Curious about how COVID-19 contact tracing is done?

Published by Biotech Connection Singapore on

By Sowjanya Kallakuri


Since the emergence of the very first COVID-19 case in Singapore, the government has worked actively to contain the spread of this highly transmissible illness. The country’s rapid development of COVID-19 test kits and extensive testing programme were internationally lauded at the start of the outbreak, but these actions would have done little to control the spread of disease without the accompanying process of contact tracing. Contact tracing plays a key role in limiting disease transmission early on in an infectious disease outbreak by identifying people who may have come in contact with an infected person, in order to quarantine them and break the chain of transmission. In addition, contact tracing provides clues as to how an infected person might have caught the virus, allowing authorities to identify hotspots or clusters and take appropriate measures to reduce the chance of future infections from these sources.


Tracing Workflow

The process initially begins in the hospital after a COVID-19 diagnosis is made. At the Singapore General Hospital (SGH), contact tracing is performed in teams of four that are on stand-by around the clock. These teams comprise healthcare workers that are SGH staff, working under the supervision and guidance of the hospital’s epidemiology team which collates and reviews the data, ascertains data integrity, and manages submissions or follow-ups, as necessary. There are 14 teams in total.

“As soon as there is laboratory confirmation of COVID-19, a contact tracing team is activated,” says Dr Indumathi Venkatachalam, an infectious disease consultant at SGH who supervises one of the teams, “they then have to report to the contact tracing center within 30 minutes or 1 hour depending on whether they are activated during or outside of office hours, respectively.” Typically, each team handles one to eight patients, depending on case load and complexity. The teams then contact the patient to gather information through an interview which is typically conducted over the telephone. Patients may receive the call when they are at home, whilst awaiting ambulance, if they were tested as an outpatient, or once they have been admitted to the hospital.

The interview process is exhaustive and helps patients connect the dots pertaining to their past events. Questions start off being fairly direct, such as ‘when did the symptoms start?’, which helps the team decide how far back into a patient’s history they should go to obtain relevant information. Since 14 days has been a widely used estimate of COVID-19’s incubation period, the team tries to gather as much data as possible on a patient’s activities up to a fortnight before the first day of symptoms. Asking about a patient’s routine is also common, as most people have a daily routine which helps in understanding the different places they have been to and the extent of possible exposure to the virus that causes COVID-19. Gradually, more indirect questions are introduced as contact tracers seek to fill the gaps in patients’ recollections. Under incredible time pressure, contact tracers must collect as many details as they can about a patient’s history and submit the information to the Ministry of Health (MOH) within approximately 2 hours of diagnosis.

Types of questions that contact tracers might ask
– What is your weekly routine?
– Did you do anything special in the preceding two weeks before symptom onset?
– What did you do once you started feeling unwell?
– Did you see a doctor and if so, which doctor did you see?
– Has anyone else around you been ill?
– What are your working hours?
– What do you do on weekends and weekdays evening after work?
– Who do you usually spend time with, or have meals with?
– Do you take public transport, and if so which bus or train do you take?
– What time and where do you usually board and alight?
– Do you take taxis, and if so do you have receipts or online confirmation for recent trips?
– Did you fly recently? If so, when and on which airline, and what was the seat number?
– Where are you staying now? If in a hotel, which hotel, and what is the room number?

To aid further processing, all of the information obtained from these initial interviews is entered into a standard template before submission to MOH, which then would further investigate and identify community contacts. This initial information gathered constitutes the activity mapping.  Backward mapping, which maps activities and contacts 14 days preceding symptom onset, is the process of identifying contacts from whom this patient could have acquired COVID-19. Forward mapping is performed to identify contacts to whom this patient might have inadvertently transmitted the virus to. These individuals, or primary contacts, will be obliged to undergo mandatory quarantine in an attempt to break the chain of transmission.


Forgetfulness and lack of cooperation are major challenges

As relatable as it sounds, patients may not remember relevant events when asked directly, and this is one of the challenges the contact tracing team faces. In this case, contact tracers might help patients by asking specific questions about whether there were any special events during the two-week period such as birthday celebrations or anniversaries. Alternatively, patients are asked to refer to recent photos, or their e-calendars, emails and messages to help remind them of their daily events. For taxi or rental car bookings, patients may be asked for receipts, and possibly credit card statements.

From time to time, a difficulty arises when a patient cannot be directly questioned. “Sadly, there are some occasions where the patients are too sick to talk,” says Dr Venkatachalam. In these cases, the team will contact their family or friends for collaborative history. There are also other ways of gathering information, for instance by looking at CCTV footage within the hospital premises to find out where patients have been.

In addition, some patients are unwilling to share names or contact numbers of individuals they have met. This usually happens with patients who do not trust that the teams are official contact tracers and are skeptical about sharing personal information with them. Given the detailed nature of questioning, this is a valid concern, but it presents major difficulties to the contact tracing team when patients do not cooperate, give misleading information, or are not forthcoming with information. Dr Venkatachalam says those who worry about providing personal data should be assured that the confidentiality of any information collected is strictly maintained. All electronic communication of patient information is conducted using password-protected standard templates and is used only for contact tracing purposes.

Finally, it can also be difficult if the patient has had multiple social interactions or travelled to crowded places, particularly if they used public transport during peak hours.


What you can do to help contact tracers do their job?

Knowing the nuts and bolts of contact tracing, what can we as individuals do to facilitate this process? Dr Venkatachalam suggests maintaining electronic records of transactions and significant events, such as details of any COVID-19 related symptoms. This can help increase the speed and accuracy of information collection should you need to provide any details as a patient or a primary contact. Being open to sharing your information once you have ascertained that the contact tracer is genuine (see this set of guidelines from MOH to identify scam calls) will also help, as well as downloading and using the Trace Together app which uses Bluetooth signals from mobile phones to determine and record users who have been within two meters of each other.

Nonetheless, contact tracing teams are still vital for conducting interviews and determining who counts as a close contact. Through identifying contacts and isolating people who could be transmitting the infection, we can hopefully stop the chain of transmission and protect our community.



We thank Dr Indumathi Venkatachalam and her team from SGH for their insightful comments and for the important work they do for this COVID-19 pandemic.



About the Author

Sowjanya is an Events Lead with BCS and a developmental geneticist by profession. She received her PhD from the German Cancer Research Centre, Heidelberg in Developmental Genetics. She is currently a research fellow at the Lee Kong Chian School of Medicine where she is studying the importance of hedgehog signalling in maintaining vessel integrity in Zebrafish. When not working, Sowjanya loves to travel, try out new cuisines and Zumba.




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