Effectiveness of Point of Entry Health Screening Measures among Travelers in the Detection and Containment of the International Spread of COVID-19: A Review of the Evidence

By inergency On Mar 28, 2024

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1. Introduction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a β-coronavirus, enveloped RNA virus, belonging to the Sarbecovirus subgenus and subfamily Orthocoronavirinae; SARS-CoV-2 causes coronavirus disease 2019 (COVID-19). It emerged in Wuhan China and spread throughout China and globally through human mobility. Bats are believed to be the natural host of SARS-CoV-2 while zoonotic transfer and spillover through mammals such as ferrets, pangolins and mink are thought to be potential intermediate hosts to infect humans [1,2,3,4]. The World Health Organization (WHO) declared COVID-19 a Public Health Emergency of International Concern (PHEIC) [1] on 30 January 2020.

Globally, as of 19 November 2023, the COVID-19 pandemic affected over 772 million people in 229 countries and territories with over 7 million deaths [5]. Although the WHO declared COVID-19 no longer a PHEIC on 5 May 2023, it continues to constitute a public health threat monitored and addressed at the country level [6]. The potential spread of the disease, and especially new variants, remains a challenge to public health surveillance systems [7]. The WHO was tracking three variants of interest (XBB.1.5, XBB.1.16 and EG.5) and seven variants under monitoring (BA.275, BA.286, CH.1.1, XBB, XBB.1.9.1, XBB.1.9.2 and XBB.2.3) as of 24 September 2023 [8].

Many studies have shown the potential of communicable diseases to spread from one country to another through airports, ports and ground crossings [9,10]. To help prevent this spread, countries are required under articles 19, 20 and 21 of WHO International Health Regulation of 2005 to develop core capacities at designated POEs for routine times and during emergencies. These requirements highlight the importance of POEs in mitigating the importation and exportation of infectious diseases. During the COVID-19 pandemic, enhanced health screenings at POEs were among the public health measures implemented to detect, delay or prevent further transmission of COVID-19 early on.

Enhanced public health screenings at POEs may include requiring travelers to fill out a risk assessment questionnaire either before or upon arrival or before departure, observing for signs and symptoms of communicable illness, measuring body temperature, or conducting rapid testing. With evolving COVID-19 epidemiology and transmission dynamics including emerging new variants and increased coverage of COVID-19 vaccination, the WHO recommended thorough, systematic and regular risk assessments to inform the introduction, adjustment and discontinuation of risk mitigation measures in the context of international travel [11]. This risk-based approach involved considering different factors such as local epidemiology in departure and destination countries, the volume of travelers between countries, existing bilateral and multilateral agreements between countries to facilitate free movement, the capacity to detect and care for cases and their contacts, public health and social measures implemented to control the spread of COVID-19 in departure and destination countries, and contextual factors such as the economic impact, human rights impact and feasibility of applying measures [11]. As the COVID-19 pandemic continued, countries adjusted their POE screening measures based on response experiences, WHO COVID-19 travel advices and the emergence of new scientific ways of addressing the epidemic.

Several studies found varying results after evaluating the effectiveness of POE screening measures in the detection and containment of communicable diseases [10,12]. Some studies found POE screening to be effective in delaying cross-border spread and others showed less effectiveness in detecting febrile travelers. Some infectious diseases with a long incubation period such as Ebola and the limited accuracy of temperature-measuring devices were among the factors hindering the effectiveness of POE screenings [13,14].

The present systematic review seeks to complement the existing body of knowledge on the effectiveness of entry and exit health screenings at POEs to detect and contain COVID-19. It analyzes the existing body of knowledge for updated screening guidelines, screening effectiveness and temperature-measuring devices used and the potential gaps for further studies.

2. Materials and Methods

2.1. Eligibility Criteria

This study followed the PICO framework whereby the eligible population was international travelers, and the intervention was entry and exit health screenings at POEs. The comparator was other interventions implemented outside the POE settings such as contact tracing, surveillance through Integrated Disease Surveillance and Response (IDSR), quarantine and health facility reporting. The outcomes included detection of COVID-19 among travelers at POEs and the delay and containment of COVID-19 transmission between countries. The systematic review protocol was prepared and published under PROSPERO guidelines (available online: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022336922, accessed on 8 June 2022).

2.2. Inclusion Criteria

The review included observational studies (cohort studies, case–control studies and cross-sectional), mathematical modeling and computational studies published worldwide in the English language in peer-reviewed journals and the gray literature between 2019 and 2022. These studies had to include an analysis of entry or exit screening practices at international airports, ports or ground crossings.

2.3. Exclusion Criteria

All reviews, editorials, full-text papers that were not available, studies involving migrant/asylum seekers and responses to COVID-19 in a particular conveyance which was part of the national response were excluded from the list. Publications reporting screening of other infectious diseases apart from COVID-19 such as TB, HIV and hepatitis were excluded.

