COVID-19 Contact Tracing is not an App*
*this is likely of more relevance to people in the UK but hopefully it helps explain things a little
I’ve been involved in the response to COVID-19 and I’ve learned a lot about the virus and the general response whilst working on a few different things.
One of those things was directly related to contact tracing.
Every day a new story appears about the latest App that’s going to save us all.
Then it isn’t ready, and it goes away again.
Everyone asks ‘but how can we do contact tracing now??? (Not everyone, but certainly news outlets.)
This is driving me nuts, because the App is not the answer, so let me try to explain things a little.
Contact tracing: The reality
Contact tracing is a challenge, but it is not complex.
To reduce the spread of COVID-19 we need to be able to identify people who have the virus, ensure they self isolate and receive the necessary guidance on what to do if their illness becomes more severe.
We also need to identify people that people with positive test results have been in contact with, so we can ask them to isolate.
This typically happens with contact tracers (humans) contacting the person who has tested positive (usually by phone) and asking them some questions, and identifying their close contacts. They then contact the close contacts to check if they are symptomatic, and to ask them to self isolate.
We do this to stop the disease spreading and affecting the most vulnerable people and preventing the number of deaths from the virus. We can also use this process to support the easing of lockdown restrictions.
Some of the data captured is in service of contact tracing. Some of the data is in service of data modelling to understand where the disease is and where perhaps increased restrictions on movement may be necessary for everyone’s safety.
Sometimes, people who don’t appear to be sick, do have the virus, and they can unknowingly pass the virus on to other people.
The data captured as part of contact tracing can help identify this type of scenario and identify people who really need to self isolate to stop the virus spreading further.
No app here.
Why testing matters
Testing is the only clear way of identifying where the virus is. Symptom tracking is an important source of information, but it is not as definite as a positive test result.
Knowing where the virus is, means we can understand better where and when we can provide support and where and when we can reduce restrictions on movement.
For it to be really effective we need to do lots of testing. To support that effort, digital solutions can help with booking tests and logistics, the sharing of test results quickly, and being able to rapidly notify people who have been tested of the outcome, encouraging them to continue to self isolate and seek help if needed.
There are two types of tests, one that checks if you have the virus right now (which is what is being used widely at the moment) and another which can tell you if you had the virus in the past.
No app here.
So Apps then?
The ‘App’ in the news is a ‘Proximity tracking App’. This is explained over and over again, so i’ll not spend too long on it, there are more or less two types:
- Centralised, where information is gathered and stored centrally and people can be identified
- Decentralised, where information is stored centrally, but is entirely anonymous and is only used to notify ‘things’
The decentralised model
A decentralised app basically uses bluetooth on your phone to ‘check’ what other bluetooth devices are near it does this every minute or so. It doesn’t know who you are or who the other phones are, they are just ‘things’ with a unique number.
If someone who uses the app has a positive test, they can tell the app. The app then sends a message to all the ‘things’ it has seen to tell them they have been near they should self isolate. The ‘things’ that get the message are phones, and usually have owners who are people, so those people should now be isolating.
That’s the most basic version. Nobody knows who anyone was in this chain.
Why is this good? Because it is quicker than calling the person with a positive test result and asking them to remember who they were near, they might not know them all, and may not remember, then, calling all the people they could remember and telling them to isolate, it happens quicker, and potentially slows down the spread of the disease.
For this to be super effective, the people who were near the person with a positive test need to isolate immediately and get tested quickly so they can understand if they have the virus and seek guidance and help, or if they can stop isolating and get back to whatever they need to do.
The challenge here is that we don’t know where anyone was in this little group immediately so we don’t know where the disease is, but, when they request a test, we do get that information (without building up a list of people they were near)
This is why privacy advocates prefer this model.
The centralised model
It works the same as above, however, the person who downloads the app supplies some personal information to a ‘server’, so it’s not anonymous.
The benefit here is that you get an idea of where the disease is at the expense of privacy.
Who is doing what with Apps?
MIT have a great list of what different countries are doing.
Personally I love the Iceland memory aid App, it helps contact tracing by acting as a prompt to remember where you were and who you were with.
Self Tracing
I’ve sort of named this, but bear with me.
This is the first bit above, contact tracing, but you volunteer your own information, so instead of someone ringing you, you provide your details to the contact tracing team directly.
This potentially means better information (you can take your time without the pressure of keeping someone waiting on a phone), less phone calls being made (so possibly quicker), and, for people, they are actively contributing in a small way to keeping others safe.
This isn’t the App either (although it could a part of it).
Hopefully this helps explain things a bit. The key things to take away here are:
Contact tracing is not an App, it is a process by which someone who has the virus identifies others they may have been in contact with that could be at risk. This is so they can self isolate and get tested.
Testing is critical to the success of this approach. We need to know where the virus is, so we can ease restrictions (or put them back in place) when appropriate.
The proximity app is a piece of the puzzle, but it is neither critical nor useless. It can help. How much depends on how many people use it. But again, testing is a key part.
Self tracing is another piece of the puzzle.
Ultimately effective treatments, anti-body testing (which tells you if you had the virus in the past) and a vaccine are how we can move on to a new version of the world, where we can ease restrictions on movement and people can get on with getting on safely.
