LitCovid-sentences  

PMC:7060038 / 34496-46302 JSONTXT 13 Projects

Annnotations TAB TSV DIC JSON TextAE

Id Subject Object Predicate Lexical cue
T219 0-10 Sentence denotes Discussion
T220 11-278 Sentence denotes The international expansion of COVID-19 cases has led to widespread adoption of symptom and risk screening measures, in travel-associated and other contexts, and programs may still be adopted or expanded as source epidemics of COVID-19 emerge in new geographic areas.
T221 279-610 Sentence denotes Using a mathematical model of screening effectiveness, with preliminary estimates of COVID-19 epidemiology and natural history, we estimate that screening will detect less than half of infected travellers in a growing epidemic, and that screening effectiveness will increase marginally as growth of the source epidemic decelerates.
T222 611-684 Sentence denotes We found that two main factors influenced the effectiveness of screening.
T223 685-858 Sentence denotes First, symptom screening depends on the natural history of an infection: individuals are increasingly likely to show detectable symptoms with increasing time since exposure.
T224 859-1107 Sentence denotes A fundamental shortcoming of screening is the difficulty of detecting infected individuals during their incubation period, or early after the onset of symptoms, at which point they still feel healthy enough to undertake normal activities or travel.
T225 1108-1292 Sentence denotes This difficulty is amplified when the incubation period is longer; infected individuals have a longer window in which they may mix socially or travel with low probability of detection.
T226 1293-1446 Sentence denotes Second, screening depends on whether exposure risk factors exist that would facilitate specific and reasonably sensitive case detection by questionnaire.
T227 1447-1612 Sentence denotes For COVID-19, there is so far limited evidence for specific risk factors; we therefore assumed that at most 40% of travellers would be aware of a potential exposure.
T228 1613-1848 Sentence denotes It is plausible that many individuals aware of a potential exposure would voluntarily avoid travel and practice social distancing--if so, the population of infected travellers will be skewed toward those unaware they have been exposed.
T229 1849-2087 Sentence denotes Furthermore, based on screening outcomes during the 2009 influenza pandemic, we assumed that a minority of infected travellers would self-report their exposure honestly, which led to limited effectiveness in questionnaire-based screening.
T230 2088-2198 Sentence denotes The confluence of these two factors led to many infected people being fundamentally undetectable in our model.
T231 2199-2366 Sentence denotes Even under our most generous assumptions about the natural history of COVID-19, the presence of undetectable cases made the greatest contribution to screening failure.
T232 2367-2497 Sentence denotes Correctable failures, such as missing an infected person with fever or awareness of their exposure risk, played a more minor role.
T233 2498-2834 Sentence denotes Our conclusion that screening would detect no more than half of infected travellers in a growing epidemic is consistent with recent studies that have compared country-specific air travel volumes with detected case counts to estimate that roughly two thirds of imported cases remain undetected (Niehus et al., 2020; Bhatia et al., 2020).
T234 2835-2982 Sentence denotes Furthermore, the finding that the majority of cases missed by screening are fundamentally undetectable is consistent with observed outcomes so far.
T235 2983-3275 Sentence denotes Analyzing a line list of 290 cases imported into various countries (Dorigatti et al., 2020), we found that symptom onset occurred after the date of inbound travel for 72% (75/104) of cases for whom both dates were available, and a further 14% (15/104) had symptom onset on the date of travel.
T236 3276-3668 Sentence denotes Even among passengers of repatriation flights, or quarantined on a cruise ship off the coast of Japan (who are all demonstrably at high risk), numerous cases have been undetectable in symptom screening, but have still tested positive for SARS-CoV-2 by PCR (Dorigatti et al., 2020; Hoehl et al., 2020; Japan Ministry of Health, Labor and Welfare, 2020; Nishiura et al., 2020; Hu et al., 2020).
T237 3669-3870 Sentence denotes The onset of viral shedding prior to the onset of symptoms, or in cases that remain asymptomatic, is a classic factor that makes infectious disease outbreaks difficult to control (Fraser et al., 2004).
