Buzz
Contact tracing is an indispensable method for controlling the spread of infectious diseases. In the case of COVID-19, it is a fundamental component of strategies such as the World Health Organization’s guidelines for easing distancing restrictions. But what exactly is contact tracing, and how is it implemented?
Contact tracing identifies individuals at higher risk of infection
When one person falls ill, it’s probable they’ve transmitted the disease to others. Contact tracing, a cornerstone of epidemiology, helps locate these individuals. This straightforward, often low-tech process involves interviewing people to determine who the infected individual interacted with.
Contagion, a film that remains strikingly relevant today, includes several scenes depicting a dramatized approach to contact tracing. Kate Winslet’s character interrogates a deceased patient’s colleagues and partner to uncover who she interacted with in the days leading up to her death.
A contact tracing protocol for COVID-19 cases is available here (provided by the nonprofit Vital Strategies, which the CDC references on their COVID-19 contact tracing page).
As outlined in this draft protocol, once an individual is confirmed as a positive case, they should be interviewed to pinpoint when they were most likely contagious. The interviewer must then compile a list of individuals who may have been exposed, based on the following criteria:
Contacts from 48 hours before symptoms appeared until the start of isolation or up to 7 days after symptom onset and 72 hours after fever subsides:
1. Household members
2. Intimate partners
3. Caregivers within the household
4. Individuals who have had close contact (starting with a 30-minute threshold)
Following this, the contact tracer would reach out to these individuals to inform them of their potential exposure. Ideally, this notification would remain anonymous, safeguarding the privacy of the infected person’s medical details. The tracer would then monitor these contacts over time to determine if they develop symptoms. If they do, the process would repeat for their contacts as well.
If the infected individual attended large gatherings while contagious, others present at those events might also need to be notified. Contact tracing not only identifies those who are ill but also ensures that exposed individuals are aware of their risk. This allows them to self-quarantine and monitor for symptoms, playing a crucial role in breaking the chain of transmission.
This task is enormous in scale and complexity.
Contact tracing, while not technologically advanced, demands significant manpower. Health departments aim to curb outbreaks early by tracking a small number of contacts, hoping to contain the spread swiftly.
In the case of COVID-19, with its vast number of cases, scaling contact tracing is essential. Both the CDC and WHO have dedicated teams for this purpose, yet their capacity is limited.
China has implemented a large-scale tracking system via an app. This tool integrates a person’s ID, phone number, and health status, assigning color codes: green for healthy, red for quarantine, and yellow for potential exposure.
However, skepticism remains about the efficacy of app-based contact tracing. Can phones accurately identify infectious contacts, or do they merely approximate locations? Privacy issues also arise: Who controls the data? How is it used? What if someone opts out? While this modern approach differs from traditional methods, its full implications are still unclear.
