The five hallmarks of successful contact tracing during the coronavirus pandemic
Contact tracing is the process of finding, assessing and managing the people who have been exposed to a disease, according to the World Health Organization (WHO).
We do it to prevent more people from getting sick with the same disease.
This is what’s made it such an important public health tool for controlling COVID-19.
It may be a crucial process and one that public health teams have been using for a long time — but it’s also quite a hard one to get right.
So what does contact tracing actually involve and why is it so difficult?
We spoke to University of New South Wales (UNSW) Professors Mary-Louise McLaws and Raina MacIntyre — who both specialise in infectious diseases and epidemiology — to give us the lowdown on the hallmarks of successful contact tracing.
1. Detection and investigation
To find coronavirus cases, you’ve got to be able to detect them in the first place, Professor McLaws says.
And to be able to do that, surveillance is needed.
“You need to contact everybody before they’ve had time to become sources of infection to everybody else,” she explains.
“So, you’ve got to find them before day four or five, because most people wait for two to three days before they’re tested.”
Professor McLaws and Professor MacIntyre both say a good indicator of an active and competent contact tracing system is a contact tracer getting in touch with the positive case they’re trying to nail down within 24 hours of their diagnosis.
“One of our approaches in Australia is doing contact tracing in the first 24 hours of receiving a diagnosis, and I believe that Victoria is at 100 per cent at the moment,” says Professor McLaws.
“That number was lower recently, because of such a high caseload.”
Imagine a contact tracer hasn’t been able to make contact with a confirmed case until five days after they were diagnosed.
“Now, they’ve potentially infected others, who now have had time to get into that ‘serial interval’, which is day three, four and five after exposure before they become silent sources of infection because they haven’t developed symptoms yet.”
This is why the epidemiologist says the next hallmark is crucial.
3. Number of tracers
It’s easy to see how contact tracing would have been difficult in Victoria when the state’s case numbers were at their height during the state’s second lockdown, according to Professor McLaws.
“If they could keep up with that amount within 24 hours I’d be very, very surprised,” she says.
“Based on how I saw the numbers going up, so high and so rapidly, I assumed they weren’t keeping up with the caseload.
“Victoria was in the green and amber zone since March and then they got in the amber zone for a while, but then on June 18 they went red and they just consistently went red.”
The epidemiologist says the reason this happened is that the state did not have enough trained contact tracers to handle the case load.
Professor MacIntyre adds: “One case may have 10-25 contacts, so if there are 100 cases in a day, you need to trace 1,000-2,500 contacts within 24 hours.”
But let’s break it down further.
“The contact tracing questionnaires take some time … on an average day, an eight-hour work shift with an hour off, you’re probably only going to be able to do seven to 10 people,” Professor McLaws says.
4. Time spent working with cases
Professor McLaws says this is why the amount of time contact tracers have to work with individual cases is crucial.
“It takes quite some time; you wouldn’t be able to do it in less than half an hour, given you’re talking to somebody who’s just had a very unpleasant diagnosis of a potentially serious infection.
“So, they’re not going to feel very happy, and you’ve just contacted them within 24 hours, and now you’re asking them a whole lot of questions, asking them to look back and think about who they’ve come into contact with, and they’ve got to think back sometimes up to 14 days.”
5. Building trust and empathy
While anyone could (theoretically) understand the questionnaire confirmed cases need to answer, some are more prescriptive than others, Professor McLaws says.
So, some require the contact tracer to go through the questionnaire step-by-step, whereas others allow the tracer to change the discourse or “the attack”, she explains.
This is significant.
“This can actually alter the ability of the case that you’ve now contacted to respond well or not respond well, because if they’re thinking you’re talking off a script, they may feel less close to you, less engaged, or they may be happy for you to talk off a script; they feel safe, because you’re not making a subjective evaluation of them.
“So, [contact tracers] have to demonstrate great tact and empathy.”
If engaging the coronavirus case whose contacts you’re trying to trace becomes a problem, Professor McLaws says they might become an unknown case (sometimes also known as a mystery case).
“Because people won’t want to share [the information needed] with you if they think they’re going to be value-judged. And you can’t build trust when you’re pushed for time.”
So what do the states and territories need to improve on?
Professor MacIntyre says Victoria’s experience is the clearest example of what happens when you don’t have the resources to trace contacts, and trace them fast.
“It spirals out of control,” she says.
“One of the biggest problems in Victoria was severe under-resourcing.
“NSW has done it well and squashed every outbreak so far, by rapid and thorough contact tracing.”
Meanwhile, Professor McLaws says she’d like to see public health officers and contact tracers question where they could improve their depth of drilling down.
Part of contact tracing is deciding whether somebody has had significant exposure and whether they can stay at home safely so clusters don’t start in households, she explains.
“If you don’t have any symptoms and you’re considered to be an unimportant contact, then you may slip through the cracks because you’re not going to be tested.
“But we do know that 14 to 20 per cent of cases are asymptomatic. So we also need to do much more testing.”