Contact tracing – a weapon to combat Covid-19 transmission

Content image - Phnom Penh Post
Some countries have adopted a SIM-card-based location tracking app. This method poses challenges in health surveillance and epidemiology, but several experts say this should work upon the patients’ consent. AFP

In a pandemic or outbreak, contact tracing is the key to preventing transmission through quarantine. Not only will contact tracing ensure efficient testing and early treatment before a prognostic worsens, it will also provide reliable data in modelling to predict the spread of a disease.

Contact tracing is exercised through surveillance by a team of surveillants, tracers or epidemiologists. Each local administration’s Covid-19 task force has its surveillance team, whose job is akin to a call centre. Their daily duty is to call every Covid-19 patient and their close contacts. The central task force, laboratories or referral hospitals that treat Covid-19 patients can also send a contact list of patients to the surveillance or contact tracer team. The surveillants will phone those patients. The first question will be: “Who have you seen in the last 14 days?” or, “Who do you live with?” The question is a method to trace virus transmission.

However, there are several problems regarding the stigma facing infected people. Usually, the interviewee will resist and reply: “Who are you?” or, “Can I have your official assignment letter?” In some cases they will deny they are infected, saying: “Sorry, I’m not sick. You dialed the wrong number.”

A cooperative patient will answer the questions clearly. However, another problem arises – the method for asking a patient to sift through their memories is susceptible to error. In epidemiology, this is prone to causing bias, which is called recall bias. A surveillant who does not get the desired information usually leaves the form blank or guesses using their opinion. When that happens, the contact tracing will result in data inaccuracy.

Problematic data may also exist because of the long-form questionnaires contact tracers and surveillants have to deal with. Imagine, for example, in Greater Jakarta, a surveillant must phone around 100 people every day, with each interview lasting about 20 to 30 minutes. In fact, a regional task force, which commonly hires 10 surveillants, is unable to complete the job in a couple of days as required.

Contact tracers or surveillants also deal with many data systems that are unintegrated. This will complicate the process of inputting a large amount of data. The incomplete data is used in the analysis or effective reproduction number (modelling in analysing the spread of the virus after intervention), by the task force. The result usually suggests that the disease is under control, even though the truth is the opposite. This is referred to as an “overestimation”.

Data problems may also mislead the task force when identifying Covid-19 transmission clusters. Even surveillants assigned in cities that are considered a benchmark in handling the pandemic also face these problems. Contact tracing in such cities has never reached 80 per cent of the set target.

There are two options to address these problems. First and foremost, develop a technology for tracing or tracking. The national Covid-19 task force and the Health Ministry have been aware of this need from the beginning. They have been applying many data systems in surveillance, the most recent being an app called Silacak. The new app was designed to ensure the effectiveness of contact tracing.

However, recall bias and data integration remain the obstacles. Some countries have adopted a SIM-card-based location tracking app. The challenge for this method is potential infringement of the privacy of patients. This method poses challenges in health surveillance and epidemiology, but several experts say this should work upon the patients’ consent. In Indonesia, at the beginning of the pandemic, this kind of app was launched by the Communications and Information Ministry and required approval of the users. However, the national Covid-19 task force and the Health Ministry have not done enough to promote it.

Second, we must consider how to optimise contact tracing at the grassroots and increase community participation. The tracers’ phone calls should not be perceived as a threat by citizens. The government has to double efforts to convince the public about the importance of tracing to stop Covid-19 transmission and eradicate the stigma.

Our attention should also go to rural areas and indigenous communities, where internet and electricity is lacking or absent. The Communications and Information Ministry reported last year that 24,000 villages had no access to the internet. Those areas need a participatory model for contact tracing named Community Based Surveillance, which works in rural Africa. This approach requires involvement of volunteers from local communities. We hope the government prioritises contact tracing and surveillance to lower transmission and reduce the mortality rate of Covid-19.

Masdalina Pane is a Health Ministry researcher for communicable diseases and vaccines and a consultant for Centres for Disease Control and Prevention-The Indonesian Epidemiology Association (CDC-PAEI), Covid-19 Regional Empowerment in Indonesia. Dhihram Tenrisau is a former Depok Covid-19 task force contact tracer.