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The UK’s Covid-19 testing system is in disarray. Unable to manage a backlog of nearly 200,000 tests, completed swabs are being sent to laboratories in Italy and Germany for processing. Across the country, people are being asked to travel hundreds of miles in order to secure tests. Many in the northwest – the region with the highest rate of new infections – can’t access tests at all.
But testing is only the first step in slowing the transmission of Covid-19. Since the start of the pandemic public health experts have extolled the importance of test, trace and isolate: the trifecta of interventions designed to stop those infected with the virus transmitting it to others. On May 28 the government launched a programme, called NHS Test and Trace, designed to intercept the virus before it could be passed on. Yet the data suggests that contact tracing in the UK isn’t working, and it’s failing worst in regions that are already hardest-hit by the latest wave of infections.
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Here’s how Test and Trace is supposed to work. If you test positive for the coronavirus, your contact details are passed to the NHS Test and Trace service. If your case involved a hospital, healthcare setting, prison, or other similar locations, it’s marked as “complex” and passed to local health protection teams. All other cases are marked as “non-complex” and these people are contacted by NHS Test and Trace and asked to give details of everyone they’ve had close contact with recently. NHS Test and Trace then contacts those people and advises them to self-isolate for 14 days and get a test if they start showing symptoms.
If it worked perfectly, this would mean everyone with a positive test result self-isolated (along with their household), plus all of their close contacts too. “You have to test sufficient numbers of people with symptoms, you then have to trace sufficient numbers of their contacts and isolate combinations of everybody who is positive in order to keep the virus out,” says Jasmina Panovska-Griffiths, a senior research fellow at University College London and the author of a paper that modelled how different levels of contact tracing would impact the spread of the virus when schools reopened.
Combining testing, tracing and isolation is key to the whole plan, says Panovska-Griffiths. If you’re not tracing enough people, then you need to step up testing to find people with the virus. “We need to increase both the testing and the tracing, or increase one to compensate for the other,” she says.
But in parts of the UK contact tracing is seriously underperforming. Bradford currently has the second-highest rate of Covid-19 infections in the country, according to the most recent weekly coronavirus surveillance report. Between the launch of NHS Test and Trace on May 28 and September 2, contact tracers were only able to reach 42.5 per cent of the identified non-complex close contacts of cases in Bradford. In Blackburn with Darwen, which is the fifth worst-hit region currently, contact tracers only reached 48 per cent of identified close contacts. In Oldham, the third worst-hit region, the figure is 50.9 per cent.
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For England as a whole over this time period, the average number of non-complex identified contacts reached and asked to self-isolate was 58.3 per cent. Of the ten regions with the highest rate of transmission in the UK only one exceeded this average rate of contact tracing: Salford, where 59.7 per cent of close contacts identified were reached.
These figures cover the entire period from late May until earlier September, and there are signs that contact tracing has slightly improved since its launch. Between August 27 and September 2, NHS Test and Trace reached 61.3 per cent of identified non-complex close contacts, an increase from 52.5 per cent at the start of Test and Trace although this figure has not improved since mid-July. In the latest report, which adds the week of September 2 to September 9, the percentage of identified close contacts reached has improved slightly in most of the region with the highest rates of infection. The Department of Health and Social Care did not respond to a request for comment in time for publication.
All along the chain of test, trace and isolate, people are being missed by the system. “There’s been a real issue with access to tests, so it means that we’re only ever uncovering the tip of the iceberg. We don’t know how many other people out there who have not managed to get tested who have got the disease and are not being traced,” says Andrew Lee, a reader of public health at the University of Sheffield. People who do get a test are facing extended waits for results. The median time for a result from a home testing kit is now 82 hours, according to the most recent figures, while for in-person tests at regional test sites the wait is 27 hours.
Even when people do get a positive test and are referred to the Test and Trace system, people may not know the contact details of all their close contacts, or may refuse to supply them. People who are contacted by Test and Trace and advised to self-isolate may choose – or be unable – to comply with the advice. One UK study from May found that 75 per cent of people who had symptoms, or were part of a household with a symptomatic person, did not follow the self-isolation guidelines.
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“The most important ingredient [of test, trace and isolate] is to isolate if you’re ill,” says Lee. “It doesn’t matter what your test results are or when you have your test – if you’re ill and you stay at home, straight away you’ve limited the risk of transmission.”
But if people aren’t contacted by NHS Test and Trace, there’s no way they can be told to self-isolate. Part of the problem might be that non-complex cases are dealt with by the centralised NHS Test and Trace service, who struggle to adapt to circumstances specific to local communities. “Rather than spending £100 billion on a moonshot idea you’d be much better off giving a fraction of that to local authority public health teams to manage and respond to the situation,” Lee says.
Matt Reynolds is WIRED’s science editor. He tweets from @mattsreynolds1
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