2.4. Data Sources

The systematic search accessed many international databases for primary data sources including Scopus, PubMed, Web of Science, Global Health, CINAHL and Embase. Additional resources were gathered from Google Scholar and the gray literature was added from international organizations such as the WHO’s Institutional Repository for Information Sharing, the International Civil Aviation Organization (ICAO), International Maritime Organization (IMO), East Africa Community (EAC), Southern African Development Community (SADC) and Common Market for Eastern and Southern Africa (COMESA). The search of references of included studies was conducted and included in the study if criteria were met.

2.5. Search Strategy

2.5.1. Search Topics and Definitions

This review covers the following key topics:

(a): Points of Entry: as defined under the IHR, 2005, as a passage for international entry or exit of travelers, baggage, cargo, containers, conveyances, goods and postal parcels as well as agencies and areas providing services to them on entry or exit;
(b): Entry health screening: public health measures (such as temperature screening, visual inspection for signs of illness, exposure and travel history assessment and testing) implemented at POEs upon arrival with the purpose of identifying travelers infected with or exposed to COVID-19 to mitigate importation of COVID-19;
(c): Exit health screening: public health measures (such as temperature screening, visual inspection for signs of illness, exposure and travel history assessment and testing) implemented at POEs before departure with the purpose of identifying travelers infected or exposed to COVID-19 to prevent exportation of COVID-19 to other countries;
(d): COVID-19 detection: confirmation of SARS-CoV-2 virus through accepted methods;
(e): Travelers: passengers and crew under international voyage.

2.5.2. Search Terms

The search terms were obtained through defining the synonyms of the terms, truncating and referencing from other similar published reviews. Table 1 below summarizes the terms used.

2.6. Data Extraction (Selection and Coding)

Studies were included if they evaluated health screening measures at POEs such as performance of fever screening devices, signs, symptom and exposure assessments, and rapid antigen test use among international travelers. These citations were exported to Rayyan (Rayyan System Inc, Cambridge, MA, USA) to screen based on the title and abstracts and to remove duplication. Rayyan is a free web and mobile app (http://rayyan.qcri.org, accessed on 20 June 2022) that expedites initial screenings. The software has been evaluated and found to be among the suitable tools for abstract and title screening [15,16]. Out of 33,744 documents retrieved, 109 were duplicates, which after removal, left a total of 33,635 subjected to level 1 screening. The title and abstract review excluded 33,199 documents, leaving 436 for full-text screening (level 2), based on the inclusion and exclusion criteria. Thirty-eight documents remained after the level 2 review. Searching the references of included studies led to including five more studies, making a total of 43 documents eligible for data extraction. Three independent reviewers (RK, EGK and EM) completed data extraction by using the data extraction protocol. Any disagreement among reviewers was resolved by discussion to reach consensus.

2.7. Quality of Included Articles

The quality of the included articles was assessed based on meeting the inclusion criteria.

2.8. Data Synthesis

All identified eligible studies were included in the synthesis. The review results were presented in Excel format, with columns representing the title of the article, author, year of publication, country where the study was conducted, screening strategy used, study design, objective, methodology, key findings, relevance, number of travelers screened, number of travelers found with COVID-19, type of POE (airport, port and ground crossing), performance of screening devices and synthesis of recommendations from an international organization. Health screening in this case refers to either symptom screening using risk assessment questionnaires, fever screening using infrared thermal scanners or illness screening using rapid antigen tests for COVID-19. The effectiveness of POE screening was assessed on the ability of these measures to detect COVID-19 cases, delay the onset of the COVID-19 epidemic and reduce transmission. After extracting data, the reviewers decided that a meta-analysis was not possible due to the nature of the data obtained. Research articles were heterogeneous and did not include all the information required including test statistics to enable meta-analysis.

4. Discussion

This systematic review collated data on the effectiveness of POE-based health screening measures in the detection and containment of the international spread of COVID-19. The scientific literature included in this review exhibited considerable heterogeneity, encompassing various study designs, units of observation and computational studies. Despite this variability, the findings presented contentious perspectives on the effectiveness of POE health screening. Several included studies reported that POE health screening measures demonstrated efficacy in detecting significant COVID-19 cases, including variants of concern [17,21,22,24,25,26,27,28,29,30,32,35,37,38,39,40]. Additionally, these measures were associated with a delay in the onset of the epidemic [42,43,44,45] and reduction in transmission risk [45,46,48,49,50]. Notably, the methodologies employed in different countries exhibited considerable diversity, involving a range of screening methods such as testing [18,19,20,21,22,23,24,25,26,27,28,29,30,31]; sign and symptom assessment [20,21,27,28,30,31,32,33,34,35]; body temperature measurement [20,24,31,33,34,35,36]; exposure assessment [20,21,27,30,32,35]; daily telephone calls of travelers after arrival for 14 days [37]; checking vaccination status [22]; and inspection of RT-PCR test certificates [27].

