strategies to reduce the risk of sars cov 2 re introduction from international travellers CORD-Papers-2022-06-02 (Version 1)

Title: Strategies to reduce the risk of SARS-CoV-2 re-introduction from international travellers
Abstract: To mitigate SARS-CoV-2 transmission risks from international travellers many countries currently use a combination of up to 14 days of self-quarantine on arrival and testing for active infection. We used a simulation model of air travellers arriving to the UK from the EU or the USA and the timing of their stages of infection to evaluate the ability of these strategies to reduce the risk of seeding community transmission. We find that a quarantine period of 8 days on arrival with a PCR test on day 7 (with a 1-day delay for test results) can reduce the number of infectious arrivals released into the community by a median 94% compared to a no quarantine no test scenario. This reduction is similar to that achieved by a 14-day quarantine period (median 99% reduction). Shorter quarantine periods still can prevent a substantial amount of transmission; all strategies in which travellers spend at least 5 days (the mean incubation period) in quarantine and have at least one negative test before release are highly effective (e.g. a test on day 5 with release on day 6 results in a median 88% reduction in transmission potential). Without intervention the current high prevalence in the US (40 per 10000) results in a higher expected number of infectious arrivals per week (up to 23) compared to the EU (up to 12) despite an estimated 8 times lower volume of travel in July 2020. Requiring a 14-day quarantine period likely results in less than 1 infectious traveller each entering the UK per week from the EU and the USA (97.5th percentile). We also find that on arrival the transmission risk is highest from pre-symptomatic travellers; quarantine policies will shift this risk increasingly towards asymptomatic infections if eventually-symptomatic individuals self-isolate after the onset of symptoms. As passenger numbers recover strategies to reduce the risk of re-introduction should be evaluated in the context of domestic SARS-CoV-2 incidence preparedness to manage new outbreaks and the economic and psychological impacts of quarantine.
Published: 2020-07-24
DOI: 10.1101/2020.07.24.20161281
DOI_URL: http://doi.org/10.1101/2020.07.24.20161281
Author Name: Clifford S
Author link: https://covid19-data.nist.gov/pid/rest/local/author/clifford_s
Author Name: Quilty B J
Author link: https://covid19-data.nist.gov/pid/rest/local/author/quilty_b_j
Author Name: Russell T W
Author link: https://covid19-data.nist.gov/pid/rest/local/author/russell_t_w
Author Name: Liu Y
Author link: https://covid19-data.nist.gov/pid/rest/local/author/liu_y
Author Name: Chan Y W D
Author link: https://covid19-data.nist.gov/pid/rest/local/author/chan_y_w_d
Author Name: Pearson C A B
Author link: https://covid19-data.nist.gov/pid/rest/local/author/pearson_c_a_b
Author Name: Eggo R M
Author link: https://covid19-data.nist.gov/pid/rest/local/author/eggo_r_m
Author Name: Endo A
Author link: https://covid19-data.nist.gov/pid/rest/local/author/endo_a
Author Name: CMMID COVID Working Group
Author link: https://covid19-data.nist.gov/pid/rest/local/author/cmmid_covid_working_group
Author Name: Flasche S
Author link: https://covid19-data.nist.gov/pid/rest/local/author/flasche_s
Author Name: Edmunds W J
Author link: https://covid19-data.nist.gov/pid/rest/local/author/edmunds_w_j
Author Name: Sherratt, Katharine
Author link: https://covid19-data.nist.gov/pid/rest/local/author/sherratt_katharine
Author Name: Quaife, Matthew
Author link: https://covid19-data.nist.gov/pid/rest/local/author/quaife_matthew
Author Name: Bosse, Nikos I
Author link: https://covid19-data.nist.gov/pid/rest/local/author/bosse_nikos_i
Author Name: Medley, Graham
Author link: https://covid19-data.nist.gov/pid/rest/local/author/medley_graham
Author Name: Auzenbergs, Megan
Author link: https://covid19-data.nist.gov/pid/rest/local/author/auzenbergs_megan
Author Name: Kucharski, Adam J
Author link: https://covid19-data.nist.gov/pid/rest/local/author/kucharski_adam_j
Author Name: Davies, Nicholas G
