cases. There were 16 imported and 12 locally transmitted cases, and secondary transmissions per case were higher for the imported cases than the locally transmitted cases (nine vs. three cases). The mean reporting delays were estimated to be 6.76 days (95% CI: 4.53, 9.28) and 2.57 days (95% CI: 1.57, 4.23) for imported and locally transmitted cases, respectively. The mean incubation period was estimated to be 5.53 days (95% CI: 3.98, 8.09) and was shorter than the mean serial interval of 6.45 days (95% CI: 4.32, 9.65). The R0 was estimated to be 0.40 (95% CI: 0.16, 0.99), accounting for the local and imported cases. The fewer secondary cases and shorter reporting delays for the locally transmitted cases suggest that contact tracing of imported cases was effective at reducing further transmissions, which helped to keep R0 below one and the overall transmissions small.

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Infarcted Left Ventricles Have Stiffer Material Properties and Lower Stiffness Variation: Three-Dimensional Echo-Based Modeling to Quantify In Vivo Ventricle Material Properties

Journal of Biomechanical Engineering ◽

10.1115/1.4030668 ◽

2015 ◽

Vol 137 (8) ◽

Cited By ~ 8

Author(s):

Longling Fan ◽

Jing Yao ◽

Chun Yang ◽

Dalin Tang ◽

Di Xu

Keyword(s):

Wall Thickness ◽

Material Properties ◽

Strain Curve ◽

Stress And Strain ◽

Stress Strain ◽

Material Stiffness ◽

The Mean ◽

Lv Volume ◽

Parameter Values

Methods to quantify ventricle material properties noninvasively using in vivo data are of great important in clinical applications. An ultrasound echo-based computational modeling approach was proposed to quantify left ventricle (LV) material properties, curvature, and stress/strain conditions and find differences between normal LV and LV with infarct. Echo image data were acquired from five patients with myocardial infarction (I-Group) and five healthy volunteers as control (H-Group). Finite element models were constructed to obtain ventricle stress and strain conditions. Material stiffening and softening were used to model ventricle active contraction and relaxation. Systolic and diastolic material parameter values were obtained by adjusting the models to match echo volume data. Young's modulus (YM) value was obtained for each material stress–strain curve for easy comparison. LV wall thickness, circumferential and longitudinal curvatures (C- and L-curvature), material parameter values, and stress/strain values were recorded for analysis. Using the mean value of H-Group as the base value, at end-diastole, I-Group mean YM value for the fiber direction stress–strain curve was 54% stiffer than that of H-Group (136.24 kPa versus 88.68 kPa). At end-systole, the mean YM values from the two groups were similar (175.84 kPa versus 200.2 kPa). More interestingly, H-Group end-systole mean YM was 126% higher that its end-diastole value, while I-Group end-systole mean YM was only 29% higher that its end-diastole value. This indicated that H-Group had much greater systole–diastole material stiffness variations. At beginning-of-ejection (BE), LV ejection fraction (LVEF) showed positive correlation with C-curvature, stress, and strain, and negative correlation with LV volume, respectively. At beginning-of-filling (BF), LVEF showed positive correlation with C-curvature and strain, but negative correlation with stress and LV volume, respectively. Using averaged values of two groups at BE, I-Group stress, strain, and wall thickness were 32%, 29%, and 18% lower (thinner), respectively, compared to those of H-Group. L-curvature from I-Group was 61% higher than that from H-Group. Difference in C-curvature between the two groups was not statistically significant. Our results indicated that our modeling approach has the potential to determine in vivo ventricle material properties, which in turn could lead to methods to infer presence of infarct from LV contractibility and material stiffness variations. Quantitative differences in LV volume, curvatures, stress, strain, and wall thickness between the two groups were provided.

