If and when New Zealand exits alert level four and its restrictions, contact tracing becomes the most important tool we have to prevent having to lockdown all over again. So what does it involve, and are we doing enough of it?

Just quickly – what is contact tracing? 

Contact tracing is what happens to determine which people a probable or confirmed case has been in contact with, and how closely. There are two main focuses for contact tracing: close contacts and casual contacts.

The first group is much more important to trace, because if someone has Covid-19, their close contacts have a higher likelihood of also having it. Close contacts range along a spectrum from those who have had direct contact with the bodily fluid of an infected person, to having sat within two metres of them for more than 15 minutes.

A casual contact is described as “any person with exposure to the case who does not meet the criteria for a close contact”. That could mean sitting on the same plane, but four rows of seats back, for example. Casual contacts are much less likely to pick up Covid-19 from an infected person, but it is still possible. That’s a big part of the reason events like Polyfest and the March 15 commemorations in Christchurch were cancelled last month – there would simply have been far too many casual and close contacts to trace, made harder by the fact they’re unticketed events.

Those who have been in close contact with a confirmed or suspected case of Covid-19 need to go into self-isolation immediately, and monitor themselves for symptoms for 14 days.

So how does the contact tracing actually work?

At the moment, it involves people with confirmed or probable cases saying where they’ve been, for how long and with whom over a period of time, and then health workers try and get in touch with all of those people. A couple of different groups are currently working on this. The first group is staff at Public Health Units attached to DHBs, and the second is the new workforce attached to the National Close Contact Service, which is part of the Ministry of Health.

The standard process for this has been a two-stage process, by which a person is first interviewed by a case manager to get their details, and then contact tracers follow up with those people who are named. As you can probably imagine, it’s not flawless – someone might forget a contact, or forget someone’s name in the original interview, meaning that a potential close contact can’t be followed up.

And how is it all going so far?

That depends who you ask. “As of Saturday, 4,909 close contacts had been traced by the NCCS since it was stood up on March 24, with 702 contacts traced in a single day on Thursday,” said NZ’s director of public health Dr Caroline McElnay in a Sunday media release. “Originally it was making 760 calls a day – now that’s more than 2,000.”

Those numbers might sound like a lot, and they’re certainly moving in the right direction. But Otago University public health expert Dr Ayesha Verrall says while the increase in capacity is really good, there are still unanswered questions.

Such as? 

“The speed is really important, and whether we can be fast enough with the tools that we have,” Verrall told The Spinoff. If a contact isn’t traced for several days after being in contact with an infected person, that increases the likelihood that they in turn will unwittingly pass Covid-19 on.

The other issue Verrall highlighted was the scale, and whether it could be enlarged quickly. “I think they need to be able to trace about 1,000 cases a day. So they’re doing 700 contacts at the moment, but every case could have multiple contacts. At the moment, we will have very few contacts because we’re in small bubbles, but in the future that could increase, especially if we’re at level three.”

Why does this matter so much to the wider effort to fight Covid-19?

Theoretically, if we stayed in lockdown forever we’d barely need to scale up the contact tracing system. But that isn’t going to happen – and our ability to leave lockdowns (and stay out of them) will be determined how comprehensively we can do contact tracing. “It’s our fire extinguisher,” said Verrall, “and we want a giant fire extinguisher before we go into lockdown and hide from the fire.”

“Unless you know how many cases you can trace, you don’t know what your epidemiological trigger is for going into lockdown,” said Verrall. She offered some maths which put it into context.

“Let’s say we can trace 100 cases and their contacts a day – 700 contacts probably relates to about 100 cases, at about seven per case. So if we can trace 100 cases nationwide, that means the next time we have 100 new cases in a day we have to go into lockdown. We’re actually nearly at that already, because we’re getting 80 cases a day, so our current contact tracing capacity isn’t much better than our control of the outbreak. So it looks like we can’t leave lockdown any time soon.”

Bugger. What can be done to improve this all?

