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  1. Article ; Online: Refining Reproduction Number Estimates to Account for Unobserved Generations of Infection in Emerging Epidemics.

    Brizzi, Andrea / O'Driscoll, Megan / Dorigatti, Ilaria

    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America

    2022  Volume 75, Issue 1, Page(s) e114–e121

    Abstract: Background: Estimating the transmissibility of infectious diseases is key to inform situational awareness and for response planning. Several methods tend to overestimate the basic (R0) and effective (Rt) reproduction numbers during the initial phases of ...

    Abstract Background: Estimating the transmissibility of infectious diseases is key to inform situational awareness and for response planning. Several methods tend to overestimate the basic (R0) and effective (Rt) reproduction numbers during the initial phases of an epidemic. In this work we explore the impact of incomplete observations and underreporting of the first generations of infections during the initial epidemic phase.
    Methods: We propose a debiasing procedure that utilizes a linear exponential growth model to infer unobserved initial generations of infections and apply it to EpiEstim. We assess the performance of our adjustment using simulated data, considering different levels of transmissibility and reporting rates. We also apply the proposed correction to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) incidence data reported in Italy, Sweden, the United Kingdom, and the United States.
    Results: In all simulation scenarios, our adjustment outperforms the original EpiEstim method. The proposed correction reduces the systematic bias, and the quantification of uncertainty is more precise, as better coverage of the true R0 values is achieved with tighter credible intervals. When applied to real-world data, the proposed adjustment produces basic reproduction number estimates that closely match the estimates obtained in other studies while making use of a minimal amount of data.
    Conclusions: The proposed adjustment refines the reproduction number estimates obtained with the current EpiEstim implementation by producing improved, more precise estimates earlier than with the original method. This has relevant public health implications.
    MeSH term(s) Basic Reproduction Number ; COVID-19/epidemiology ; Epidemics ; Humans ; Reproduction ; SARS-CoV-2
    Language English
    Publishing date 2022-02-16
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1099781-7
    ISSN 1537-6591 ; 1058-4838
    ISSN (online) 1537-6591
    ISSN 1058-4838
    DOI 10.1093/cid/ciac138
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: SARIMA-modelled greater severity and mortality during the 2010/11 post-pandemic influenza season compared to the 2009 H1N1 pandemic in English hospitals.

    Lau, Krystal / Dorigatti, Ilaria / Miraldo, Marisa / Hauck, Katharina

    International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases

    2021  Volume 105, Page(s) 161–171

    Abstract: Objective: The COVID-19 pandemic demonstrates the need for understanding pathways to healthcare demand, morbidity, and mortality of pandemic patients. We estimate H1N1 (1) hospitalization rates, (2) severity rates (length of stay, ventilation, pneumonia, ...

    Abstract Objective: The COVID-19 pandemic demonstrates the need for understanding pathways to healthcare demand, morbidity, and mortality of pandemic patients. We estimate H1N1 (1) hospitalization rates, (2) severity rates (length of stay, ventilation, pneumonia, and death) of those hospitalized, (3) mortality rates, and (4) time lags between infections and hospitalizations during the pandemic (June 2009 to March 2010) and post-pandemic influenza season (November 2010 to February 2011) in England.
    Methods: Estimates of H1N1 infections from a dynamic transmission model are combined with hospitalizations and severity using time series econometric analyses of administrative patient-level hospital data.
    Results: Hospitalization rates were 34% higher and severity rates of those hospitalized were 20%-90% higher in the post-pandemic period than the pandemic. Adults (45-64-years-old) had the highest ventilation and pneumonia hospitalization rates. Hospitalizations did not lag infection during the pandemic for the young (<24-years-old) but lagged by one or more weeks for all ages in the post-pandemic period.
    Discussion: The post-pandemic flu season exhibited heightened H1N1 severity, long after the pandemic was declared over. Policymakers should remain vigilant even after pandemics seem to have subsided. Analysis of administrative hospital data and epidemiological modelling estimates can provide valuable insights to inform responses to COVID-19 and future influenza and other disease pandemics.
    MeSH term(s) Adolescent ; Adult ; Aged ; Aged, 80 and over ; Child ; Child, Preschool ; England/epidemiology ; Female ; Hospitalization/statistics & numerical data ; Humans ; Influenza A Virus, H1N1 Subtype ; Influenza, Human/epidemiology ; Influenza, Human/mortality ; Male ; Middle Aged ; Pandemics ; Severity of Illness Index ; Time Factors ; Young Adult
    Language English
    Publishing date 2021-02-03
    Publishing country Canada
    Document type Comparative Study ; Journal Article
    ZDB-ID 1331197-9
    ISSN 1878-3511 ; 1201-9712
    ISSN (online) 1878-3511
    ISSN 1201-9712
    DOI 10.1016/j.ijid.2021.01.070
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  3. Article ; Online: Quantifying the risk of Zika virus spread in Asia during the 2015-16 epidemic in Latin America and the Caribbean: A modeling study.

