That puts it at odds with the NHS app, which instead relies on users self-diagnosing via an on-screen questionnaire.

UK health chiefs have said the questionnaire is a key reason they are pursuing a “centralised” design despite privacy campaigners’ protests.

Germany ditched that model in April.

And on Wednesday Chancellor Angela Merkel said there would be a “much higher level of acceptance” for a decentralised approach, which is designed to offer a higher degree of anonymity.
Image copyright EPA
Image caption Germany’s chancellor believes a decentralised app will be more popular

Automated contact tracing uses smartphones to register when their owners are in close proximity for significant amounts of time.

If someone is later found to have the virus, a warning can be sent to others they may have infected, telling them to get tested themselves and possibly go into quarantine.

In the centralised model, the contact-matching happens on a remote computer server.

And the UK’s National Cyber Security Centre has said this will enable it to catch attackers trying to abuse the self-diagnosis system.

By contrast, the decentralised version carries out the process on the phones themselves.

And there is no central database that could be used to re-identify individuals and reveal with whom they had had spent time.

BBC News technology correspondent Rory Cellan-Jones said: "The NHS is taking a big gamble in choosing to alert app users when they have been in contact with someone who has merely reported symptoms.

“It could make the app fast and effective - or it could mean users become exasperated by a blizzard of false alarms.”

Ms Merkel said SAP and Deutsche Telekom - which are co-developing Germany’s app - were waiting for Google and Apple to release a software interface before they could complete their work.

And BBC News has learned the two US technology companies plan to release the finished version of their API (application programming interface) as soon as Thursday.
False alerts

Details of Germany’s Corona-Warn-App published on the code-sharing site Github say it depends solely on medical test results to “avoid misuse”.
Media captionWatch: What is contact tracing and how does it work?

Those who test positive will be given a verification code that must be entered into the app before it anonymously flags them as being a risk to others.

Germany has led the way in testing in Europe and currently has capacity to analyse about 838,000 samples per week.

The UK is catching up - but scientists advising the NHS say they can save more lives by also drawing on self-diagnosis data.

“Speed is of the essence,” Prof Christophe Fraser, of the Oxford Big Data Institute, said last week.

It can take several days to obtain Covid-19 test results.

And self-reported symptoms can be acted on instantly.

But an ethics advisory board advising Health Secretary Matt Hancock on the app has warned too many resulting “false positive alerts could undermine trust in the app and cause undue stress to users”.

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The NHS is currently trialling its app on the Isle of Wight.

There have been reports of some suspected false alerts.

But a Department of Health spokeswoman said this had been expected.

“In a matter of days, more than 50,000 people have downloaded the app with overwhelmingly positive feedback,” she told BBC News.

“But as with all new technologies, there will be issues that need to be resolved in how it works, which is why it is being trialled before a national rollout.”

The NHS is also exploring use of the Apple-Google API, which would entail a switch to the decentralised model.

But it intends to offer users the centralised version first, unless plans to complete the rollout within a fortnight go awry.
Image copyright Reuters
Image caption Norway’s data regulator is at odds with the country’s’ National Institute of Public Health about its contact-tracing app

One sticking point could be calls for limits on how the data is used - possibly requiring a new law.

That would avoid the risk of a repeat of the situation in Norway, where the local data protection watchdog has accused the country’s health authority of failing to carry out a proper risk assessment of a centralised contact-tracing app.

After years in which it seemed the local surgery was stuck in the digital dark ages, many have leapfrogged into the future in a matter of weeks, offering online and video consultations to patients.

Much of the change has been led by a tiny start-up whose whole approach has been deliberately low tech. Two years ago, AccuRx started offering a service that allows GP practices to communicate with their patients by text message - an “embarrassingly simple messaging solution” as founder Jacob Haddad puts it.

“No AI, no blockchain,” he laughs.

Despite many practices still struggling to move out of the fax machine era, it proved popular. By early March, about half of all the GPs in England, and some in Wales, were using the service to tell patients their test results were fine or they could pick up a prescription.

Then, as it became clear that Covid-19 was going to have a big impact, AccuRx started offering new services that would make it easier for surgeries to deal with patients remotely.

“We’ve just been all hands on deck, getting features out,” says Mr Haddad.

“Video consultations, a facility to send documents to patients and get responses, remote monitoring of patients.”

Again, the approach has been pretty low-tech, designed to work with whatever devices doctors and patients may have.

The consultations usually start with a simple phone call, then if the GP decides they want to see something - perhaps a rash - the patient is sent a text with a link to activate a video call.

• I was given a demonstration. When I clicked on the link, I was given a choice either to install an app or to use the phone’s browser.

• I chose the browser option, and although the video quality was not brilliant, it did the job.

From a standing start at the beginning of March, AccuRx’s video consultations have taken off, and are now running at 35,000 a day.

With all sorts of practices suddenly eager to find new ways of working, more than 90% of GPs across England have signed up.

Surely, then, it must be coining it? No, because right now its services are free, although the company is hoping that in the longer term the NHS and other health services around the world will pay for its products.

Like many an ambitious young tech start-up, the firm is “pre-revenue”. It’s backed by about £9m of venture capital money from investors, who hope the “build it and they will come” philosophy will lead to big returns. It is growing fast but still has just 31 employees.

An even younger smaller operation is also showing how the doctor-patient relationship can be transformed in the smartphone era.

Just six weeks ago, an entrepreneurial GP, Dr Alexander Finlayson, launched NYE Health.

He describes it as a way to make the clinician’s own device - whether that’s their phone, tablet or desktop web browser - “NHS-compliant”.
Image copyright NYE Health

It means that doctors - whether in hospital or GP surgeries - can have video and audio conversations with patients or with other health workers in a secure way.

Dr Finlayson, who has worked on global health projects in Somalia and elsewhere, says NYE had been under way as a theoretical project for a while.

When confronted with the coronavirus crisis, he and a team of designers, engineers, and clinicians put the product together over an intense three-day brainstorming session.

It was released on 13 March and has already done tens of thousands of consultations, with users everywhere from intensive therapy units to dermatology departments and GP surgeries.

Just like AccuRx, NYE is pre-revenue and has not really thought much yet about a business model.

But it has already attracted interest from potential overseas customers and is being advised by Twitter’s co-founder Biz Stone. Only 18 people are working on the project, but it sounds as though they could soon need to recruit many more.

The trailblazer for video consultations in the UK was Babylon, which offers the GP at Hand service.

This provides an alternative to the GP surgery and has proved popular with time-poor young professionals in London, who can book a video consultation at short notice rather than wait weeks to see the doctor.

Babylon, which also makes great play of its work applying artificial intelligence to healthcare, raised $550m (£439m) last year from backers including the Saudi Sovereign Wealth Fund, at a valuation of $2bn.

You might think that this was a business expanding rapidly during the current health crisis. Instead it is taking advantage of the government’s job retention scheme to furlough 5% of its 2,000-strong workforce.

In a letter to staff, chief executive Ali Parsa said ideas his company had pioneered, such as the provision of healthcare on a mobile phone, had now become commonplace.

“There are many others who are doing the same thing and the current crisis has forced mass adoption and commoditisation of these technologies,” he wrote.

A spokesman told me that Babylon no longer considered itself a telemedicine company, and was shifting its focus to AI.

It seems the disrupter has been disrupted, and minnows like AccuRx and NYE may play a bigger role in transforming healthcare delivery in the UK than the mighty Babylon.