246 research outputs found
Impact of early-stage HIV transmission on treatment as prevention
Timely HIV treatment improves health (1)
and reduces transmission (2). These individual-
level benefits of HIV treatment for both
clinical and preventive purposes are well
established, but several questions remain
about the population-level impact of HIV
treatment as prevention (3). In PNAS, Eaton
and Hallett (4) use a mathematical model to
address one such question: Does the proportion
of transmission during early HIV infection
affect the impact of HIV treatment on
HIV incidence
Analysis of timeliness of infectious disease reporting in the Netherlands
<p>Abstract</p> <p>Background</p> <p>Timely reporting of infectious disease cases to public health authorities is essential to effective public health response. To evaluate the timeliness of reporting to the Dutch Municipal Health Services (MHS), we used as quantitative measures the intervals between onset of symptoms and MHS notification, and between laboratory diagnosis and notification with regard to six notifiable diseases.</p> <p>Methods</p> <p>We retrieved reporting data from June 2003 to December 2008 from the Dutch national notification system for shigellosis, EHEC/STEC infection, typhoid fever, measles, meningococcal disease, and hepatitis A virus (HAV) infection. For each disease, median intervals between date of onset and MHS notification were calculated and compared with the median incubation period. The median interval between date of laboratory diagnosis and MHS notification was similarly analysed. For the year 2008, we also investigated whether timeliness is improved by MHS agreements with physicians and laboratories that allow direct laboratory reporting. Finally, we investigated whether reports made by post, fax, or e-mail were more timely.</p> <p>Results</p> <p>The percentage of infectious diseases reported within one incubation period varied widely, between 0.4% for shigellosis and 90.3% for HAV infection. Not reported within two incubation periods were 97.1% of shigellosis cases, 76.2% of cases of EHEC/STEC infection, 13.3% of meningococcosis cases, 15.7% of measles cases, and 29.7% of typhoid fever cases. A substantial percentage of infectious disease cases was reported more than three days after laboratory diagnosis, varying between 12% for meningococcosis and 42% for shigellosis. MHS which had agreements with physicians and laboratories showed a significantly shorter notification time compared to MHS without such agreements.</p> <p>Conclusions</p> <p>Over the study period, many cases of the six notifiable diseases were not reported within two incubation periods, and many were reported more than three days after laboratory diagnosis. An increase in direct laboratory reporting of diagnoses to MHS would improve timeliness, as would the use of fax rather than post or e-mail. Automated reporting systems have to be explored in the Netherlands. Development of standardised and improved measures for timeliness is needed.</p
ΠΠ»ΠΈΠ½ΠΈΡΠ΅ΡΠΊΠΈΠ΅, Π³Π΅ΠΌΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΠΈ Π±ΠΈΠΎΡ ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΡΡΡΠ΅ΠΊΡΡ ΡΠ°ΠΌΠΈΠΏΡΠΈΠ»Π° Ρ Π±ΠΎΠ»ΡΠ½ΡΡ ΡΠ°Ρ Π°ΡΠ½ΡΠΌ Π΄ΠΈΠ°Π±Π΅ΡΠΎΠΌ 2-Π³ΠΎ ΡΠΈΠΏΠ° ΠΈ Π°ΡΡΠ΅ΡΠΈΠ°Π»ΡΠ½ΠΎΠΉ Π³ΠΈΠΏΠ΅ΡΡΠ΅Π½Π·ΠΈΠ΅ΠΉ
ΠΠ·ΡΡΠ΅Π½Ρ ΠΊΠ»ΠΈΠ½ΠΈΡΠ΅ΡΠΊΠΈΠ΅, Π³Π΅ΠΌΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΠΈ Π±ΠΈΠΎΡ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΡΡΡΠ΅ΠΊΡΡ ΡΠ°ΠΌΠΈΠΏΡΠΈΠ»Π° Ρ Π±ΠΎΠ»ΡΠ½ΡΡ
ΡΠ°Ρ
Π°ΡΠ½ΡΠΌ Π΄ΠΈΠ°Π±Π΅ΡΠΎΠΌ 2βΠ³ΠΎ ΡΠΈΠΏΠ° ΠΈ Π°ΡΡΠ΅ΡΠΈΠ°Π»ΡΠ½ΠΎΠΉ Π³ΠΈΠΏΠ΅ΡΡΠ΅Π½Π·ΠΈΠ΅ΠΉ.ΠΠΈΠ²ΡΠ΅Π½ΠΎ ΠΊΠ»ΡΠ½ΡΡΠ½Ρ, Π³Π΅ΠΌΠΎΠ΄ΠΈΠ½Π°ΠΌΡΡΠ½Ρ ΡΠ° Π±ΡΠΎΡ
ΡΠΌΡΡΠ½Ρ Π΅ΡΠ΅ΠΊΡΠΈ ΡΠ°ΠΌΡΠΏΡΠΈΠ»Ρ Ρ Ρ
Π²ΠΎΡΠΈΡ
Π½Π° ΡΡΠΊΡΠΎΠ²ΠΈΠΉ Π΄ΡΠ°Π±Π΅Ρ 2βΠ³ΠΎ ΡΠΈΠΏΡ ΡΠ° Π°ΡΡΠ΅ΡΡΠ°Π»ΡΠ½Ρ Π³ΡΠΏΠ΅ΡΡΠ΅Π½Π·ΡΡ.Clinical, hemodynamic, and biochemical effects of Ramipril were investigated in patients with type 2 diabetes mellitus and arterial hypertension
