scholarly journals Examining the incubation period distributions of COVID-19 on Chinese patients with different travel histories

2020 ◽  
Vol 14 (04) ◽  
pp. 323-327 ◽  
Author(s):  
Zuopeng Xiao ◽  
Xi Xie ◽  
Wenbo Guo ◽  
Zhiqiang Luo ◽  
Jianxiang Liao ◽  
...  
Keyword(s):  
Incubation Period ◽  
Local Community ◽  
Case Reports ◽  
Epidemiological Survey ◽  
Chinese Patients ◽  
Posterior Median ◽  
Period Distribution ◽  
Incubation Periods ◽  
Community Transmission ◽  
Patient Groups

Introduction: Current studies estimated a general incubation period distribution of COVID-19 based on early-confirmed cases in Wuhan, and have not examined whether the incubation period distribution varies across population segments with different travel histories. We aimed to examine whether patients infected by community transmission had extended incubation periods than the early generation patients who had direct exposures to Wuhan. Methodology: Based on 4741 patient case reports from municipal centers of disease control by February 21, 2020, we calculated the incubation periods of 2555 patients with clear epidemiological survey information and illness development timeline. All patients were categorized into five groups by their travel histories. Incubation period distributions were modeled for each group by the method of the posterior Weibull distribution estimation. Results: Adults aged 30 to 59 years had the most substantial proportion of confirmed cases in China. The incubation period distribution varied slightly across patient groups with different travel histories. Patients who regularly lived in Wuhan and left to other locations before January 23, 2020 had the shortest posterior median value of 7.57 days for the incubation period, while the incubation periods for persons affected by local community transmission had the largest posterior median of incubation periods, 9.31 days. Conclusions: The median incubation period for all patients infected outside Wuhan was 9 days, a bit of more extended than the early estimated 5-day incubation period that was based on patients in Wuhan. Our findings may imply the decreases of virulence of the COVID-19 virus along with intergenerational transmission.

scholarly journals Examining geographical disparities in the incubation period of the COVID-19 infected cases in Shenzhen and Hefei, China

2020 ◽  
Author(s):  
Xiao Zuopeng ◽  
Wenbo Guo ◽  
Luo Zhiqiang ◽  
Liao Jianxiang ◽  
Wen Feiqiu ◽  
...  
Keyword(s):  
Incubation Period ◽  
Epidemiological Survey ◽  
Clinical Report ◽  
Econometric Methods ◽  
Period Distribution ◽  
Environmental Attributes ◽  
Viral Virulence ◽  
Incubation Periods ◽  
Report Data ◽  
Geographical Locations

Abstract Aim Current studies on the COVID-19 depicted a general incubation period distribution and did not examine whether the incubation period distribution varies across patients living in different geographical locations with varying environmental attributes. Profiling the incubation distributions geographically help to determine the appropriate quarantine duration for different regions.Subject and Methods This retrospective study mainly used publicly-accessible clinical report data for patients (n=543) confirmed as infected in Shenzhen and Heifei, China. Based on 217 patients on whom the incubation period could be identified by the epidemiological survey. Statistical and econometric methods were used to investigate how the incubation distributions varied between infected cases reported in Shenzhen and Hefei. Results The median of incubation periods of the COVID-19 for all 217 infected patients was 8 days (95% CI 7 to 9), while median values were 9 days in Shenzhen and 4 days in Heifei. The incubation period probably has an inverse U-shaped association with the meteorological temperature. The warmer condition in the winter of Shenzhen, average environmental temperature between 10℃ to 15℃, may decrease viral virulence and result in more extended incubation periods.Conclusion Case studies of the COVID-19 outbreak in Shenzhen and Hefei indicated that the incubation period of COVID-19 had exhibited evident geographical disparities, although the pathological causality between meteorological conditions and incubation period deserves further investigation.

scholarly journals The incubation period of COVID-19: A scoping review and meta-analysis to aid modelling and planning

2020 ◽  
Author(s):  
Prakashini Banka ◽  
Catherine Comiskey
Keyword(s):  
Incubation Period ◽  
Scoping Review ◽  
Meta Analysis ◽  
Accurate Estimate ◽  
Mitigation Strategies ◽  
Global Index ◽  
Distribution Modelling ◽  
Period Distribution ◽  
Incubation Periods ◽  
The Mean