    Luo, Xue Shi / Imai, Natsuko / Dorigatti, Ilaria

    Travel medicine and infectious disease

    2020  Volume 33, Page(s) 101562

    Abstract: Background: No large-scale Zika epidemic has been observed to date in Southeast Asia following the 2015-16 Latin American and the Caribbean epidemic. One hypothesis is Southeast Asian populations' partial immunity to Zika.: Method: We estimated the ... ...

    Abstract Background: No large-scale Zika epidemic has been observed to date in Southeast Asia following the 2015-16 Latin American and the Caribbean epidemic. One hypothesis is Southeast Asian populations' partial immunity to Zika.
    Method: We estimated the two conditions for a Zika outbreak emergence in Southeast Asia: (i) the risk of Zika introduction from Latin America and the Caribbean and, (ii) the risk of autochthonous transmission under varying assumptions on population immunity. We also validated the model used to estimate the risk of introduction by comparing the estimated number of Zika seeds introduced into the United States with case counts reported by the Centers for Disease Control and Prevention (CDC).
    Results: There was good agreement between our estimates and case counts reported by the CDC. We thus applied the model to Southeast Asia and estimated that, on average, 1-10 seeds were introduced into Indonesia, Malaysia, the Philippines, Singapore, Thailand and Vietnam. We also found increasing population immunity levels from 0 to 90% reduced probability of autochthonous transmission by 40% and increasing individual variation in transmission further reduced the outbreak probability.
    Conclusions: Population immunity, combined with heterogeneity in transmission, can explain why no large-scale outbreak was observed in Southeast Asia during the 2015-16 epidemic.
    MeSH term(s) Asia/epidemiology ; Caribbean Region/epidemiology ; Humans ; Latin America/epidemiology ; Risk Assessment/methods ; Risk Assessment/standards ; Risk Factors ; Zika Virus ; Zika Virus Infection/epidemiology
    Language English
    Publishing date 2020-01-26
    Publishing country Netherlands
    Document type Journal Article ; Validation Study
    ZDB-ID 2170891-5
    ISSN 1873-0442 ; 1477-8939
    ISSN (online) 1873-0442
    ISSN 1477-8939
    DOI 10.1016/j.tmaid.2020.101562
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Comparison of machine learning methods for estimating case fatality ratios: An Ebola outbreak simulation study.

    Forna, Alpha / Dorigatti, Ilaria / Nouvellet, Pierre / Donnelly, Christl A

    PloS one

    2021  Volume 16, Issue 9, Page(s) e0257005

    Abstract: Background: Machine learning (ML) algorithms are now increasingly used in infectious disease epidemiology. Epidemiologists should understand how ML algorithms behave within the context of outbreak data where missingness of data is almost ubiquitous.: ... ...

    Abstract Background: Machine learning (ML) algorithms are now increasingly used in infectious disease epidemiology. Epidemiologists should understand how ML algorithms behave within the context of outbreak data where missingness of data is almost ubiquitous.
    Methods: Using simulated data, we use a ML algorithmic framework to evaluate data imputation performance and the resulting case fatality ratio (CFR) estimates, focusing on the scale and type of data missingness (i.e., missing completely at random-MCAR, missing at random-MAR, or missing not at random-MNAR).
    Results: Across ML methods, dataset sizes and proportions of training data used, the area under the receiver operating characteristic curve decreased by 7% (median, range: 1%-16%) when missingness was increased from 10% to 40%. Overall reduction in CFR bias for MAR across methods, proportion of missingness, outbreak size and proportion of training data was 0.5% (median, range: 0%-11%).
    Conclusion: ML methods could reduce bias and increase the precision in CFR estimates at low levels of missingness. However, no method is robust to high percentages of missingness. Thus, a datacentric approach is recommended in outbreak settings-patient survival outcome data should be prioritised for collection and random-sample follow-ups should be implemented to ascertain missing outcomes.
    MeSH term(s) Computer Simulation ; Data Interpretation, Statistical ; Datasets as Topic ; Disease Outbreaks ; Hemorrhagic Fever, Ebola/epidemiology ; Hemorrhagic Fever, Ebola/mortality ; Humans ; Machine Learning ; Models, Statistical ; Research Design ; Survival Analysis
    Language English
    Publishing date 2021-09-15
    Publishing country United States
    Document type Comparative Study ; Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2267670-3
    ISSN 1932-6203 ; 1932-6203
    ISSN (online) 1932-6203
    ISSN 1932-6203
    DOI 10.1371/journal.pone.0257005
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Yellow fever in Asia-a risk analysis.