T238 3871-4058 Sentence denotes Our results emphasize that the true fraction of subclinical cases (those who lack fever or cough at symptom onset) remains a crucial unknown, and strongly impacts screening effectiveness.
T239 4059-4244 Sentence denotes Reviewing data from active surveillance of passengers on cruise ships or repatriation flights, we estimate that up to half of cases show no detectable symptoms at the time of diagnosis.
T240 4245-4337 Sentence denotes To complicate matters further, the fraction of subclinical cases may vary across age groups.
T241 4338-4577 Sentence denotes Children and young adults have been conspicuously underrepresented, even in very large clinical data sets (Chen et al., 2020; The Novel Coronavirus Pneumonia Emergency Response Epidemiology Team, 2020; Huang et al., 2020; Li et al., 2020).
T242 4578-4749 Sentence denotes Only 2.1% of the first 44,672 confirmed cases were observed in children under 20 years of age (The Novel Coronavirus Pneumonia Emergency Response Epidemiology Team, 2020).
T243 4750-4856 Sentence denotes The possibility cannot be ruled out that large numbers of subclinical cases are occurring in young people.
T244 4857-5011 Sentence denotes If an age-by-severity interaction does indeed exist, then the mean age of travellers should be taken into account when estimating screening effectiveness.
T245 5012-5055 Sentence denotes There are some limitations to our analysis.
T246 5056-5297 Sentence denotes Parameter values for COVID-19 may be affected by bias or censoring, particularly in the early stages of an outbreak when most cases have been recently infected, and when severe or hospitalized cases are overrepresented in the available data.
T247 5298-5433 Sentence denotes In particular, the tail of the incubation period distribution is difficult to characterize with precision using limited or biased data.
T248 5434-5584 Sentence denotes As country-specific screening policies can change rapidly in real-time, we focused on a general screening framework rather than specific case studies.
T249 5585-5656 Sentence denotes We also assumed traveller adherence and no active evasion of screening.
T250 5657-5828 Sentence denotes However, there are informal reports of people taking antipyretics to beat fever screening (Mahbubani, 2020), which would further reduce the effectiveness of these methods.
T251 5829-6027 Sentence denotes With travel restrictions in place, individuals may also take alternative routes (e.g. road rather than air), which would in effect circumvent departure and/or arrival screening as a control measure.
T252 6028-6130 Sentence denotes Our quantitative findings may overestimate screening effectiveness if many travellers evade screening.
T253 6131-6235 Sentence denotes Our results have several implications for the design and implementation of traveller screening policies.
T254 6236-6460 Sentence denotes If the infection is not yet present in a region, then arrival screening could delay the introduction of cases, but consistent with previous analyses, (Cowling et al., 2010), our results indicate such delays would be minimal.
T255 6461-6628 Sentence denotes Our findings indicate that for every case detected by travel screening, one or more infected travellers were not caught, and must be found and isolated by other means.
T256 6629-6832 Sentence denotes We note that even with high R0 and no control measures in place, a single case importation is not guaranteed to start a sustained chain of transmission (Kucharski et al., 2020; Lloyd-Smith et al., 2005).
T257 6833-7090 Sentence denotes This is particularly true for infections that exhibit a tendency toward superspreading events, as increasingly reported for COVID-19, but the flipside is that outbreaks triggered by superspreading are explosive when they do occur (Lloyd-Smith et al., 2005).
T258 7091-7185 Sentence denotes We did not analyze second-order benefits from screening, such as potential to raise awareness.
T259 7186-7418 Sentence denotes Official recommendations emphasize that screening is an opportunity for ‘risk communication’ in which travellers can be instructed how to proceed responsibly if symptoms develop at the destination (World Health Organization, 2020d).
T260 7419-7625 Sentence denotes Alongside increased general surveillance/alertness in healthcare settings, such measures could help reduce the risk of local transmission and superspreading, but their quantitative effectiveness is unknown.