Author link: https://covid19-data.nist.gov/pid/rest/local/author/davies_nicholas_g
Author Name: Brady, Oliver
Author link: https://covid19-data.nist.gov/pid/rest/local/author/brady_oliver
Author Name: Meakin, Sophie R
Author link: https://covid19-data.nist.gov/pid/rest/local/author/meakin_sophie_r
Author Name: Houben, Rein M G J
Author link: https://covid19-data.nist.gov/pid/rest/local/author/houben_rein_m_g_j
Author Name: Prem, Kiesha
Author link: https://covid19-data.nist.gov/pid/rest/local/author/prem_kiesha
Author Name: Julian Villabona-Arenas, C
Author link: https://covid19-data.nist.gov/pid/rest/local/author/julian_villabona_arenas_c
Author Name: Gibbs, Hamish P
Author link: https://covid19-data.nist.gov/pid/rest/local/author/gibbs_hamish_p
Author Name: Jombart, Thibaut
Author link: https://covid19-data.nist.gov/pid/rest/local/author/jombart_thibaut
Author Name: Diamond, Charlie
Author link: https://covid19-data.nist.gov/pid/rest/local/author/diamond_charlie
Author Name: Klepac, Petra
Author link: https://covid19-data.nist.gov/pid/rest/local/author/klepac_petra
Author Name: Deol, Arminder K
Author link: https://covid19-data.nist.gov/pid/rest/local/author/deol_arminder_k
Author Name: Lowe, Rachel
Author link: https://covid19-data.nist.gov/pid/rest/local/author/lowe_rachel
Author Name: Rudge, James W
Author link: https://covid19-data.nist.gov/pid/rest/local/author/rudge_james_w
Author Name: Funk, Sebastian
Author link: https://covid19-data.nist.gov/pid/rest/local/author/funk_sebastian
Author Name: Knight, Gwenan M
Author link: https://covid19-data.nist.gov/pid/rest/local/author/knight_gwenan_m
Author Name: Procter, Simon R
Author link: https://covid19-data.nist.gov/pid/rest/local/author/procter_simon_r
Author Name: Leclerc, Quentin J
Author link: https://covid19-data.nist.gov/pid/rest/local/author/leclerc_quentin_j
Author Name: Jarvis, Christopher I
Author link: https://covid19-data.nist.gov/pid/rest/local/author/jarvis_christopher_i
Author Name: Oreilly, Kathleen
Author link: https://covid19-data.nist.gov/pid/rest/local/author/oreilly_kathleen
Author Name: Hellewell, Joel
Author link: https://covid19-data.nist.gov/pid/rest/local/author/hellewell_joel
Author Name: Nightingale, Emily S
Author link: https://covid19-data.nist.gov/pid/rest/local/author/nightingale_emily_s
Author Name: Abbas, Kaja
Author link: https://covid19-data.nist.gov/pid/rest/local/author/abbas_kaja
sha: aeae83b3fc5c07dddb48347e3e835e574e9282a5
license: medrxiv
source_x: MedRxiv; WHO
source_x_url: https://www.who.int/
url: https://doi.org/10.1101/2020.07.24.20161281 http://medrxiv.org/cgi/content/short/2020.07.24.20161281v1?rss=1
has_full_text: TRUE
Keywords Extracted from Text Content: SARS-CoV-2 travellers UK self-quarantine people nasopharyngeal one-test pre-infectious persons medRxiv preprint Figure S2 upper US travellers medRxiv Fig 4B fly A. BA individuals self-quarantine friends persons traveller CAA medRxiv preprint Figure S1 NTS samples blue COVID-19 Travellers self-diagnose Quarantine medRxiv preprint https://doi.org/10.1101/2020.07.24.20161281 doi self-isolate tourist Figure 2 − Figure S5 -A https://doi.org/10.1101/2020.07 quarantine-based line SARS-CoV-2 (37) UK USD1.7tn per-individual NTS pre-infectious Per-individual Figure 2A post-arrival EU airlines ′ SARS-CoV-2 Centre
Extracted Text Content in Record: First 5000 Characters:To mitigate SARS-CoV-2 transmission risks from international travellers, many countries currently use a combination of up to 14 days of self-quarantine on arrival and testing for active infection. We used a simulation model of air travellers arriving to the UK from the EU or the USA and the timing of their stages of infection to evaluate the ability of these strategies to reduce the risk of seeding community transmission. We find that a quarantine period of 8 days on arrival with a PCR test on day 7 (with a 1-day delay for test results) can reduce the number of infectious arrivals released into the community by a median 94% compared to a no quarantine, no test scenario. This reduction is similar to that achieved by a 14-day quarantine period (median 99% reduction). Shorter quarantine periods still can prevent a substantial amount of