| 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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