AbstractBackgroundAn accurate estimate of the distribution of the incubation period for COVID-19 is the foundational building block for modelling the spread of the SARS COV2 and the effectiveness of mitigation strategies on affected communities. Initial estimates were based on early infections, the aim of this study was to provide an updated estimate and meta-analysis of the incubation period distribution for COVID-19.MethodsThe review was conducted according to the PRISMA Scoping Review guidelines. Five databases were searched; CINAHL, MEDLINE, PUBMED, EMBASE, ASSIA, and Global Index Medicus for studies published between 1 January 2020 - 27 July 2020.ResultsA total of 1,084 articles were identified through the database searches and 1 article was identified through the reference screening of retrieved articles. After screening 64 articles were included. The studies combined had a sample of 45,151 people. The mean of the incubation periods was 6.71 days with 95% CIs ranging from 1 to 12.4 days. The median was 6 days and IQR ranging from 1.8 to 16.3. The resulting parameters for a Gamma Distribution modelling the incubation period were Γ(α, λ) = Γ(2.810,0.419) with mean, μ = α/λ.ConclusionGovernments are planning their strategies on a maximum incubation period of 14 days. While our results are limited to primarily Chinese research studies, the findings highlight the variability in the mean period and the potential for further incubation beyond 14 days. There is an ongoing need for detailed surveillance on the timing of self-isolation periods and related measures protecting communities as incubation periods may be longer.

scholarly journals The incubation period of COVID-19 – A rapid systematic review and meta-analysis of observational research

2020 ◽  
Author(s):  
Conor G. McAloon ◽  
Áine B. Collins ◽  
Kevin Hunt ◽  
Ann Barber ◽  
Andrew W. Byrne ◽  
...  
Keyword(s):  
Systematic Review ◽  
Decision Making ◽  
Incubation Period ◽  
Lognormal Distribution ◽  
Meta Analysis ◽  
Observational Research ◽  
List Type ◽  
Period Distribution ◽  
Incubation Periods ◽  
Inform Decision Making

ABSTRACTBackgroundReliable estimates of the incubation period are important for decision making around the control of infectious diseases. Knowledge of the incubation period distribution can be used directly to inform decision-making or as inputs into mathematical models.ObjectivesThe aim of this study was to conduct a rapid systematic review and meta-analysis of estimates of the incubation periods of COVID-19.DesignRapid systematic review and meta-analysis of observational researchData sourcesPublications on the electronic databases PubMed, Google Scholar, MedRxiv and BioRxiv were searched. The search was not limited to peer-reviewed published data, but also included pre-print articles.Study appraisal and synthesis methodsStudies were selected for meta-analysis if they reported either the parameters and confidence intervals of the distributions fit to the data, or sufficient information to facilitate calculation of those values. The majority of studies suitable for inclusion in the final analysis modelled incubation period as a lognormal distribution. We conducted a random effects meta-analysis of the parameters of this distribution.ResultsThe incubation period distribution may be modelled with a lognormal distribution with pooled mu and sigma parameters of 1.63 (1.51, 1.75) and 0.50 (0.45, 0.55) respectively. The corresponding mean was 5.8 (5.01, 6.69 days). It should be noted that uncertainty increases towards the tail of the distribution: the pooled parameter estimates resulted in a median incubation period of 5.1 (4.5, 5.8) days, whereas the 95th percentile was 11.6 (9.5, 14.2) days.Conclusions and implicationsThe choice of which parameter values are adopted will depend on how the information is used, the associated risks and the perceived consequences of decisions to be taken. These recommendations will need to be revisited once further relevant information becomes available. Finally, we present an RShiny app that facilitates updating these estimates as new data become available.ARTICLE SUMMARYStrengths and limitations of this studyThis study provides a pooled estimate of the distribution of incubation periods which may be used in subsequent modelling studies or to inform decision-makingThis estimate will need to be revisited as subsequent data become available. We present an RShiny app to allow the meta-analysis to be updated with new estimates

Natural maize phytochemicals for control of maize mycoflora and aflatoxigenic fungi

2009 ◽  
Vol 2 (3) ◽  
pp. 305-312 ◽  
Author(s):  
A. Nesci ◽  
S. Marín ◽  
M. Etcheverry ◽  
V. Sanchis
Keyword(s):  
Ferulic Acid ◽  
Incubation Period ◽  
Cinnamic Acid ◽  
Inhibitory Effect ◽  
Aspergillus Section Flavi ◽  
Aflatoxigenic Fungi ◽  
Incubation Periods ◽  
Maize Grain ◽  
Aflatoxin B ◽  
Aspergillus Section

This research was undertaken to evaluate the effects of the natural phytochemicals trans-cinnamic acid (CA) alone at concentrations of 20 and 25 mM, ferulic acid (FA) at concentration of 30 mM and two mixtures, CA-FA (20+30 mM) and CA-FA (25+30 mM) on natural maize mycoflora, Aspergillus section Flavi population and aflatoxin B1 production. These studies were carried out in maize grain in relation to a water activity of 0.99, 0.97 and 0.94. CA at 25 mM and the mixture CA-FA (25+30 mM) were the most effective treatments at inhibiting natural maize mycoflora at all aw assayed after 11 and 35 days of incubation at 25 °C. In general, 20 mM CA caused complete inhibition of Aspergillus section Flavi population at all aw values tested during all incubation period without an additional inoculum. 20 mM CA and 25 mM CA showed the major inhibitory effect on aflatoxin B1 accumulation of control and Aspergillus section Flavi additionally inoculated during all incubation periods. The data showed that CA and FA could be considered as effective fungitoxicants for natural maize mycoflora and aflatoxigenic fungi in the aw range 0.99 to 0.94. The information obtained shows promise for controlling aflatoxigenic fungi in stored maize.

