THE TAKE AWAY: The effect of travel restrictions on the coronavirus outbreak

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This is only a bullet point summary of a longer and more in-depth Science paper, “The effect of travel restrictions on the spread of the 2019 novel coronavirus (COVID-19) outbreak”. We suggest reading the paper in full on the publisher’s website for a better understanding of the points made here.

NOTE: Quarantine of Wuhan was implemented on 23 January, 2020.

  • On 22 January 2020, the projected median number of cases with no travel restrictions for Mainland China excluding Wuhan is 7,474 [90% CI 3,529-16,142]. The overwhelming majority of cases are in Wuhan with a median number of 117,584 [90% CI 62,468-199,581].
  • The overall reduction of cases in Mainland China excluding Wuhan is close to 10% by 31 January 2020, with a relative reduction of cases across specific locations varying in a range from 1% to 58%
  • The model indicates clearly that as of 23 January 2020, the epidemic was seeded in several locations across Mainland China.
  • The modeling results suggest that in Mainland China only one out of four cases are detected and confirmed.
  • The model indicates that after the travel restrictions in Wuhan are implemented on 23 January, the top 5 ranked cities as the origin of international case importations are Shanghai, Beijing, Shenzhen, Guangzhou, and Kunming.
  • In terms of relative risk of importation, the countries at higher risk of importation after the implementation of the Wuhan travel ban are: Japan (11% pre-travel ban, 13.9% post-travel ban), Thailand (22.8% pre-travel ban, 13% post-travel ban), Republic of Korea (7.4% pre-travel ban, 11.3% post-travel ban), Taiwan (9.5% pre-travel ban, 10% post-travel ban), and USA (4.7% pre-travel ban, 5.7% post-travel ban).
  • The concurrent presence of both travel and transmissibility reductions, however, produce a much larger synergistic effect visible by both delaying the epidemic activity in Mainland China and the number of internationally imported cases.
  • The strong transmissibility reduction (r = 0.5) along with travel restrictions does delay the epidemic growth in Mainland China that never surpasses the daily incidence of 1 case per 1,000 in Mainland China, and the number of imported cases at international destinations are always in the single digit range.
  • It is worth remarking that a large number of imported infected individuals from Mainland China were undetected and have been potentially dispersed to international locations.
  • By 1 February 2020 in the strong transmissibility reduction scenario the model estimates 101 [90% CI 50-173] importation events with one or more potential cases that could be seeding multiple epidemic outbreaks across the world, thus potentially leading to the international expansion of the COVID-19 epidemic.
  • The model indicates that while the Wuhan travel ban was initially effective at reducing international case importations, the number of cases observed outside Mainland China will resume its growth after 2-3 weeks from cases that originated elsewhere.
  • Furthermore, the modeling study shows that additional travel limitations up to 90% of the traffic have a modest effect unless paired with public health interventions and behavioral changes that achieve a considerable reduction in the disease transmissibility.
  • The model also indicates that even in the presence of the strong travel restrictions in place to and from Mainland China since 23 January 2020, a large number of individuals exposed to the SARS-CoV-2 have been traveling internationally without being detected.

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Read the paper in full here.

IMAGE SOURCE: Creative Commons

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