    Cracknell Daniels, Bethan / Gaythorpe, Katy / Imai, Natsuko / Dorigatti, Ilaria

    Journal of travel medicine

    2021  Volume 28, Issue 3

    Abstract: Background: There is concern about the risk of yellow fever (YF) establishment in Asia, owing to rising numbers of urban outbreaks in endemic countries and globalisation. Following an outbreak in Angola in 2016, YF cases were introduced into China. ... ...

    Abstract Background: There is concern about the risk of yellow fever (YF) establishment in Asia, owing to rising numbers of urban outbreaks in endemic countries and globalisation. Following an outbreak in Angola in 2016, YF cases were introduced into China. Prior to this, YF had never been recorded in Asia, despite climatic suitability and the presence of mosquitoes. An outbreak in Asia could result in widespread fatalities and huge economic impact. Therefore, quantifying the potential risk of YF outbreaks in Asia is a public health priority.
    Methods: Using international flight data and YF incidence estimates from 2016, we quantified the risk of YF introduction via air travel into Asia. In locations with evidence of a competent mosquito population, the potential for autochthonous YF transmission was estimated using a temperature-dependent model of the reproduction number and a branching process model assuming a negative binomial distribution.
    Results: In total, 25 cities across Asia were estimated to be at risk of receiving at least one YF viraemic traveller during 2016. At their average temperatures, we estimated the probability of autochthonous transmission to be <50% in all cities, which was primarily due to the limited number of estimated introductions that year.
    Conclusion: Despite the rise in air travel, we found low support for travel patterns between YF endemic countries and Asia resulting in autochthonous transmission during 2016. This supports the historic absence of YF in Asia and suggests it could be due to a limited number of introductions in previous years. Future increases in travel volumes or YF incidence can increase the number of introductions and the risk of autochthonous transmission. Given the high proportion of asymptomatic or mild infections and the challenges of YF surveillance, our model can be used to estimate the introduction and outbreak risk and can provide useful information to surveillance systems.
    MeSH term(s) Aedes ; Angola/epidemiology ; Animals ; Asia ; Cities ; Disease Outbreaks/prevention & control ; Female ; Humans ; Risk Assessment ; Travel-Related Illness ; Yellow Fever/epidemiology ; Yellow Fever/prevention & control ; Yellow Fever/transmission ; Yellow fever virus/physiology
    Language English
    Publishing date 2021-01-28
    Publishing country England
    Document type Journal Article
    ZDB-ID 1212504-0
    ISSN 1708-8305 ; 1195-1982
    ISSN (online) 1708-8305
    ISSN 1195-1982
    DOI 10.1093/jtm/taab015
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  6. Article ; Online: Impact of early phase COVID-19 precautionary behaviors on seasonal influenza in Hong Kong: A time-series modeling approach.

    Lin, Chun-Pang / Dorigatti, Ilaria / Tsui, Kwok-Leung / Xie, Min / Ling, Man-Ho / Yuan, Hsiang-Yu

    Frontiers in public health

    2022  Volume 10, Page(s) 992697

    Abstract: Background: Before major non-pharmaceutical interventions were implemented, seasonal incidence of influenza in Hong Kong showed a rapid and unexpected reduction immediately following the early spread of COVID-19 in mainland China in January 2020. This ... ...