The effect of competition between health opinions on epidemic dynamics
Past major epidemic events showed that when an infectious disease is perceived to cause severe health outcomes, individuals modify health behavior affecting epidemic dynamics. To investigate the effect of this feedback relationship on epidemic dynamics, we developed a compartmental model that couples a disease spread framework with competition of two mutually exclusive health opinions (health-positive and health-neutral) associated with different health behaviors. The model is based on the assumption that individuals switch health opinions as a result of exposure to opinions of others through interpersonal communications. To model opinion switch rates, we considered a family of functions and identified the ones that allow health opinions to coexist. Finally, the model includes assortative mixing by opinions. In the disease-free population, either the opinions cannot coexist and one of them is always dominating (mono-opinion equilibrium) or there is at least one stable coexistence of opinions equilibrium. In the latter case, there is multistability between the coexistence equilibrium and the two mono-opinion equilibria. When two opinions coexist, it depends on their distribution whether the infection can invade. If presence of the infection leads to increased switching to a health-positive opinion, the epidemic burden becomes smaller than indicated by the basic reproduction number. Additionally, a feedback between epidemic dynamics and health opinion dynamics may result in (sustained) oscillatory dynamics and a switch to a different stable opinion distribution. Our model captures feedback between spread of awareness through social interactions and infection dynamics and can serve as a basis for more elaborate individual-based models
Controlling the pandemic during the SARS-CoV-2 vaccination rollout
Β© The Author(s) 2021. Open Access. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the articleβs Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the articleβs Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.There is a consensus that mass vaccination against SARS-CoV-2 will ultimately end the COVID-19 pandemic. However, it is not clear when and which control measures can be relaxed during the rollout of vaccination programmes. We investigate relaxation scenarios using an age-structured transmission model that has been fitted to age-specific seroprevalence data, hospital admissions, and projected vaccination coverage for Portugal. Our analyses suggest that the pressing need to restart socioeconomic activities could lead to new pandemic waves, and that substantial control efforts prove necessary throughout 2021. Using knowledge on control measures introduced in 2020, we anticipate that relaxing measures completely or to the extent as in autumn 2020 could launch a wave starting in April 2021. Additional waves could be prevented altogether if measures are relaxed as in summer 2020 or in a step-wise manner throughout 2021. We discuss at which point the control of COVID-19 would be achieved for each scenario.G.R., J.V., A.N., M.C.G. were supported by Fundação para a CiΓͺncia e a Tecnologia (FCT) project reference 131_596787873, awarded to G.R. M.V. was supported by the European Union H2020 ERA project (No. 667824 - EXCELLtoINNOV). The contribution of C.H.v.D. was under the auspices of the US Department of Energy (contract number 89233218CNA000001) and supported by the National Institutes of Health (grant number R01-OD011095). MK acknowledges support from the Netherlands Organization for Health Research and Development (ZonMw) Grant no. 10430022010001.info:eu-repo/semantics/publishedVersio
An evidence synthesis approach to estimating the incidence of seasonal influenza in the Netherlands.
