Public health v private lives
Your phone could log all your social contacts, to have authorities trace possible Covid19 infections. But would we want it to? Nikki Macdonald examines the tradeoffs between privacy and disease control.
Can you remember everyone you stopped to chat to in the past two days? The people you sat beside on the bus? The people next to you in the cinema, when cinemas were still a thing?
What if your phone could log all those contacts as they happened, storing them up for the moment you – or any of those people you hung out with – were diagnosed with Covid-19.
That’s exactly how some countries have been speeding up the laborious process of tracing the movements of an infected person, to find those to whom they may have passed the disease.
But the idea of governments tracking the minutiae of their citizens’ movements – where they go and who they spend time with – has raised obvious privacy concerns. So is the tradeoff worth it?
Contact tracing
There are two characteristics of Covid-19 that make contact tracing critical to its control.
The first is that some people experience such minor symptoms they will never be identified as having the disease. Which means they can be merrily spreading the virus without anyone knowing. Experts call this silent transmission.
The second is that people can be infectious for 24-48 hours before they get any symptoms. There’s no clear consensus on what proportion of new cases have been infected by people who are pre-symptomatic, or who never develop symptoms. Estimates vary from 10 per cent to almost half of all transmissions.
If you can identify those people and isolate them before they become infectious and pass on the disease, you can stop the disease in its tracks, says Otago University public health professor Michael Baker.
‘‘If they’re in quarantine they can’t infect anyone else over that time. So the faster you identify those people and get them quarantined, the more successful you’ll be in stopping those lines of transmission.’’
New Zealand’s four-week shutdown should knock out most community transmission, because if everyone stays home the virus has nowhere to go. But not everyone will do what they’re told, and with Kiwis still returning home and essential service workers still moving around, Covid-19 cases will continue, Baker says.
That means New Zealand will need to have testing, and contacttracing going ‘‘full bore’’ after the four-week lockdown ends.
Otago University infectious diseases doctor Ayesha Verrall says New Zealand needs to urgently ramp up its contact tracing capacity in preparation for coming out of lockdown.
‘‘We should aim to leave the lockdown in one month with the ability to identify and trace the contacts of 1000 cases a day,’’ Verrall says. ‘‘We are currently struggling with 50.’’
That’s despite the Health Ministry putting on a team of extra people to help public health staff.
The problem is that the manual process of sitting down with a public health worker and trying to reconstruct every tiny detail of the past few days of one’s life is laborious, timeconsuming, labour-intensive and probably not that accurate.
And those wasted hours mean wasted opportunities to prevent the disease spreading. As Baker puts it, ‘‘time is the enemy here’’.
A code for us all
But what if you could track all those contacts as they happen, creating a neat little record of daily interactions that can be immediately tapped into as soon as someone is diagnosed with Covid-19.
It’s not science fiction. China pioneered this approach, after it relaxed its lockdown measures. Using an extension to the WeChat app, authorities controlled movement and entry to public spaces and public transport. Each person was assigned a green, orange or red code according to their health status, which allowed either free movement, local movement or no movement (ie quarantine).
The system tracks people’s movements using GPS location data and QR code scanning. But it also tracks who they interact with – by getting phones to talk to each other to log close contacts between people. Then when someone returns a positive test, that’s automatically fed into the system and all that person’s close contacts are alerted, and their quarantine status changed.
The major benefit is that it allows health workers to get on top of the disease without full lockdown.
But the surveillance comes with obvious Big Brother privacy risks – should governments really be able to track everywhere you go and who you hang out with? In China, there were concerns the information was being shared with police.
In South Korea, when a new case was identified, authorities sent ‘‘safety guidance texts’’ with links to a list of every place that person went to before being hospitalised. The information was detailed enough that disease victims could sometimes be identified, leading to public shaming. In one case, it reportedly exposed an extramarital affair.
On Friday, Singapore released its own app, called TraceTogether. One security feature it includes is that all the location and contact information is encrypted and stored on the phone itself. That means the data can be accessed only by health authorities when someone tests positive for the disease.