    Abstract Background: Before major non-pharmaceutical interventions were implemented, seasonal incidence of influenza in Hong Kong showed a rapid and unexpected reduction immediately following the early spread of COVID-19 in mainland China in January 2020. This decline was presumably associated with precautionary behavioral changes (e.g., wearing face masks and avoiding crowded places). Knowing their effectiveness on the transmissibility of seasonal influenza can inform future influenza prevention strategies.
    Methods: We estimated the effective reproduction number (
    Findings: The model-estimated mean
    Conclusion: Our model results indicate that wearing face masks and avoiding crowded places could have potentially significant suppressive impacts on influenza.
    MeSH term(s) Humans ; Influenza, Human/epidemiology ; Influenza, Human/prevention & control ; COVID-19/epidemiology ; COVID-19/prevention & control ; Bayes Theorem ; Time Factors ; Masks
    Language English
    Publishing date 2022-11-14
    Publishing country Switzerland
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2711781-9
    ISSN 2296-2565 ; 2296-2565
    ISSN (online) 2296-2565
    ISSN 2296-2565
    DOI 10.3389/fpubh.2022.992697
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  7. Article ; Online: Modelling the viral dynamics of the SARS-CoV-2 Delta and Omicron variants in different cell types.

    McCormack, Clare P / Yan, Ada W C / Brown, Jonathan C / Sukhova, Ksenia / Peacock, Thomas P / Barclay, Wendy S / Dorigatti, Ilaria

    Journal of the Royal Society, Interface

    2023  Volume 20, Issue 205, Page(s) 20230187

    Abstract: We use viral kinetic models fitted to viral load data ... ...

    Abstract We use viral kinetic models fitted to viral load data from
    MeSH term(s) Humans ; COVID-19 ; SARS-CoV-2 ; Basic Reproduction Number ; Kinetics
    Language English
    Publishing date 2023-08-09
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2156283-0
    ISSN 1742-5662 ; 1742-5689
    ISSN (online) 1742-5662
    ISSN 1742-5689
    DOI 10.1098/rsif.2023.0187
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  8. Article ; Online: Refining reproduction number estimates to account for unobserved generations of infection in emerging epidemics

    Brizzi, Andrea / O'Driscoll, Megan / Dorigatti, Ilaria

    medRxiv

    Abstract: Background Estimating the transmissibility of infectious diseases is key to inform situational awareness and for response planning. Several methods tend to overestimate the basic (R_0) and effective (R_t) reproduction numbers during the initial phases of ...

    Abstract Background Estimating the transmissibility of infectious diseases is key to inform situational awareness and for response planning. Several methods tend to overestimate the basic (R_0) and effective (R_t) reproduction numbers during the initial phases of an epidemic. The reasons driving the observed bias are unknown. In this work we explore the impact of incomplete observations and underreporting of the first generations of infections during the initial epidemic phase. Methods We propose a debiasing procedure which utilises a linear exponential growth model to infer unobserved initial generations of infections and apply it to EpiEstim. We assess the performance of our adjustment using simulated data, considering different levels of transmissibility and reporting rates. We also apply the proposed correction to reported SARS-CoV-2 incidence data reported in Italy, Sweden, the United Kingdom and the United States of America. Results In all simulation scenarios, our adjustment outperforms the original EpiEstim method. The proposed correction reduces the systematic bias and the quantification of uncertainty is more precise, as better coverage of the true R_0 values is achieved with tighter credible intervals. When applied to real world data, the proposed adjustment produces basic reproduction number estimates which closely match the estimates obtained in other studies while making use of a minimal amount of data. Conclusions The proposed adjustment refines the reproduction number estimates obtained with the current EpiEstim implementation by producing improved, more precise estimates earlier than with the original method. This has relevant public health implications.
    Keywords covid19
    Language English
    Publishing date 2021-11-09
    Publisher Cold Spring Harbor Laboratory Press
    Document type Article ; Online
    DOI 10.1101/2021.11.08.21266033
    Database COVID19

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  9. Article ; Online: Spatiotemporal variability in case fatality ratios for the 2013-2016 Ebola epidemic in West Africa.

    Forna, Alpha / Dorigatti, Ilaria / Nouvellet, Pierre / Donnelly, Christl A

    International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases

    2020  Volume 93, Page(s) 48–55

    Abstract: Background: For the 2013-2016 Ebola epidemic in West Africa, the largest Ebola virus disease (EVD) epidemic to date, we aim to analyse the patient mix in detail to characterise key sources of spatiotemporal heterogeneity in the case fatality ratios (CFR) ...