OBJECTIVES: To estimate, using Bayesian evidence synthesis, the age-group-specific annual incidence of symptomatic infection with seasonal influenza in the Netherlands over the period 2005-2007. METHODS: The Netherlands population and age group distribution for 2006 defined the base population. The number of influenza-like illness (ILI) cases was estimated from sentinel surveillance data and adjusted for underascertainment using the estimated proportion of ILI cases that do not consult a general practitioner. The estimated number of symptomatic influenza (SI) cases was based on indirect evidence from the surveillance of ILI cases and the proportions of laboratory-confirmed influenza cases in the 2004/5, 2005/6 and 2006/7 respiratory years. In scenario analysis, the number of SI cases prevented by increasing vaccination uptake within the 65Β +Β age group was estimated. RESULTS: The overall symptomatic infection attack rate (SIAR) over the period 2005-2007 was estimated at 2Β·5% (95% credible interval [CI]: 2Β·1-3Β·2%); 410Β 200 SI cases (95% CI: 338Β 500-518Β 600) were estimated to occur annually. Age-group-specific SIARs were estimated for <5Β years at 4Β·9% (2Β·1-13Β·7%), for 5-14Β years at 3Β·0% (2Β·0-4Β·7%), for 15-44Β years at 2Β·6% (2Β·1-3Β·2%), for 45-64Β years at 1Β·9% (1Β·4-2Β·5%) and for 65Β +Β years at 1Β·7% (1Β·0-3Β·0%). Under assumed vaccination uptake increases of 5% and 15%, 1970 and 5310 SI cases would be averted. CONCLUSIONS: By synthesising the available information on seasonal influenza and ILI from diverse sources, the annual extent of symptomatic infection can be derived. These estimates are useful for assessing the burden of seasonal influenza and for guiding vaccination policy
ΠΠ»ΠΈΡΠ½ΠΈΠ΅ Π»Π΅Π΄ΠΎΠ²ΠΎΠ³ΠΎ ΡΠΆΠ°ΡΠΈΡ Π½Π° ΡΠΎΡΡΠ°Π²Π»ΡΡΡΠΈΠ΅ ΡΠΊΠΎΡΠΎΡΡΠΈ Π΄Π²ΠΈΠΆΠ΅Π½ΠΈΡ ΠΆΠΈΠ΄ΠΊΠΎΡΡΠΈ ΠΏΠΎΠ΄ Π»Π΅Π΄ΡΠ½ΡΠΌ ΠΏΠΎΠΊΡΠΎΠ²ΠΎΠΌ Π² Π±Π΅Π³ΡΡΠ΅ΠΉ ΠΏΠ΅ΡΠΈΠΎΠ΄ΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΈΠ·Π³ΠΈΠ±Π½ΠΎ-Π³ΡΠ°Π²ΠΈΡΠ°ΡΠΈΠΎΠ½Π½ΠΎΠΉ Π²ΠΎΠ»Π½Π΅ ΠΊΠΎΠ½Π΅ΡΠ½ΠΎΠΉ Π°ΠΌΠΏΠ»ΠΈΡΡΠ΄Ρ
ΠΠ΅ΡΠΎΠ΄ΠΎΠΌ ΠΌΠ½ΠΎΠ³ΠΈΡ
ΠΌΠ°ΡΡΡΠ°Π±ΠΎΠ² Ρ ΡΠΎΡΠ½ΠΎΡΡΡΡ Π΄ΠΎ Π²Π΅Π»ΠΈΡΠΈΠ½ ΡΡΠ΅ΡΡΠ΅Π³ΠΎ ΠΏΠΎΡΡΠ΄ΠΊΠ° ΠΌΠ°Π»ΠΎΡΡΠΈ ΠΏΠΎΠ»ΡΡΠ΅Π½Ρ Π°ΡΠΈΠΌΠΏΡΠΎΡΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΡΠ°Π·Π»ΠΎΠΆΠ΅Π½ΠΈΡ, ΠΎΠΏΡΠ΅Π΄Π΅Π»ΡΡΡΠΈΠ΅ ΡΠΎΡΡΠ°Π²Π»ΡΡΡΠΈΠ΅ ΡΠΊΠΎΡΠΎΡΡΠΈ Π΄Π²ΠΈΠΆΠ΅Π½ΠΈΡ ΠΆΠΈΠ΄ΠΊΠΎΡΡΠΈ ΠΏΠΎΠ΄ ΠΏΠ»Π°Π²Π°ΡΡΠΈΠΌ Π»Π΅Π΄ΡΠ½ΡΠΌ ΠΏΠΎΠΊΡΠΎΠ²ΠΎΠΌ ΠΏΡΠΈ ΡΠ°ΡΠΏΡΠΎΡΡΡΠ°Π½Π΅Π½ΠΈΠΈ ΠΏΠ΅ΡΠΈΠΎΠ΄ΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠ½ΠΎΠΉ ΠΈΠ·Π³ΠΈΠ±Π½ΠΎΠ³ΡΠ°Π²ΠΈΡΠ°ΡΠΈΠΎΠ½Π½ΠΎΠΉ Π²ΠΎΠ»Π½Ρ ΠΊΠΎΠ½Π΅ΡΠ½ΠΎΠΉ Π°ΠΌΠΏΠ»ΠΈΡΡΠ΄Ρ Π² ΡΡΠ»ΠΎΠ²ΠΈΡΡ