There are a few mechanisms which will increase the capacity, over and above the Ministry of Health and district health boards getting more staff tooled up and ready to go. One category is quite basic – we all just become a lot better at recording where we’ve been, and with who. For those who get a bit of a thrill from signing the visitor book at a Cosmopolitan Club in an unfamiliar town, expect that sort of system to be in place at every venue as we come out of lockdown, and the signing to be compulsory. If you went to a pub in the few days we were at alert level three, you should have been asked to sign in.

The other thing that could help a lot is an app, or some other digital service that automates a lot of this process. The government is currently working on just such an app, with mobile phone tracking capability. Given human memory is often flawed (saying you stopped to chat with “the guy in the mall in a stripy jumper” doesn’t quite cut it) this would dramatically increase the capacity of the contact tracing system – provided people signed up for it in large enough numbers. It would also allow automation – rather than someone having to call you when they get through their existing backlog, it could immediately send a message to all those who were on the same bus as a confirmed case, for example. A free app in Singapore – called Trace Together, is considered to be a world-leading piece of software, and has contributed to that country’s case numbers staying relatively low.

Isn’t cellphone tracking for this a bit creepy? 

Such a system would raise serious privacy concerns. Auckland University’s Dr Andrew Chen has looked into this issue, arguing that while governments already have the legal ability to do this, there are ethical considerations with mass surveillance that need to be taken into account as well.

“Using cellphone data to track people for the purposes of contact tracing may be acceptable to some, but for others it will make them feel uncomfortable and undermine their confidence in government,” he said. “At a time when morale and trust in government are critical for stability and encouraging compliance, the risk of alienating people is a real concern.”

The Ministry of Health says it is taking these sorts of concerns into account.

The face mask question is more complicated than it might at first seem, explains Siouxsie Wiles.

The Spinoff’s coverage of the Covid-19 crisis is only possible because of the support of members. If you can, please consider joining Spinoff Members here. Read Toby Morris’s new Side Eye comic, created with Siouxsie Wiles, here. And more of Siouxsie’s writing here.

Maybe you’ve seen the graph that says those countries where everyone wears a mask are the ones that have managed to keep Covid-19 under control? The first thing to say about that claim is that those countries also did lots of other things, too – they acted fast, with intense testing, contact tracing and quarantine.

The reality is, when it comes to wearing a face mask there are pros and cons that differ depending on where in the world you are. I’ll get to these shortly. But this is a complicated one. Even the experts can’t agree on whether everyone should be wearing one. That’s raised accusations of racism as well as given life to several conspiracy theories. Face masks have become such a heated topic over the last few weeks that I’ve personally been harassed and threatened over it.

Until now, the WHO has recommended that if you are healthy, you need only to wear a mask if you are taking care of a person with suspected Covid-19. They also recommend wearing a mask if you are coughing or sneezing. The WHO has now convened a group to review new evidence to see whether or not they should update those recommendations. Which is the right thing to do.

The different kinds of face masks

There are lots of different types of face masks. The three you have probably heard mentioned are N95 respirators, surgical masks, and cloth or home-made masks.

N95s are designed to protect the wearer from breathing in or swallowing droplets and very small particles – like bacteria and viruses. To work, N95s need to form a tight seal around your face. That means first having a “fit test” to ensure the mask forms a proper seal. If you’ve a beard, forget it. Because N95s are designed to form a tight seal they can become very uncomfortable as heat and humidity build up. As with all masks, people need training to put them on and off without contaminating themselves or the mask. Importantly, N95s are needed by healthcare workers who are caring for people with Covid-19 and have the biggest risk of getting infected. They form one part of their PPE – personal protective equipment.

Surgical masks are disposable, loose-fitting face masks that cover your nose, mouth and chin. They’re mainly used to protect the wearer from sprays and splashes, or to stop the wearer from spreading their respiratory secretions to others – like a patient during surgery. Cloth masks are homemade versions of surgical masks made out of whatever you have to hand.