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Life Tables of Two-Spotted Spider Mite Tetranychus urticae Koch (Acari: Tetranychidae) and its Predator Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae)

Journal of Bio-Science ◽

10.3329/jbs.v16i0.3733 ◽

1970 ◽

Vol 16 ◽

pp. 1-10 ◽

Cited By ~ 5

Author(s):

M Fazlul Hoque ◽

W Islam ◽

M Khalequzzaman

Keyword(s):

Tetranychus Urticae ◽

Generation Time ◽

Development Time ◽

Phytoseiulus Persimilis ◽

Reproductive Rate ◽

Finite Capacity ◽

Net Reproductive Rate ◽

Wide Range ◽

The Mean ◽

Capacity For Increase

Life table of Tetranychus urticae and Phytoseiulus persimilis on bean leaflets were studied under laboratory conditions in three seasons. For T. urticae the development time from egg to adult varied from 7 to 24 days and the highest immature mortality was 78.70 % in winter. Eggs laid by females were 88.1 eggs in autumn and 70.6 eggs in summer season. The gross reproductive rate (GRR) was the highest (65.51) in autumn and 52.50 in summer. The net reproductive rate (Ro) was the highest (15.862) in autumn and 8.916 in summer. The intrinsic rates of increase (rm) and finite capacity for increase (λ) reached maximal values (0.1873 and 1.206) in autumn, whereas minimal values (0.056 and 1.058) were in winter season. The mean generation time (T) was the shortest in summer and double (3.701) days in autumn. The development time of P. persimilis from egg to adult varied from 5 to 14 days. The highest immature mortality was 60% in summer. Eggs laid by females were 39.4 eggs in autumn and 30.2 eggs in summer. The gross reproductive rate (GRR) was the highest (31.4) in autumn and 24.0 in summer. The net reproductive rate (Ro) was the highest (10.573) in autumn and 8.460 in winter. The intrinsic rates of increase (rm) and finite capacity for increase (λ) reached maximal values (0.1823 and 1.200) in summer, whereas minimal values (0.1025 and 1.108) were in winter. The mean generation time (T) was the shortest in summer. The results suggested that P. persimilis could develop and reproduce within a wide range of temperatures. Key words: Tetranychus urticae, Phytoseiulus persimilis, immature mortality, intrinsic rates of increase, reproductive rate, Survival DOI:10.3329/jbs.v16i0.3733 J. bio-sci. 16: 1-10, 2008

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Nuclear DNA content and minimum generation time in herbaceous plants

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1972.0042 ◽

1972 ◽

Vol 181 (1063) ◽

pp. 109-135 ◽

Cited By ~ 406

Keyword(s):

Cell Cycle ◽

Dna Content ◽

Cycle Time ◽

Generation Time ◽

Nuclear Dna ◽

Nuclear Dna Content ◽

Annual Species ◽

Cell Cycle Time ◽

Developmental Processes ◽

The Mean

Many components of cell and nuclear size and mass are correlated with nuclear DNA content in plants, as also are the durations and rates of such developmental processes as mitosis and meiosis. It is suggested that the multiple effects of the mass of nuclear DNA which affect all cells and apply throughout the life of the plant can together determine the minimum generation time for each species. The durations of mitosis and of meiosis are both positively correlated with nuclear DNA content and, therefore, species with a short minimum generation time might be expected to have a shorter mean cell cycle time and mean meiotic duration, and a lower mean nuclear DNA content, than species with a long mean minimum generation time. In tests of this hypothesis, using data collated from the literature, it is shown that the mean cell cycle time and the mean meiotic duration in annual species is significantly shorter than in perennial species. Furthermore, the mean nuclear DNA content of annual species is significantly lower than for perennial species both in dicotyledons and monocotyledons. Ephemeral species have a significantly lower mean nuclear DNA content than annual species. Among perennial monocotyledons the mean nuclear DNA content of species which can complete a life cycle within one year (facultative perennials) is significantly lower than the mean nuclear DNA content of those which cannot (obligate perennials). However, the mean nuclear DNA content of facultative perennials does not differ significantly from the mean for annual species. It is suggested that the effects of nuclear DNA content on the duration of developmental processes are most obvious during its determinant stages, and that the largest effects of nuclear DNA mass are expressed at times when development is slowest, for instance, during meiosis or at low temperature. It has been suggested that DNA influences development in two ways, directly through its informational content, and indirectly by the physical-mechanical effects of its mass. The term 'nucleotype' is used to describe those conditions of the nucleus which effect the phenotype independently of the informational content of the DNA. It is suggested that cell cycle time, meiotic duration, and minimum generation time are determined by the nucleotype. In addition, it may be that satellite DNA is significant in its nucleotypic effects on developmental processes.

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