Π»Π΅Π΄ΠΎΠ²ΠΎΠ³ΠΎ ΡΠΆΠ°ΡΠΈΡ. Π Π°ΡΡΠΌΠΎΡΡΠ΅Π½Π° Π·Π°Π²ΠΈΡΠΈΠΌΠΎΡΡΡ ΡΠ°ΡΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΠΉ ΡΠΎΡΡΠ°Π²Π»ΡΡΡΠΈΡ
ΡΠΊΠΎΡΠΎΡΡΠΈ Π²Π΄ΠΎΠ»Ρ ΠΏΡΠΎΡΠΈΠ»Ρ Π²ΠΎΠ»Π½Ρ ΠΎΡ Π²Π΅Π»ΠΈΡΠΈΠ½Ρ ΡΠΆΠΈΠΌΠ°ΡΡΠ΅Π³ΠΎ ΡΡΠΈΠ»ΠΈΡ ΠΈ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊ Π½Π°ΡΠ°Π»ΡΠ½ΠΎΠΉ Π³Π°ΡΠΌΠΎΠ½ΠΈΠΊΠΈ. ΠΠΎΠΊΠ°Π·Π°Π½ΠΎ, ΡΡΠΎ Ρ ΡΠ²Π΅Π»ΠΈΡΠ΅Π½ΠΈΠ΅ΠΌ ΡΠΆΠΈΠΌΠ°ΡΡΠ΅Π³ΠΎ ΡΡΠΈΠ»ΠΈΡ ΠΏΡΠΎΠΈΡΡ
ΠΎΠ΄ΠΈΡ ΡΠΌΠ΅Π½ΡΡΠ΅Π½ΠΈΠ΅ Π°ΠΌΠΏΠ»ΠΈΡΡΠ΄Π½ΡΡ
Π·Π½Π°ΡΠ΅Π½ΠΈΠΉ ΡΠΎΡΡΠ°Π²Π»ΡΡΡΠΈΡ
ΡΠΊΠΎΡΠΎΡΡΠΈ ΠΈ ΠΎΡΡΡΠ°Π²Π°Π½ΠΈΠ΅ ΡΠ°Π·Ρ ΠΊΠΎΠ»Π΅Π±Π°Π½ΠΈΠΉ.ΠΠ΅ΡΠΎΠ΄ΠΎΠΌ Π±Π°Π³Π°ΡΡΠΎΡ
ΠΌΠ°ΡΡΡΠ°Π±ΡΠ² Π· ΡΠΎΡΠ½ΡΡΡΡ Π΄ΠΎ Π²Π΅Π»ΠΈΡΠΈΠ½ ΡΡΠ΅ΡΡΠΎΠ³ΠΎ ΠΏΠΎΡΡΠ΄ΠΊΡ ΠΌΠ°Π»ΠΎΡΡΡ ΠΎΡΡΠΈΠΌΠ°Π½Ρ Π°ΡΠΈΠΌΠΏΡΠΎΡΠΈΡΠ½Ρ ΡΠΎΠ·ΠΊΠ»Π°Π΄Π°Π½Π½Ρ, ΡΠΊΡ Π²ΠΈΠ·Π½Π°ΡΠ°ΡΡΡ ΡΠΊΠ»Π°Π΄ΠΎΠ²Ρ ΡΠ²ΠΈΠ΄ΠΊΠΎΡΡΡ ΡΡΡ
Ρ ΡΡΠ΄ΠΈΠ½ΠΈ ΠΏΡΠ΄ ΠΏΠ»Π°Π²Π°ΡΡΠΈΠΌ Π»ΡΠΎΠ΄ΡΠ½ΠΈΠΌ ΠΏΠΎΠΊΡΠΈΠ²ΠΎΠΌ ΠΏΡΠΈ ΡΠΎΠ·ΠΏΠΎΠ²ΡΡΠ΄ΠΆΠ΅Π½Π½Ρ ΠΏΠ΅ΡΡΠΎΠ΄ΠΈΡΠ½ΠΎΡ ΠΏΠΎΠ²Π΅ΡΡ
Π½Π΅Π²ΠΎΡ Π·Π³ΠΈΠ½Π°Π»ΡΠ½ΠΎ-Π³ΡΠ°Π²ΡΡΠ°ΡΡΠΉΠ½ΠΎΡ Ρ
Π²ΠΈΠ»Ρ ΠΊΡΠ½ΡΠ΅Π²ΠΎΡ Π°ΠΌΠΏΠ»ΡΡΡΠ΄ΠΈ Π² ΡΠΌΠΎΠ²Π°Ρ
Π»ΡΠΎΠ΄ΡΠ½ΠΎΠ³ΠΎ ΡΡΠΈΡΠ½Π΅Π½Π½Ρ. Π ΠΎΠ·Π³Π»ΡΠ½ΡΡΠΎ Π·Π°Π»Π΅ΠΆΠ½ΡΡΡΡ ΡΠΎΠ·ΠΏΠΎΠ΄ΡΠ»ΡΠ² ΡΠΊΠ»Π°Π΄ΠΎΠ²ΠΈΡ
ΡΠ²ΠΈΠ΄ΠΊΠΎΡΡΡ Π²Π·Π΄ΠΎΠ²ΠΆ ΠΏΡΠΎΡΡΠ»Ρ Ρ
Π²ΠΈΠ»Ρ Π²ΡΠ΄ Π²Π΅Π»ΠΈΡΠΈΠ½ΠΈ ΡΡΠΈΡΠΊΠ°ΡΡΠΎΠ³ΠΎ Π·ΡΡΠΈΠ»Π»Ρ ΡΠ° Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊ ΠΏΠΎΡΠ°ΡΠΊΠΎΠ²ΠΎΡ Π³Π°ΡΠΌΠΎΠ½ΡΠΊΠΈ. ΠΠΎΠΊΠ°Π·Π°Π½ΠΎ, ΡΠΎ ΡΠ· Π·Π±ΡΠ»ΡΡΠ΅Π½Π½ΡΠΌ ΡΡΠΈΡΠΊΠ°ΡΡΠΎΠ³ΠΎ Π·ΡΡΠΈΠ»Π»Ρ Π²ΡΠ΄Π±ΡΠ²Π°ΡΡΡΡΡ Π·ΠΌΠ΅Π½ΡΠ΅Π½Π½Ρ Π°ΠΌΠΏΠ»ΡΡΡΠ΄Π½ΠΈΡ
Π·Π½Π°ΡΠ΅Π½Ρ ΡΠΊΠ»Π°Π΄ΠΎΠ²ΠΈΡ
ΡΠ²ΠΈΠ΄ΠΊΠΎΡΡΡ ΡΠ° Π²ΡΠ΄ΡΡΠ°Π²Π°Π½Π½Ρ ΡΠ°Π·ΠΈ ΠΊΠΎΠ»ΠΈΠ²Π°Π½Ρ.Using the method of multiple scales, the asymptotic expansions are obtained up to the values of the third order. The expansions condition the components of fluid movement velocity under floating ice cover at propagation of periodic surface flexural-gravity wave of finite amplitude in the condition of ice compression. Dependence of distribution of velocity components along the wave profile upon the compressive force value and the initial harmonic characteristics is considered. It is shown that rise of compressive force is accompanied by decrease of amplitude values of velocity components and lag of oscillationsβ phase
Clustering of chronic hepatitis B screening intentions in social networks of Moroccan immigrants in the Netherlands
