Developing a framework for assessing and managing individual-level risk of coronavirus disease 2019 (COVID-19) exposure in mobile populations

Purpose

Background

When outbreaks occur in areas with highly mobile populations and porous borders, the risk of further spread within an outbreak area or to other locations with a connection to an outbreak area (e.g., neighboring country, countries with flight connections) is high. The complex movement patterns in border communities and among mobile populations present challenges for identifying infected or exposed travelers and facilitating appropriate public health management strategies. Additionally, limitations in public health surveillance at points of entry contribute further challenges.¹

Recognizing that neighboring countries may be in different phases of the COVID-19 pandemic and have different strategies for preparedness and response, it is important that the comprehensive border health measures countries implement have “full respect for the dignity, human rights, and fundamental freedoms of persons” [International Health Regulations, Article 3]² while mitigating further international spread.

Objectives

The objectives of this framework are to:

• Describe methods to assess the individual-level risk of COVID-19 exposure and potential infection among mobile populations based on symptoms, travel, exposure, and diagnosis history
• Describe appropriate risk-mitigation strategies for mobile populations that are suitable for country resources
• Provide approaches to reduce risk of COVID-19 spread consistent with identified individual-level risk assessment results and associated risk-mitigation intervention levels

Methodology

This framework contains two parts. Part 1 addresses the first two objectives and Part 2 addresses the third objective.  Before initiating discussions related to Parts 1 and 2, ministries of health and their partners should gather information about the country’s legal framework, including legal authorities for isolation^* and quarantine^** of nationals and non-nationals, regional guidance and legal frameworks for border control measures, and available resources for public health interventions and communications.

Part 1

This framework describes methods to assign a risk-mitigation intervention level, e.g., none, minimal, intermediate, or high, based on an individual-level risk assessment. Topics in this part include applying information about existing symptoms consistent with COVID-19, travel history of being in an outbreak area with ongoing community transmission, exposure history to suspected or confirmed cases, and diagnosis history including test results.

Part 2

This framework features approaches to respond to the assigned risk-mitigation intervention level, considering country-level resources. Approaches are ordered in scale of least to most restrictive and include a range of approaches, including no intervention, self-monitoring, monitoring by the health authority, movement restrictions (including voluntary or mandatory quarantine at a residence or a government approved-location) for asymptomatic persons with known or potential exposure, to isolation (at a residence or in a healthcare facility) for symptomatic persons with suspected or confirmed infection. The selection of appropriate approaches in the framework should be guided by public health system capabilities and infrastructure and current outbreak status. Approaches outlined in this section may be incorporated into existing national-level guidance on contact tracing and monitoring of individuals who may have been exposed to COVID-19.

Limitations

Countries may not have established policies or regulatory authority to impose mandatory quarantine or isolation, and may have varying levels of resources to devote to monitoring or restricting movement of infected or exposed individuals across preparedness and response phases. This document does not recommend the same approaches for all countries and serves as a discussion guide to begin country-specific conversations. Ministry of health discussions will inform refinements to the approaches used for monitoring and movement restrictions of exposed persons and persons with suspected or confirmed infection throughout the pandemic.

^*Isolation is the separation of people known or suspected to be infected with a communicable disease and potentially infectious from those who are uninfected to prevent spread of the disease.

^**Quarantine is the separation of those known or suspected to be exposed to a communicable disease from those who are not exposed for the purpose of monitoring and to facilitate rapid isolation if they are identified as being infected.

Part 1: Assigning risk level based on individual-level risk assessment

• Lower risk
  • History of being in an area with no ongoing community transmission
  • Negative molecular (RT-PCR) or antigen test for SARS-CoV-2 (the virus that causes COVID-19) within a timeframe before departure defined by the receiving country or upon arrival³ and individual meets no other criteria in other risk categories
• Intermediate risk
  • History of being in an area with ongoing community transmission^**
    • Consideration: Individual risk level may vary if the individual fully practiced personal protective measures (e.g., social distancing; use of facemasks; handwashing; if traveler is a health care worker, use of recommended personal protective equipment during patient interactions)^4,5,6
  • History of attending a mass gathering or large social gathering such as a wedding
    • Consideration: Individual level risk level may vary if the individual and other participants fully practiced personal protective measures (e.g., social distancing; use of facemasks; handwashing)
  • Higher risk
    • A close contact⁷ of a person with confirmed COVID-19^,
      • Risk level can be further assessed by investigating whether the infected person and close contact consistently wore face masks or took other recommended precautions during exposure period
      • Additional factors to consider when defining close contact include proximity (closer distance likely increases exposure risk), duration of exposure (longer exposure time likely increases exposure risk), whether the infected individual was symptomatic (the period of onset of symptoms is associated with the highest level of viral shedding), if the infected person was likely to generate respirator aerosols (e.g. through coughing, singing, shouting), and other environmental factors (e.g. crowding, adequacy of ventilation, indoor or outdoor exposure)
    • Suspected or confirmed cases
      • Presence of signs and symptoms consistent with COVID-19 during travel or upon arrival
      • Positive RT-PCR or antigen test for SARS-CoV-2 before departure or upon arrival and not meeting criteria for discontinuation of isolation^8,9

^* Definitions of lower and higher risk activities in this document differ from CDC guidance for U.S. settings.¹⁰

^**WHO defines community transmission as: Countries/territories/areas experiencing large outbreaks of local transmission defined through an assessment of factors including, but not limited to: Large numbers of cases not linkable to transmission chains. Large number of cases from sentinel lab surveillance or increasing positive cases through sentinel samples, multiple unrelated clusters in several areas of the country/territory/area.¹¹ Refer to WHO (https://who.sprinklr.com/external icon) or national data for latest outbreak information and affected areas.