London: Not everyone who shows symptoms of coronavirus will be tested for the disease in the UK. In fact, as it stands, it’s more likely you won’t be tested, despite the World Health Organisation (WHO) urging countries to “test, test, test”.

WHO director-general, Tedros Adhanom Ghebreyesus, told reporters at a virtual press conference: “We have a simple message for all countries: test, test, test. Test every suspected case, if they test positive, isolate them and find out who they have been in contact with two days before they developed symptoms and test those people, too.”

The call to action came just days after the UK announced it would be distinctly moving away from community testing for Covid-19.

Public Health England (PHE), together with NHS England and the Department of Health and Social Care (DHSC), said testing would be prioritised for those most at risk of severe illness from the virus. “Our aim is to save lives, protect the most vulnerable, and relieve pressure on our NHS,” PHE said in a statement.

The move left many confused – individuals with symptoms are being urged to stay indoors and self-isolate for seven days, while people who live with others are now urged to all stay at home for 14 days if one person displays symptoms.

Chief medical officer for England, Professor Chris Whitty, believes testing efforts in the UK are already “substantial”, with more than 44,000 tests conducted. China has issued the most tests so far, followed by South Korea, Italy and Russia, according to analysis by Our World In Data. The UK comes in fifth place.

South Korea is reportedly processing around 10,000 tests a day. Its foreign minister said testing was “the key behind our very low fatality rate”. In comparison, PHE was only processing 1,500 tests a day across the UK until last week, when it revealed NHS labs would start testing swabs from hospital patients, enabling 8,000 more samples to be analysed every day. But it’s not known whether this capacity is currently being reached.

If we’re not testing everyone with symptoms, we don’t know how many people actually have the virus. So what’s going on?

Professor Trudie Lang, director of the Global Health Network, University of Oxford, tells HuffPost UK it’s important to be clear on what we mean by “testing”. It doesn’t mean taking people’s temperatures at airports – that’s known as potential case detection, which is “very different”.

Rather, the main method of testing used in the UK right now is where a swab is taken from a person’s upper respiratory system (so the nose or mouth) and then sent to approved labs in the UK, run by PHE and NHS, where trained staff then determine whether the virus is present.

“It’s quite a difficult test and it requires the right equipment, trained people and it has to be validated – they do cross-checking across the labs to make sure it’s absolutely accurate,” says Prof Lang.

Professor Lang believes the UK has been testing “really high numbers” compared to other countries – and while it’s “absolutely right” that WHO urged countries to “test, test, test”, the situation in the UK is that “testing is being rolled out relative to the ability of the health care system to put it in place,” she says.

While she believes the testing strategy has been “comprehensively put in place” in the UK, she said it’s also limited by the process itself – the healthcare system has to take the samples from the patient safely, away from other hospital patients, and get the results back to them and act on it quickly.

And the government’s chief scientific adviser Sir Patrick Vallance offered a similar reason. He acknowledged more testing is needed, but said there isn’t capacity to do so. Speaking to the Health and Social Care Committee on Tuesday 17 March, he said: “We need to use the testing in the right place at the moment.

“We simply don’t have mass testing available for the population now – and there’s a big effort going on to try and get that in place as quickly as possible to be able to manage this.”

As it stands, tests are being primarily offered to patients in critical care or who require hospital admission for pneumonia, acute respiratory distress syndrome or flu-like illness, and where an outbreak has occurred in a residential or care setting, like a care facility or prison.

Initially, back in February, the UK started with community testing. This meant people could call up their GP or NHS 111 if they had symptoms and had come back from a high-risk country. They were told to attend a community hub or drive-through testing facility. There were even pilots in London where medical staff would visit people in their homes. However last week, health officials said they had to prioritise those most at risk.

On Monday, Prof Whitty defended the UK’s move away from community testing and said there was “complete surveillance testing” in intensive care. Pneumonia patients are also being tested in hospitals, he said, and GPs are testing in the community – it’s believed he was referring to areas where there has been ongoing surveillance testing, where selected GP practices test patients and submit samples, even if they have not travelled to an area affected by Covid-19 or don’t show symptoms. The aim of this is to monitor the disease’s spread.

Sir Vallance confirmed that PHE is looking at other tests that might work in the community and said community testing would be reintroduced as and when capacity allows.

On 15 March, Scotland’s government said testing would be extended to communities but there wouldn’t be testing in place for those with minor symptoms. It also said enhanced surveillance testing would be operating in hospitals – meaning patients without symptoms would be tested too.

One type of test Prof Lang and other academics are hopeful for is serology testing, which is in development. This is a type of blood test that looks for antibodies in your blood and can tell whether you’ve had Covid-19 or not.

“If you have antibodies it means you’ve had the infection, you’ve cleared it and you’re immune – that would be really helpful for protecting health workers,” says Prof Lang.

Another test which would be “ideal” to have, she continues, would be a ‘point of care’ test, which would tell patients whether they have the virus there and then, rather than requiring laboratory analysis – and the 24-hour (sometimes longer) wait to get test results back.

However, it’s not known yet when either of these tests will be available for use.

Perhaps most urgent is the need for testing health workers on the frontline right now. At the time of writing, 800,000 people had called for NHS frontline staff with symptoms of the virus to be tested as a priority. A petition by junior doctor Rebecca McCauley said NHS staff are facing the “dilemma” of deciding to either take seven days off work – further contributing to staff shortages – or risking exposing their patients and colleagues to Covid-19.

Sir Vallance said as testing capacity ramps up, the next priority group will be key workers, such as NHS staff. “I think we need a big increase in testing,” he told the committee. “And that’s what I’m pushing very hard for.

“What you don’t want is everybody coming to the hospital to be tested, that’s the worst possible thing. The quicker we can get to something that looks like a true community-based test that people can do easily, the better.”

When pushed on a timescale for this, he couldn’t say for sure. “There is a lot of working going on at the moment … to select which test we should go for – and how that can be ramped up.”

That said, he said it’s “quite likely” the private sector will be involved in some capacity, “so we can get things out there fast on the community side.” His comments come as one Harley Street clinic claims to offer “the only test in the world” that can identify Covid-19 and differentiate between nine other viruses with the same symptoms. This will be unaccessible for many, though, costing £375.

As it stands, we can only wait for testing in the UK to be increased. In the meantime, those who have symptoms of coronavirus are told to stay at home and self-isolate. Use the NHS 111 online service to monitor symptoms and seek medical advice if they worsen.