Assessing spread risk of COVID-19 in early 2020

A novel coronavirus emerged in late 2019,named as the coronavirus disease 2019(COVID-19)by the World Health Organization(WHO).This study was originally conducted in January 2020 to estimate the potential risk and geographic range of COVID-19 spread at the early stage of the transmission.A series of connectivity and risk analyses based on domestic and international travel networks were conducted using historical aggregated mobile phone data and air passenger itinerary data.We found that the cordon sanitaire of the primary city was likely to have occurred during the latter stages of peak population numbers leaving the city,with travellers departing into neighbouring cities and other megacities in China.We estimated that there were 59,912 international air passengers,of which 834(95%uncertainty interval:478–1,349)had COVID-19 infection,with a strong correlation seen between the predicted risks of importation and the number of imported cases found.Given the limited understanding of emerging infectious diseases in the very early stages of outbreaks,our approaches and findings in assessing travel patterns and risk of transmission can help guide public health preparedness and intervention design for new COVID-19 waves caused by variants of concern and future pandemics to effectively limit transmission beyond its initial extent.

Redefining pandemic preparedness:Multidisciplinary insights from the CERP modelling workshop in infectious diseases,workshop report

In July 2023,the Center of Excellence in Respiratory Pathogens organized a two-day workshop on infectious diseases modelling and the lessons learnt from the Covid-19 pandemic.This report summarizes the rich discussions that occurred during the workshop.The workshop participants discussed multisource data integration and highlighted the benefits of combining traditional surveillance with more novel data sources like mobility data,social media,and wastewater monitoring.Significant advancements were noted in the development of predictive models,with examples from various countries showcasing the use of machine learning and artificial intelligence in detecting and monitoring disease trends.The role of open collaboration between various stakeholders in modelling was stressed,advocating for the continuation of such partnerships beyond the pandemic.A major gap identified was the absence of a common international framework for data sharing,which is crucial for global pandemic preparedness.Overall,the workshop underscored the need for robust,adaptable modelling frameworks and the integration of different data sources and collaboration across sectors,as key elements in enhancing future pandemic response and preparedness.

Relatedness of the incidence decay with exponential adjustment(IDEA)model,“Farr's law”and SIR compartmental difference equation models

Mathematical models are often regarded as recent innovations in the description and analysis of infectious disease outbreaks and epidemics,but simple mathematical expressions have been in use for projection of epidemic trajectories for more than a century.We recently introduced a single equation model(the incidence decay with exponential adjustment,or IDEA model)that can be used for short-term epidemiological forecasting.In the mid-19th century,Dr.William Farr made the observation that epidemic events rise and fall in a roughly symmetrical pattern that can be approximated by a bell-shaped curve.He noticed that this time-evolution behavior could be captured by a single mathematical formula(“Farr's law”)that could be used for epidemic forecasting.We show here that the IDEA model follows Farr's law,and show that for intuitive assumptions,Farr's Law can be derived from the IDEA model.Moreover,we show that both mathematical approaches,Farr's Law and the IDEA model,resemble solutions of a susceptible-infectious-removed(SIR)compartmental differential-equation model in an asymptotic limit,where the changes of disease transmission respond to control measures,and not only to the depletion of susceptible individuals.This suggests that the concept of the reproduction number eR 0T was implicitly captured in Farr's(pre-microbial era)work,and also suggests that control of epidemics,whether via behavior change or intervention,is as integral to the natural history of epidemics as is the dynamics of disease transmission.

Countries at risk of importation of chikungunya virus cases from Southern Thailand: A modeling study

Southern Thailand has been experiencing a large chikungunya virus(CHIKV)outbreak since October 2018.Given the magnitude and duration of the outbreak and its location in a popular tourist destination,we sought to determine international case exportation risk and identify countries at greatest risk of receiving travel-associated imported CHIKV cases.We used a probabilistic model to estimate the expected number of exported cases from Southern Thailand between October 2018 and April 2019.The model incorporated data on CHIKV natural history,infection rates in Southern Thailand,average length of stay for tourists,and international outbound air passenger numbers from the outbreak area.For countries highly connected to Southern Thailand by air travel,we ran 1000 simulations to estimate the expected number of imported cases.We also identified destination countries with conditions suitable for autochthonous CHIKV transmission.Over the outbreak period,we estimated that an average of 125(95%credible interval(CrI):102e149)cases would be exported from Southern Thailand to international destinations via air travel.China was projected to receive the most cases(43,95%CrI:30e56),followed by Singapore(7,95%CrI:2e12)and Malaysia(5,95%CrI:1e10).Twenty-three countries were projected to receive at least one imported case,and 64%of these countries had one or more regions that could potentially support autochthonous CHIKV transmission.The overall risk of international exportation of CHIKV cases associated with the outbreak is Southern Thailand is high.Our model projections are consistent with recent reports of CHIKV in travelers returning from the region.Countries should be alert to the possibility of CHIKV infection in returning travelers,particularly in regions where autochthonous transmission is possible.