Will surgical and cloth masks help stop the spread of Covid-19?

Because of what they are made of and how they fit, surgical and cloth masks are unlikely to stop you catching Covid-19. But the question everyone is asking is: do they play a role in stopping the spread of the virus? The prevention of spread has become especially important as understanding of how the virus transmits has changed.

At first it was thought the virus was spread through droplets from people with symptoms. Now it’s understood that people can shed the virus even before they have symptoms. And some people may shed the virus without ever developing symptoms. Precisely how many people do this isn’t known. There is now also a worry that people can spread the virus through talking and singing.

This is why physical distancing is so important and why the distance we need to stay away from other people has changed. First it was one metre. Now it’s two. A new study might see that revised again. Dr Lydia Bourouiba is an associate professor at the Massachusetts Institute of Technology in the US. She runs the very appropriately named Fluid Dynamics of Disease Transmission Laboratory and used a high-speed camera to film a healthy person coughing and sneezing. Some of the droplets from a vigorous sneeze travelled as far as seven or eight metres. So, if you are someone who fancies having a glass of wine with neighbours from two metres away, don’t. Do it online instead.

But back to the original question: can masks play a role in stopping the spread of Covid-19? It’s too early for studies yet about this particular coronavirus but a study on influenza has just been published in the journal Emerging Infectious Diseases. The authors looked at the data from the 10 randomised controlled trials and showed overall, wearing surgical masks didn’t do anything to reduce the spread of influenza.

On the other hand, an analysis of SARS trials, which is caused by a related coronavirus, did show some effect. Overall, one infection was prevented for every six people who wore a surgical mask. That said, hand-washing was much more effective. But it doesn’t mean we can’t do both, right?

In the last few days, another study has just been published that looked at whether surgical face masks could prevent transmission of human coronaviruses (though not Covid-19) and influenza viruses from people with symptoms. They collected the breath of 123 people who they knew had influenza (43 people) or the rhinoviruses (54 people) and coronaviruses (17 people) that cause the common cold. Some of these people were randomly allocated to wear a face mask when the researchers collected their breath. The rest didn’t wear a mask. The researchers then looked for viruses in everyone’s exhaled breath. The first thing to note is that the number of people in the study is small. With that in mind, they were only able to detect coronavirus from roughly four out of 10 people when they weren’t wearing a surgical face mask. If the Covid-19 coronavirus behaves in a similar way, then this study suggests not everyone will be shedding virus every time they breathe out. But the even better news is that they weren’t able to detect any virus when people were wearing a surgical mask.

Why I’ve been reluctant to recommend masks for everyone – at least here in New Zealand

Quite a few reasons. A bit like what happened with hand sanitiser, I was really concerned that if everyone rushed out to buy face masks then those who really needed them would go without. I was also really worried that people would feel a false sense of security and then not do all the things that will help protect them and others from Covid-19. And every time I’ve gone to the supermarket I’ve seen evidence of this.

One of the reasons you’ll see advice about mask wearing changing is partly because new evidence is coming to light, like the studies I’ve mentioned. But it’s also because there are many places where the virus is spreading exponentially, and many people are still going about their business. In this scenario, the more people who wear masks, the more likely those who are infected but don’t know it will be wearing one. And that will help capture at least some virus-laden droplets which should help reduce transmission. In other words, the pros vastly outweigh the cons.

So, if you are living in a place with widespread community transmission of Covid-19, please wear a mask. And if you are living in New Zealand, where we are all in our bubbles and aren’t seeing exponential spread of the virus? Then check out one of the excellent tutorials on making your own face mask and wear it when you go out to the supermarket or to access other essential services. That way you’ll be protecting our essential workers.

But promise me this. That’ll you’ll wash your hands before you put your mask on, and then again once you’ve got it on. That you won’t touch it while you are wearing it. And, if you do, you’ll immediately wash your hands. That you will wash it after every use and allow it to dry properly before using it again. And that you’ll keep up with regular hand-washing and physical distancing.