Background Early detection, identification, and treatment of chronic hepatitis B through screening is vital for those at increased risk, e.g. born in hepatitis B endemic countries. In the Netherlands, Moroccan immigrants show low participation rates in health-related screening programmes. Since social networks influence health behaviour, we investigated whether similar screening intentions for chronic hepatitis B cluster within social networks of Moroccan immigrants. Methods We used respondent-driven sampling (RDS) where each participant ("recruiter") was asked to complete a questionnaire and to recruit three Moroccans ("recruitees") from their social network. Logistic regression analyses were used to analyse whether the recruiters' intention to request a screening test was similar to the intention of their recruitees. Results We sampled 354 recruiter-recruitee pairs: for 154 pairs both participants had a positive screening intention, for 68 pairs both had a negative screening intention, and the remaining 132 pairs had a discordant intention to request a screening test. A tie between a recruiter and recruitee was associated with having the same screening intention, after correction for sociodemographic variables (OR 1.70 [1.15-2.51]). Conclusions The findings of our pilot study show clustering of screening intention among individuals in the same network. This provides opportunities for social network interventions to encourage participation in hepatitis B screening initiatives
Challenges for modelling interventions for future pandemics
Funding: This work was supported by the Isaac Newton Institute (EPSRC grant no. EP/R014604/1). MEK was supported by grants from The Netherlands Organisation for Health Research and Development (ZonMw), grant number 10430022010001, and grant number 91216062, and by the H2020 Project 101003480 (CORESMA). RNT was supported by the UKRI, grant number EP/V053507/1. GR was supported by Fundação para a CiΓͺncia e a Tecnologia (FCT) project reference 131_596787873. and by the VERDI project 101045989 funded by the European Union. LP and CO are funded by the Wellcome Trust and the Royal Society (grant 202562/Z/16/Z). LP is also supported by the UKRI through the JUNIPER modelling consortium (grant number MR/V038613/1) and by The Alan Turing Institute for Data Science and Artificial Intelligence. HBS is funded by the Wellcome Trust and Royal Society (202562/Z/16/Z), and the Alexander von Humboldt Foundation. DV had support from the National Council for Scientific and Technological Development