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Contact Tracing during Covid Times

Contact tracing aims to identify the people who have been in close proximity to a person who has tested positive.

Testing is quickly becoming a statistic of national pride. Countries are clamoring to test more and more people and increase accessibility for the population to receive testing. We will cover testing, its aims, and its future in a separate blog. Testing people is only half the story. It gives us information on who is infected, but to minimize the spread of infection other measures must be introduced alongside it. Contact tracing is one of these measures.



Most people who fall ill or test positive for COVID can spread the virus 2-3 days before getting the first symptoms. They can unintentionally infect the people they meet in public or work with. If infected, these people can also spread the infection without knowing it, and this leads to a rapid spread of COVID in the community, as we saw at the start of this pandemic.

Lockdown has been very good at reducing R0 (rate of infection spread), but this is done crudely by physically keeping people separated in their own homes. As R0 reduces and lockdown restrictions ease, this will no longer be feasible. By aggressively testing the population we can identify people who may be infected and instruct them and their household to remain in lockdown.

Contact tracing aims to identify the people who have been in close proximity to a person who has tested positive. This is traditionally done by questioning the infected person about their recent travel, people they met, where they work, and so on. These contacts are then instructed to isolate as well and can be tested to confirm infection. By preventing these potentially infected patients from spreading the infection, the R0 decreases and the second peak in infections is prevented.

This is not a new concept and is used often for communicable diseases such as tuberculosis or sexually transmitted infections. It has also been used in previous pandemics including 2003 SARS outbreak. In 2014 Liberia experienced one of the largest contact tracing efforts in history, with 25,000 people identified annually. Similarly in the US 29,000 people were monitored by state and local health departments after returning from West Africa, and this laid the groundwork for future COVID-19 contact tracing efforts.

The WHO has laid out guidelines for identifying potential contacts, including:

  • Being within 1 metre of a COVID-19 case for >15 minutes;
  • Direct physical contact with a COVID-19 case; 
  • Providing direct care for patients with COVID-19 disease without using proper personal protective equipment (PPE);



Today countries have updated their methodology for contact tracing, utilizing technology and smartphones to increase the accuracy and volume of data available to public health officials.

South Korea had contact tracing plans in place due to the MERS epidemic in 2015, and this was built upon for COVID. Contact tracing utilizes smartphone GPS data, credit card transaction records, and surveillance camera footage. At Seoul’s Incheon International Airport, there are walkthrough facilities to test people with symptoms of COVID and follow up those without symptoms in 3 days. New arrivals also have to download a government smartphone app to track their location and provide info on symptoms.

Singapore’s mobile app also utilizes Bluetooth data to determine devices that have been in close proximity to the infected persons’ phone and tracking these devices can identify potential contacts. It has over 1.1 million users, just under one-fifth of the country’s population.

Apple and Google together own almost the entire mobile operating system market with their respective iOS and Android platforms. They have worked together to create a framework that can allow governments to efficiently create and utilize contact tracing apps. Their efforts use Bluetooth Low Energy beacons. Nearby devices that wirelessly “shake hands” create randomly generated codes without any user-identifiable details (name, location etc). Based off Bluetooth data it can provide an estimate on distance and length of contact.  If one of the devices is identified as belonging to an infected person, all devices that have been in close proximity are alerted.



There are limitations present, both with the methodology used and with contact tracing itself. For one, it is quite a laborious and expensive process, and works well when there are low levels of infection in the community. During pandemics, it can quickly overwhelm the contact tracing departments if they are not adequately prepared and provide excessive information that cannot be utilized effectively. It is also not useful during a lockdown, as the lockdown itself artificially lowers infectivity. Instead, it must be implemented once the peak has passed.

Effective contact tracing is also expensive and labor-intensive. The state of Massachusetts has budgeted $44 million for its contact tracing program with 2,000 tracers. If implemented nationally it would cost the US an estimated $3.6 billion and require as many as 300,000 tracers. For app-based contact tracing to work around 80% of the population needs to have the app installed, and we have seen even small countries like Singapore struggle to push past 20%.

Finally, a major issue is a privacy. Poorly coded apps with little transparency can fail to anonymize vital personally identifiable data. This may be accessed by third parties or sold on to others, putting the privacy of millions of people at risk. There are also concerns by privacy watchdogs on the unfettered access by governments to this data, and whether this can be used in an oppressive manor.


If implemented correctly contact tracing has the potential to have a significant impact on reducing infectivity and allowing states and countries to open up their economies quickly and safely. Of course, this depends on the widespread use of contact tracing, and people abiding by government suggestions. Sadly, in the news, it is now too common to see resistance to basic measures such as use of masks in public, so we will have to see whether contact tracing will have any better success.


Dr Rajan Choudhary, UK, Chief Product Officer, Second Medic Inc