scholarly journals Effect of Sucrose Concentrations and Incubation Periods on in Vitro Rooting of Moris Pineapple (Ananas comosus)

2019 ◽  
Vol 34 (4) ◽  
pp. 230-242
Author(s):  
Abdelhamid M Hamad
Keyword(s):  
Incubation Period ◽  
In Vitro Rooting ◽  
Ananas Comosus ◽  
Ms Medium ◽  
Incubation Periods ◽  
Half Strength

The effect of 6 sucrose concentrations (5, 10, 15, 20, 25, 30 g/l) over 4 incubation periods (30, 45, 60, 75 days) on in vitro rooting of Moris pineapple cultured in liquid half strength MS medium enriched with IBA at 2.0 mg/l was investigated. At all incubation periods, all shoots in medium enriched with sucrose at 5 g/l failed to root, and no roots formed within the first 30 days in medium enriched with sucrose at 10 g/l. After 30 days of incubation, the highest rooting percentage (66 %), tallest plantlets (23 mm tall), highest (3.4 roots) and longest (5.3 mm) root per shoot were obtained in medium enriched with sucrose at 25, 10, 15, 15 g/l respectively, while after 45 days, the highest of all rooting aspects (75 %, 32.3 mm tall, 3.7 roots, 7 mm long), were obtained in medium enriched with sucrose at 15 g/l. After 60 days, the highest rooting percentage (91.7 %) and tallest plantlets (36.7 mm tall) were obtained in medium enriched with sucrose at 20 g/l while highest roots per shoot (3.7 roots) and longest root (10.7 mm) were obtained in medium enriched with sucrose at 15 g/l. After 75 days, all shoots rooted (100 %) in medium enriched with sucrose at 10 and 20 g/l, while sucrose at 25 g/l resulted in tallest plantlets (46.3 mm tall) and at 20 g/l resulted in highest (4.7 roots) and longest roots (27.3 mm). At each incubation period, there was a different optimum sucrose enrichment for different rooting parameters.

scholarly journals Estimation of incubation period and serial interval of COVID-19: analysis of 178 cases and 131 transmission chains in Hubei province, China

2020 ◽  
Vol 148 ◽  
Author(s):  
Lin Yang ◽  
Jingyi Dai ◽  
Jun Zhao ◽  
Yunfu Wang ◽  
Pingji Deng ◽  
...  
Keyword(s):  
Incubation Period ◽  
Failure Time ◽  
Age Groups ◽  
Hubei Province ◽  
Interval Censoring ◽  
Contact Tracing ◽  
Considerable Proportion ◽  
Outbreak Period ◽  
Serial Interval ◽  
Incubation Periods

Abstract A novel coronavirus disease, designated as COVID-19, has become a pandemic worldwide. This study aims to estimate the incubation period and serial interval of COVID-19. We collected contact tracing data in a municipality in Hubei province during a full outbreak period. The date of infection and infector–infectee pairs were inferred from the history of travel in Wuhan or exposed to confirmed cases. The incubation periods and serial intervals were estimated using parametric accelerated failure time models, accounting for interval censoring of the exposures. Our estimated median incubation period of COVID-19 is 5.4 days (bootstrapped 95% confidence interval (CI) 4.8–6.0), and the 2.5th and 97.5th percentiles are 1 and 15 days, respectively; while the estimated serial interval of COVID-19 falls within the range of −4 to 13 days with 95% confidence and has a median of 4.6 days (95% CI 3.7–5.5). Ninety-five per cent of symptomatic cases showed symptoms by 13.7 days (95% CI 12.5–14.9). The incubation periods and serial intervals were not significantly different between male and female, and among age groups. Our results suggest a considerable proportion of secondary transmission occurred prior to symptom onset. And the current practice of 14-day quarantine period in many regions is reasonable.

scholarly journals Incubation periods of enteric illnesses in foodborne outbreaks, United States, 1998–2013

2019 ◽  
Vol 147 ◽  
Author(s):  
S. J. Chai ◽  
W. Gu ◽  
K. A. O'Connor ◽  
L. C. Richardson ◽  
R. V. Tauxe
Keyword(s):  
United States ◽  
Incubation Period ◽  
Disease Outbreaks ◽  
Disease Outbreak ◽  
Outbreak Investigation ◽  
Foodborne Disease ◽  
Case Definitions ◽  
Viral Pathogens ◽  
Incubation Periods ◽  
Foodborne Outbreaks