Additionally, this review highlighted a crucial aspect of POE health screenings predicted to delay the onset of outbreak of COVID-19 by between 8 and 32.5 days depending on the sensitivity, reproductive number and screening method employed [42,43,44,47]. Further, this review predicted the reduction in COVID-19 transmission risk during traveling by 30–35% through symptom screening and immediate isolation and reduction in exportation risk by 44–72% through the testing of all asymptomatic travelers during exit screening [45].

Specifically focusing on molecular tests, including rapid tests and RT-PCR as screening measures at POEs, this review indicated a high detection level, ranging from 94% to 99.6%, especially when combined with isolation and quarantine [37,38,40,46,51]. Observational studies also contributed valuable insights, revealing that POE screening detected between 6% and 77.9% of COVID-19 cases [17,18,19,21,27]. Recent instances, such as the detection of the Omicron B.1.1, a variant of concern (VOC), in Venezuela at a Maiquetia airport [23] and the identification of COVID-19 lineages in Japan at four airport quarantine stations [26], underscore the practical significance of molecular testing at POEs. Predictive models from selected studies, like the one by Quilty, Clifford [37], emphasized the effectiveness of syndromic exit screening, though acknowledging potential missed cases. Similarly, some selected observational studies found sign and symptom screening combined with thermal screening detecting between 2% and 57.8% [24,30,31,32].

Comparative effectiveness analyses suggested that POE screening outperformed other interventions such as contact tracing, Integrated Disease Surveillance and Response, quarantine and health facility reporting [20,59]. Notably, international organizations have continually published guidelines, recommending a risk-based approach over universal testing for all travelers [11,53,54,57]. COVID-19 vaccination was not a recommended mandatory requirement by the WHO for both entry and exit based on vaccination distribution inequalities among member states [54].

The findings summarized in this review underscore the crucial role of POE health screening in the early detection, delay and containment of the COVID-19 pandemic. Maximum benefit is derived when screening measures involve a combination of sign and symptom screening, temperature screening, testing and, when feasible, quarantine of exposed travelers. The considerable variation in detection levels may be attributed to differences in the sensitivity and specificity of screening devices, evolving border health policies and changing disease transmission dynamics.

These findings are consistent with other studies, including reviews. A similar review conducted to assess the travel-related control measures to contain the COVID-19 pandemic found health screening to be capable of delaying COVID-19 by between 1 and 183 days and capable of detecting the disease in between 10% and 53% [60]. Similarly, another review indicated that POE-based measures detected only half of the cases [10]. Other reviews indicated that thermal screening using non-contact thermal meters was ineffective in limiting the spread of the COVID-19 pandemic [37,61], similar to what was found in this study. This review found better detection when screening strategies involved a combination of testing, similar to the results of other review articles [60]. Furthermore, Gunaratnam, Tobin [62] found that during the 2009 H1N1 influenza pandemic, 5845 travelers screened at Sydney International Airport, New South Wales, Australia, were identified as febrile out of 625,147 total screened during that period. Three travelers were confirmed with H1N1 (detection rate of 0.05 per 10,000 screened). The author estimated that during the same period, 45 cases of H1N1 passed through that airport, thus estimating the sensitivity values to be 6.67%.

The present review found POE screening more effective than other interventions in preventing the importation of COVID-19 cases, similar to another study by Zhang, Yang [63], who found POE screening to be the second most effective intervention in detecting imported cases of H1N1 compared to influenza-like illness screening in hospitals, medical follow-up of travelers from overseas and quarantined close contacts. On the contrary, in Australia, most H1N1 cases were detected in emergency departments [62]. The variation in screening performance observed in this review may be due to a lack of uniformity in the application of screening strategies as well as screening capacity-related challenges. In India, at Jaipur International Airport, Neha, Joshi [64] reported poor cooperation among passengers, masking symptoms, apprehension and inadequate human resources as barriers to POE screening effectiveness. Similarly, other studies have reported inadequate personal protective equipment and supplies, insufficient screening infrastructure, inadequately trained staff and the existence of many informal entry points, lack of training among staff, missing information in health alert cards, lack of harmonized traveler screening measures, poor intersectoral coordination, lack of transport, absence of an public health emergency plan, and inadequate financial resources as potential challenges affecting POE health screening [65,66,67,68].

The main limitation of this study is that many included papers reported POE screening for airports and ground crossings with limited studies for ports. The reported findings might have underreported what is being implemented at ports. Also, it is impossible to know how many travelers had transmissible COVID-19 during their travel through a POE and thus, it was difficult to judge whether they missed the cases or they detected the actual number. Further, risk of importation and exportation of COVID-19 varied throughout the pandemic based on a variety of border health policies implemented around the world which impacted screening measures and when, where and how individuals were traveling. Moreover, future reviews should consider conducting a meta-analysis which was not performed due to heterogeneousness of the studies obtained.

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