In the post-COVID-19 era, What should we do at points of entry?

07/03/2022
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The coronavirus disease 2019 (COVID-19) pandemic has imposed an enormous disease burden worldwide, and the Delta variant now has become dominant in 53 countries. On July 21, 2021, a small superspreader event occurred at Lukou International Airport in Nanjing, China. During a routine nucleic acid amplification test (NAAT) conducted on airport staff, nine returned positive results , all of which were infected with the Delta variant. In the days that followed, the chain of transmission continued to extend, forming a chain of intracity and inter-provincial transmission, linking twenty-two cities in eight provinces in China.
In the context of emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, increasing the number of tests during the quarantine period, shortening the regular testing period for staff with a high risk of exposure at airports, and identifying COVID-19 patients as early as possible through rapid screening may aid the control of the epidemic at border entry.
The current standard for detection of SARS-CoV-2 is reverse transcriptase polymerase chain reaction (RT-PCR) tests, which has high accuracy, but it has high requirements for testing equipment and operators, and is expensive and time-consuming (most would take 1–3 days). During the waiting time for the test results, infections can spread, and this is particularly troublesome for border entry management. On the other hand, rapid antigen tests (RAT) most only take 15–30 min to obtain test results and are simple and inexpensive. If the viral load in the sample is low, the test can be negative. The pooled sensitivity and pooled specificity of Standard Q COVID-19 Ag test, a RAT in the emergency use listing that was recommended by the WHO, were 0.83 (95% CI 0.63–0.94) and 0.99 (95%CI, 0.95–1.00), respectively.
Considering that RAT is faster than RT-PCR, and they yield similar results during periods of high viral load, we believe that the use of RT-PCR combined with RAT at border entry can better identify individuals with contagious levels of viral load, which is also of great help at points of entry for rapid triage and management of suspected populations at an early stage.
We recommend RT-PCR combined with RAT at points of entry: (1) RAT can be added to the detection phase at ports of entry to detect asymptomatic infections as early as possible; (2) RAT can be added to post-entry quarantine every three days or less to reduce the rate of missed detection in later quarantine; (3) Adding regular RAT to regular PCR testing for key airport personnel to prevent cross-infection and conduct closed-off management. In the face of sporadic Delta variant outbreaks, the combination of the two could help rapid triage and management of suspected populations at an early stage and thus contain the outbreak more quickly and effectively.

FIG.1  The recommended detection process at Points of Entry.


(+): the results of detection are positive, (−): the results of detection are negative, RAT+NAAT Rapid Antigen Test combined with nucleic acid detection


REFERENCE
Zhiqing Zhan, Jie Li, Zhangkai J, Cheng. Rapid Antigen Test Combine with Nucleic Acid Detection: A Better Strategy for COVID‑19 Screening at Points of Entry. Journal of Epidemiology and Global Health