Abstract Early in a foodborne disease outbreak investigation, illness incubation periods can help focus case interviews, case definitions, clinical and environmental evaluations and predict an aetiology. Data describing incubation periods are limited. We examined foodborne disease outbreaks from laboratory-confirmed, single aetiology, enteric bacterial and viral pathogens reported to United States foodborne disease outbreak surveillance from 1998–2013. We grouped pathogens by clinical presentation and analysed the reported median incubation period among all illnesses from the implicated pathogen for each outbreak as the outbreak incubation period. Outbreaks from preformed bacterial toxins (Staphylococcus aureus, Bacillus cereus and Clostridium perfringens) had the shortest outbreak incubation periods (4–10 h medians), distinct from that of Vibrio parahaemolyticus (17 h median). Norovirus, salmonella and shigella had longer but similar outbreak incubation periods (32–45 h medians); campylobacter and Shiga toxin-producing Escherichia coli had the longest among bacteria (62–87 h medians); hepatitis A had the longest overall (672 h median). Our results can help guide diagnostic and investigative strategies early in an outbreak investigation to suggest or rule out specific etiologies or, when the pathogen is known, the likely timeframe for exposure. They also point to possible differences in pathogenesis among pathogens causing broadly similar syndromes.

scholarly journals Egg Size, Eggshell Porosity, and Incubation Period in the Marine Bird Family Alcidae

The Auk ◽  
2007 ◽  
Vol 124 (1) ◽  
pp. 307-315
Author(s):  
Karen Zimmermann ◽  
J. Mark Hipfner
Keyword(s):  
Incubation Period ◽  
Egg Size ◽  
Interspecific Variation ◽  
Egg Mass ◽  
Proximate Mechanisms ◽  
Diffusion Limited ◽  
Evolutionary Changes ◽  
Incubation Periods ◽  
Avian Incubation ◽  
Embryonic Metabolism

Abstract Although the ultimate factors that influence the duration of avian incubation periods are well known, we know much less about the proximate mechanisms by which birds adjust incubation period in response to selection. We tested the hypothesis that an adjustment in eggshell porosity is one such proximate mechanism (i.e., that avian species with higher ratios of incubation period to egg size lay eggs with less porous shells). Eggshell porosity affects the rate of gaseous exchange between the developing embryo and the external environment; thus, to the extent that embryonic metabolism is diffusion-limited, eggshell porosity could directly determine incubation period. To test that hypothesis, we collected eggs from seven species of Alcidae, a family of marine birds that exhibits an unusual degree of interspecific variation in incubation period, and measured egg mass and eggshell porosity (determined by the number and size of pores and the thickness of the shell). Incubation periods were obtained from the literature. Egg mass and eggshell porosity combined explained 87% of the variation in incubation period among the seven species, which included at least one member of each of the six main alcid lineages. As predicted, eggshell porosity and incubation period were negatively related, after controlling for egg mass. Our results are consistent with the hypothesis that evolutionary changes in avian incubation period may be attributed, at least in part, to adjustments in eggshell porosity. Taille de l’Œuf, Porosité de la Coquille et Période d’Incubation chez les Oiseaux Marins de la Famille des Alcidés

scholarly journals Incubation period for outbreak-associated, non-typhoidal salmonellosis cases, Minnesota, 2000–2015

2018 ◽  
Vol 146 (4) ◽  
pp. 423-429 ◽  
Author(s):  
D. Eikmeier ◽  
C. Medus ◽  
K. Smith
Keyword(s):  
Incubation Period ◽  
Period Length ◽  
Accurate Description ◽  
Vehicle Type ◽  
Day Range ◽  
Incubation Periods

AbstractIncubation period for non-typhoidal Salmonella (NTS) infections is generally reported as 6–72 h despite numerous reports of foodborne NTS outbreaks with median incubation periods >3 days. We summarised 16 years of Minnesota foodborne NTS outbreaks to better estimate the expected range of incubation periods for NTS infections. Of the 1517 NTS outbreak cases, 725 had enough data to calculate a precise incubation period. The median incubation period was 45 h; 77 (11%) cases had incubations ⩽12 h and 211 (29%) cases had incubations >72 h. Incubation period length varied by outbreak vehicle type, Salmonella serotype and outbreak setting. Based on our data, a more accurate description would be that the incubation of NTS infection is usually from 12 to 96 h, that incubations in >96 to 144 h (>4 to 6-day) range are not unusual and that incubations from 7 to 9 days and occasionally longer also occur.

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.

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