This document is part of a series of discussion notes addressing fundamental questions about the COVID-19 crisis and response strategies. These documents are based on the best scientific information available and may be updated as new information comes to light.
This publication is written by Anna Llupià (Hospital Clínic de Barcelona), Maria Tusell, Júlia Montañà, Alberto García-Basteiro y Caterina Guinovart (ISGlobal). The text adresses how to improve the case and contact tracing during the COVID-19 pandemic.
“Testing, isolation and contact tracing” are “the backbone of the response” to the COVID-19 epidemic, according to the World Health Organisation (WHO). Most of the countries that managed to avoid a steep epidemic curve (South Korea, Singapore, China, Albania, New Zealand, etc.) did so by starting contact tracing early in the outbreak.
Characteristics of COVID-19 to Consider in Case Monitoring and Contact Tracing
- Short incubation period (1-14 days): Contacts must be identified quickly to stop them from infecting other people.
- People without symptoms can spread the disease: Contact tracing is necessary in asymptomatic cases.
- Transmission can occur up to 48 hours before the onset of symptoms: Close contacts of the infected person during that period must be identified.
- High transmissibility + large volume of cases and contacts: Contact tracing systems must be flexible and adequately resourced (staff and technology).
- Viral spread will continue until an effective vaccine is developed, so new waves of infection and pressure on the health care system are likely: Surveillance and contact tracing will have to continue for some time, even after the last local case is reported.
Case Identification: Automated Information Systems for Fast and Exhaustive Reporting
Each country has its own surveillance system responsible for managing cases of notifiable diseases, including COVID-19. Surveillance systems typically rely on case reports from health care facilities and diagnostic testing laboratories to identify (and, if required, isolate) cases and detect outbreaks and epidemics.
In Spain, notification is not always done via electronic health information systems. In other words, the cases recorded in a health information system are not automatically sent to the surveillance network; manual (non-automated) reporting must be done in parallel. Consequently, when the number of cases increases, reporting may be delayed.
In the case of COVID-19, prompt reporting is essential. Any delay in reporting can lead to delays in contact tracing, which in turn allows contacts to spread the disease before they can be isolated.
Notifiable disease reporting has been practised for decades, but the COVID-19 epidemic presents an opportunity to strengthen and improve the system. Advances in health information systems, including electronic health records, make it possible to standardise the reporting of cases of COVID-19 (and, ideally, other notifiable diseases). Under a standardised reporting system, cases are automatically reported as soon as the patient comes into contact with the health system. Standardised reporting also helps surveillance systems to operate more smoothly, ensuring fast and exhaustive identification of cases.
All confirmed cases of COVID-19 should be reported and isolated. Probable cases (patients diagnosed on the basis of symptoms and radiology) and suspected cases (patients diagnosed on the basis of symptoms only) should also be reported and isolated if diagnostic testing is not an option for whatever reason. Contact tracing should begin immediately when a case has been identified and the patient isolated
Contact Identification: Bluetooth and Geolocation Technologies Are No Substitute for Traditional Contact Tracing
The first step in contact tracing is to identify people who have been in close contact with the infected person any time after 48 hours before the onset of symptoms (or, in the case of asymptomatic cases, any time after 48 hours before the diagnostic test was performed). Anyone who has been less than 2 metres away from the infected person for 15 minutes or more is considered a close contact. In addition, anyone who has shared a closed environment with the infected person—e.g. a home, a meeting room, or an aircraft (within two seats in any direction)—for 15 minutes or more is also considered a close contact.
It is important to identify contacts as quickly as possible so that they can go into quarantine immediately and avoid infecting other people.
Active monitoring of contacts throughout the 14-day period increases adherence to quarantine. Monitoring can take the form of a daily telephone call from a contact tracer. It can also be semi-automated: daily text messages asking the contact to record their temperature and symptoms via an online questionnaire or notifications from a mobile application (app) that the contact can use to provide this information.
Technologies could be useful as a complement to traditional contact tracing, but they should not be relied on exclusively. New technologies make it possible to identify all of the infected person’s close contacts—both known and unknown—thereby increasing the reach and impact of contact tracing.
However, these technologies also have many limitations. First, it is not always possible to reliably calculate the distances between people (or, for example, to determine whether or not there was a wall between them). Second, the use of these tools may have legal implications, particularly with regard to data protection. Finally, these technologies are more useful when used by a large number of people, which requires a high level of public acceptance. If all data were anonymised, it would be easier to gain public acceptance and comply with regulations, but it would be impossible to confirrm that the contacts identifed by mobile technology were in fact close contacts of known cases.
Resources Needed for Contact Tracing
In order for contact tracing to be carried out in all confirmed and suspected cases, surveillance services must be assigned additional full-time staff and technical resources so that assistance can be provided and surveillance can be carried out even when the virus is spreading rapidly. The system needs to be flexible and capable of increasing and decreasing its staff according to needs in different phases of the epidemic.
Requirements for an Efficient Surveillance and Contact Tracing System
In conclusion, the requirements for an efficient surveillance and contact tracing system that minimises the amount of manual work are as follows:
- Early and exhaustive case detection. It is important to detect cases as early as possible by testing all symptomatic individuals. If diagnostic tests are in short supply, anyone who develops symptoms should be considered a possible case and self-reporting of symptoms should be encouraged.
- Reporting of cases in (almost) real time. It is essential to minimise the time between the identification of a case and the start of contact tracing. Rapid reporting of suspected, probable and confirmed cases—ideally via existing health information systems—can help to achieve this goal. It is also necessary to identify and eliminate duplicates entering the system by different routes (e.g. detection in primary care and by laboratory testing).
- Planning of human and technical resources for the contact tracing system, with the flexibility to add more staff as case volume increases.
- Rapid identification and quarantining of contacts, supported by online surveys. The use of online surveys to identify contacts plays a critical role in expediting the process. The data collected are subsequently confirmed by the contact tracing team.
- Semi-automated active monitoring of contacts. Automated communications via text message, email or mobile app (where possible) can speed up the process and drastically reduce the number of telephone calls.
- Centralised dashboard to coordinate the teams responsible for different tasks (case interviews, follow-up with contacts, etc.).
- Visualisation of transmission chains and control panel. By mapping the links between known cases and their contacts and identifying the date and place of contact, it is possible to represent transmission chains visually and detect “hotspots” where numerous contacts occur.
- Resources to facilitate isolation and quarantine. To ensure that cases and contacts are able to go into isolation or quarantine, it may be necessary to provide relocation assistance, financial support and welfare aid.
- Inclusive communication campaigns that incorporate the citizen’s perspective, build public trust and clarify the key concepts of contact tracing.