    Abstract Background: For the 2013-2016 Ebola epidemic in West Africa, the largest Ebola virus disease (EVD) epidemic to date, we aim to analyse the patient mix in detail to characterise key sources of spatiotemporal heterogeneity in the case fatality ratios (CFR).
    Methods: We applied a non-parametric Boosted Regression Trees (BRT) imputation approach for patients with missing survival outcomes and adjusted for model imperfection. Semivariogram analysis and kriging were used to investigate spatiotemporal heterogeneities.
    Results: CFR estimates varied significantly between districts and over time over the course of the epidemic. BRT modelling accounted for most of the spatiotemporal variation and interactions in CFR, but moderate spatial autocorrelation remained for distances up to approximately 90 km. Combining district-level CFR estimates and kriged district-level residuals provided the best linear unbiased predicted map of CFR accounting for the both explained and unexplained spatial variation. Temporal autocorrelation was not observed in the district-level residuals from the BRT estimates.
    Conclusions: This study provides new insight into the epidemiology of the 2013-2016 West African Ebola epidemic with a view of informing future public health contingency planning, resource allocation and impact assessment. The analytical framework developed in this analysis, coupled with key domain knowledge, could be deployed in real time to support the response to ongoing and future outbreaks.
    MeSH term(s) Africa, Western/epidemiology ; Epidemics ; Hemorrhagic Fever, Ebola/epidemiology ; Hemorrhagic Fever, Ebola/mortality ; Humans ; Spatial Analysis
    Language English
    Publishing date 2020-01-28
    Publishing country Canada
    Document type Journal Article
    ZDB-ID 1331197-9
    ISSN 1878-3511 ; 1201-9712
    ISSN (online) 1878-3511
    ISSN 1201-9712
    DOI 10.1016/j.ijid.2020.01.046
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  10. Article ; Online: Estimating dengue transmission intensity from serological data: A comparative analysis using mixture and catalytic models.

    Cox, Victoria / O'Driscoll, Megan / Imai, Natsuko / Prayitno, Ari / Hadinegoro, Sri Rezeki / Taurel, Anne-Frieda / Coudeville, Laurent / Dorigatti, Ilaria

    PLoS neglected tropical diseases

    2022  Volume 16, Issue 7, Page(s) e0010592

    Abstract: Background: Dengue virus (DENV) infection is a global health concern of increasing magnitude. To target intervention strategies, accurate estimates of the force of infection (FOI) are necessary. Catalytic models have been widely used to estimate DENV ... ...

    Abstract Background: Dengue virus (DENV) infection is a global health concern of increasing magnitude. To target intervention strategies, accurate estimates of the force of infection (FOI) are necessary. Catalytic models have been widely used to estimate DENV FOI and rely on a binary classification of serostatus as seropositive or seronegative, according to pre-defined antibody thresholds. Previous work has demonstrated the use of thresholds can cause serostatus misclassification and biased estimates. In contrast, mixture models do not rely on thresholds and use the full distribution of antibody titres. To date, there has been limited application of mixture models to estimate DENV FOI.
    Methods: We compare the application of mixture models and time-constant and time-varying catalytic models to simulated data and to serological data collected in Vietnam from 2004 to 2009 (N ≥ 2178) and Indonesia in 2014 (N = 3194).
    Results: The simulation study showed larger mean FOI estimate bias from the time-constant and time-varying catalytic models (-0.007 (95% Confidence Interval (CI): -0.069, 0.029) and -0.006 (95% CI -0.095, 0.043)) than from the mixture model (0.001 (95% CI -0.036, 0.065)). Coverage of the true FOI was > 95% for estimates from both the time-varying catalytic and mixture model, however the latter had reduced uncertainty. When applied to real data from Vietnam, the mixture model frequently produced higher FOI and seroprevalence estimates than the catalytic models.
    Conclusions: Our results suggest mixture models represent valid, potentially less biased, alternatives to catalytic models, which could be particularly useful when estimating FOI from data with largely overlapping antibody titre distributions.
    MeSH term(s) Dengue ; Humans ; Indonesia/epidemiology ; Seroepidemiologic Studies ; Vietnam/epidemiology
    Language English
    Publishing date 2022-07-11
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2429704-5
    ISSN 1935-2735 ; 1935-2735
    ISSN (online) 1935-2735
    ISSN 1935-2735
    DOI 10.1371/journal.pntd.0010592
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