of Brazil (CNPq - Refs. 441057/2020-9, 424141/2018-3, 309569/2019-2). FS is supported by the UKRI through the JUNIPER modelling consortium (grant number MR/V038613/1). EF is supported by UKRI (Medical Research Council)/Department of Health and Social Care (National Insitute of Health Research) MR/V028618/1. JPG's work was supported by funding from the UK Health Security Agency and the UK Department of Health and Social Care.Mathematical modelling and statistical inference provide a framework to evaluate different non-pharmaceutical and pharmaceutical interventions for the control of epidemics that has been widely used during the COVID-19 pandemic. In this paper, lessons learned from this and previous epidemics are used to highlight the challenges for future pandemic control. We consider the availability and use of data, as well as the need for correct parameterisation and calibration for different model frameworks. We discuss challenges that arise in describing and distinguishing between different interventions, within different modelling structures, and allowing both within and between host dynamics. We also highlight challenges in modelling the health economic and political aspects of interventions. Given the diversity of these challenges, a broad variety of interdisciplinary expertise is needed to address them, combining mathematical knowledge with biological and social insights, and including health economics and communication skills. Addressing these challenges for the future requires strong cross-disciplinary collaboration together with close communication between scientists and policy makers.Publisher PDFPeer reviewe
Impact of delays on effectiveness of contact tracing strategies for COVID-19: a modelling study
Background In countries with declining numbers of confirmed cases of COVID-19, lockdown measures are gradually being lifted. However, even if most physical distancing measures are continued, other public health measures will be needed to control the epidemic. Contact tracing via conventional methods or mobile app technology is central to control strategies during de-escalation of physical distancing. We aimed to identify key factors for a contact tracing strategy to be successful. Methods We evaluated the impact of timeliness and completeness in various steps of a contact tracing strategy using a stochastic mathematical model with explicit time delays between time of infection and symptom onset, and between