transmission; all strategies in which travellers spend at least 5 days (the mean incubation period) in quarantine and have at least one negative test before release are highly effective (e.g. a test on day 5 with release on day 6 results in a median 88% reduction in transmission potential). Without intervention, the current high prevalence in the US (40 per 10,000) results in a higher expected number of infectious arrivals per week (up to 23) compared to the EU (up to 12), despite an estimated 8 times lower volume of travel in July 2020. Requiring a 14-day quarantine period likely results in less than 1 infectious traveller each entering the UK per week from the EU and the USA (97.5th percentile). We also find that on arrival the transmission risk is highest from pre-symptomatic travellers; quarantine policies will shift this risk increasingly towards asymptomatic infections if eventually-symptomatic individuals self-isolate after the onset of symptoms. As passenger numbers recover, strategies to reduce the risk of re-introduction should be evaluated in the context of domestic SARS-CoV-2 incidence, preparedness to manage new outbreaks, and the economic and psychological impacts of quarantine. With the introduction of non-pharmaceutical interventions (NPIs) such as physical distancing measures, many countries around the world have managed to curb local SARS-CoV-2 transmission and reduce the incidence of COVID-19 to sporadic cases and localised outbreaks. Under these circumstances, limiting reintroduction of infections from other countries becomes increasingly important in order to prevent additional outbreaks and avoid overwhelming resource-intensive control efforts. The current guideline in a number of countries is self-quarantine of new arrivals either at their home, with family or friends, or hotels or other temporary accommodation for 14 days (1) . It is expected that by day 14 at least 95% of eventually symptomatic cases have become symptomatic (2) . However, the median incubation period for SARS-CoV-2 is about 5 days (2) and, assuming that travellers are equally likely to travel at any point in that period, a 5-day quarantine on arrival should suffice to allow more than 50% of the infections to develop symptoms and be managed accordingly. Quarantine, either at home or at managed facilities, may lead to negative psychological effects stemming from social isolation (3, 4) and financial stress (5) . In addition, the continued application of COVID-19 related travel restrictions, including quarantine, is likely to significantly impact economies reliant on tourist and business travel. On 7 May 2020 the United Nations World Tourism Organisation estimated that up to 80% of the USD1.7tn global earnings from tourism in 2019 may be lost in 2020, along with 120m jobs (6). In an IATA survey, quarantine was cited as the primary reason for reluctance to travel (85%), along with fear of becoming infected (84%), with 17% of respondents unwilling to undergo quarantine (7) . Therefore, the anticipated personal, social and economic costs of extended quarantine must be justified by the reduction in transmission risk. As well as quarantine, some countries have introduced a requirement for travellers to undergo testing for SARS-CoV-2 infection with Reverse Transcription Polymerase Chain Reaction (RT-PCR, hereafter PCR). Such testing is, commonly, performed by taking nasopharyngeal or throat swabs (NTS) of individuals and analysing the resulting sample for the presence of SARS-CoV-2 RNA (8) . PCR screening may be conducted prior to the flight and/or upon arrival to allow detection of infected travellers on entry. Since 3 June 2020, Singapore has required visitors from China to take a PCR test no greater than 48-hours before departure, with a certificate of their infection-free status required for entry, and an additional test upon arrival (9) . A similar policy is in place in Hong Kong (10) ; travellers who test positive on arrival are transferred to hospital, while those who test negative enter a compulsory 14 day quarantine period at home or hotel, and in a managed quarantine facility if they re
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