T261 7626-7800 Sentence denotes Once limited local transmission has begun, arrival screening could still have merit as a means to restrict the number of parallel chains of transmission present in a country.
T262 7801-8013 Sentence denotes Once there is generalized spread which has outpaced contact tracing, departure screening to prevent export of cases to new areas will be more valuable than arrival screening to identify additional incoming cases.
T263 8014-8268 Sentence denotes Altogether, screening should not be viewed as a definitive barrier to case importation, but used alongside on-the-ground response strategies that help reduce the probability that any single imported case spreads to cause a self-sustaining local epidemic.
T264 8269-8463 Sentence denotes The cost-benefit tradeoff for any screening policy should be assessed in light of past experiences, where few or no infected travellers have been detected by such programs (Gostic et al., 2015).
T265 8464-8707 Sentence denotes While our findings indicate that the majority of screening failures arise from undetectable cases (i.e. those without symptoms or knowledge of their exposure), several factors could potentially strengthen the screening measures described here.
T266 8708-8942 Sentence denotes With improved efficiency of thermal scanners or other symptom detection technology, we would expect a smaller difference between the effectiveness of arrival-only screening and combined departure and arrival screening in our analysis.
T267 8943-9265 Sentence denotes Alternatively, the benefits of redundant screening (noted above for programs with departure and arrival screens) could be gained in a single-site screening program by simply having two successive fever-screening stations that travellers pass through (or taking multiple measurements of each traveller at a single station).
T268 9266-9368 Sentence denotes As risk factors become better known, questionnaires could be refined to identify more potential cases.
T269 9369-9610 Sentence denotes Alternatively, less stringent definition of high exposure risk (e.g. contact with anyone with respiratory symptoms) would be more sensitive, but at the expense of large numbers of false positives detained, especially during influenza season.
T270 9611-9784 Sentence denotes The availability of rapid PCR tests would also be beneficial for case identification at arrival, and would help address concerns with false-positive detections by screening.
T271 9785-10057 Sentence denotes If such tests were fast, there may be potential to test suspected cases in real time based on questionnaire responses, travel origin, or borderline symptoms; at least one PCR test for SARS-CoV-2 claimed to take less than an hour has already been announced (Biomeme, 2020).
T272 10058-10134 Sentence denotes However, such measures could prove highly expensive if implemented at scale.
T273 10135-10353 Sentence denotes There is also scope for new tools to improve the ongoing tracking of travellers who pass through screening, such as smartphone-based self-reporting of temperature or symptoms in incoming cases (Dorigatti et al., 2020).
T274 10354-10513 Sentence denotes Smartphone or diary-based surveillance would be cheaper and more scalable than intense, on-the-ground follow-up, but is likely to be limited by user adherence.
T275 10514-10825 Sentence denotes Our analysis underscores the reality that respiratory viruses are difficult to detect by symptom and risk screening programs, particularly if a substantial fraction of infected people show mild or indistinct symptoms, if incubation periods are long, and if transmission is possible before the onset of symptoms.
T276 10826-11016 Sentence denotes Quantitative estimates of screening effectiveness for COVID-19 will improve as more is learned about this recently-emerged virus, and will vary with the precise design of screening programs.
T277 11017-11282 Sentence denotes However, we present a robust qualitative finding: in any situation where there is widespread epidemic transmission in source populations from which travellers are drawn, travel screening programs can slow (marginally) but not stop the importation of infected cases.
T278 11283-11362 Sentence denotes Screening programs implemented in other settings will face the same challenges.
T279 11363-11548 Sentence denotes By decomposing the factors leading to success or failure of screening efforts, our work supports decision-making about program design, and highlights key questions for further research.
T280 11549-11806 Sentence denotes We hope that these insights may help to mitigate the global impacts of COVID-19 by guiding effective decision-making in both high- and low-resource countries, and may contribute to prospective improvements in screening policy for future emerging infections.