symptom onset, diagnosis by testing, and isolation (testing delay). The model also includes tracing of close contacts (eg, household members) and casual contacts, followed by testing regardless of symptoms and isolation if testing positive, with different tracing delays and coverages. We computed effective reproduction numbers of a contact tracing strategy (RCTS) for a population with physical distancing measures and various scenarios for isolation of index cases and tracing and quarantine of their contacts. Findings For the most optimistic scenario (testing and tracing delays of 0 days and tracing coverage of 100%), and assuming that around 40% of transmissions occur before symptom onset, the model predicts that the estimated effective reproduction number of 1Β·2 (with physical distancing only) will be reduced to 0Β·8 (95% CI 0Β·7β0Β·9) by adding contact tracing. The model also shows that a similar reduction can be achieved when testing and tracing coverage is reduced to 80% (RCTS 0Β·8, 95% CI 0Β·7β1Β·0). A testing delay of more than 1 day requires the tracing delay to be at most 1 day or tracing coverage to be at least 80% to keep RCTS below 1. With a testing delay of 3 days or longer, even the most efficient strategy cannot reach RCTS values below 1. The effect of minimising tracing delay (eg, with app-based technology) declines with decreasing coverage of app use, but app-based tracing alone remains more effective than conventional tracing alone even with 20% coverage, reducing the reproduction number by 17Β·6% compared with 2Β·5%. The proportion of onward transmissions per index case that can be prevented depends on testing and tracing delays, and given a 0-day tracing delay, ranges from up to 79Β·9% with a 0-day testing delay to 41Β·8% with a 3-day testing delay and 4Β·9% with a 7-day testing delay. Interpretation In our model, minimising testing delay had the largest impact on reducing onward transmissions. Optimising testing and tracing coverage and minimising tracing delays, for instance with app-based technology, further enhanced contact tracing effectiveness, with the potential to prevent up to 80% of all transmissions. Access to testing should therefore be optimised, and mobile app technology might reduce delays in the contact tracing process and optimise contact tracing coverage. Funding ZonMw, Fundação para a CiΓͺncia e a Tecnologia, and EU Horizon 2020 RECOVER
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