Lessons learnt from 288 COVID-19 international cases: importations over time, effect of interventions, underdetection of imported cases

Abstract

288 cases have been confirmed out of China from January 3 to February 13, 2020. We collected and synthesized all available information on these cases from official sources and media. We analyzed importations that were successfully isolated and those leading to onward transmission. We modeled their number over time, in relation to the origin of travel (Hubei province, other Chinese provinces, other countries) and interventions. We characterized importations timeline to assess the rapidity of isolation, and epidemiologically linked clusters to estimate the rate of detection. We found a rapid exponential growth of importations from Hubei, combined with a slower growth from the other areas. We predicted a rebound of importations from South East Asia in the upcoming weeks. Time from travel to detection has considerably decreased since the first importation, however 6 cases out of 10 were estimated to go undetected. Countries outside China should be prepared for the possible emergence of several undetected clusters of chains of local transmissions.

Accommodating individual travel history, global mobility, and unsampled diversity in phylogeography: a SARS-CoV-2 case study

“…The time dependency imposed by travel restrictions could potentially be modelled with an epoch version of the discrete trait CTMC 25 . This could also be important for the asymmetry factor we included for transitions from Hubei as these will be severely impacted by the travel ban imposed on January 23 45 . Finally, in addition to investigating the impact of model and data adjustments on empirical examples, simulation studies would greatly assist in evaluating the performance of the phylogeographic reconstructions in controlled scenarios.…”

Genomic Analysis of Early SARS-CoV-2 Variants Introduced in Mexico

“…This is the third outbreak related to zoonotic betacoronaviruses known to have occurred in humans in the last 2 decades, after SARS (severe acute respiratory syndrome) in 2002 and MERS (Middle East respiratory syndrome) in 2012. After its emergence in China, SARS-CoV-2 was spread initially to other parts of the world by people with a travel history to China but gradually shifted to local transmissions (LTs) (3). Viral spread was first detected in Thailand, South Korea, and Japan, and by the second half of January, the first positive cases appeared in the United States and Europe (France, Italy, and Spain).…”

Digital Proximity Tracing in the COVID-19 Pandemic on Empirical Contact Networks

“…We remark that this is the setting considered in the previous studies of this model. 1,3 Next, we assume instead that 40% of infected individuals are asymptomatic 1,31,32,60,61 and that only symptomatic individuals are identified: no randomized testing is performed. We represent asymptomatics by considering that the probability of an infected individual to display symptoms is a growing function of time that never reaches the value 1.…”

“…While the testing and isolation of symptomatic cases is certainly crucial, it is insufficient in the case of SARS-CoV-2, since there is clear evidence of presymptomatic transmission, 1,29,30 and a fraction of infected individuals do not develop symptoms at all. 31,32 Thus, the identification and isolation of infected cases must be coupled with a strategy for tracing their contacts who may have become infected. That way, contacts who may pass on the infection before the onset of symptoms, can then be quarantined and their health status monitored.…”