London Ambulance staff members are seen with vehicles in the car park at the ExCeL London exhibition centre in London on April 1, 2020, which has been transformed into the NHS Nightingale Hospital to help with the novel coronavirus COVID-19 pandemic. DANIEL LEAL-OLIVAS

U.K. Prime Minister Boris Johnson has been forced to defend the lack of widespread coronavirus testing for frontline health professionals — a situation that has attracted widespread criticism from the public. Making an online address on Twitter Wednesday, Johnson said testing was the key to solving the epidemic in the U.K., as it was revealed that only 2,000 frontline National Health Service (NHS) workers had been tested for the virus, out of around 500,000 NHS staff. Tweet Johnson, who is himself self-isolating after testing positive for the virus, said that testing would be ramped up amid an outpouring of criticism from NHS workers, opposition parties and the media about the lack of testing. 'We're also massively increasing testing," Johnson said Wednesday. "This is the way through. This is how we will unlock the coronavirus puzzle. This is how we will defeat it in the end." There are now 29,865 confirmed cases of coronavirus in the U.K. and 2,357 people have died from the virus, according to data compiled by Johns Hopkins University. Government data released Wednesday showed that the U.K. had registered its biggest daily increase in deaths, of 563 people, in the previous 24 hours.

The two tests

There are two tests for coronavirus: one tests for antigens, which are produced by the body in response to a coronavirus infection and show if an individual has the virus; the other, an antibody test, shows whether an individual has been exposed to the virus, and has developed immunity to it. The U.K. has been slow to implement widespread antigen testing as only a small number of U.K. laboratories have been enabled to carry out these tests. The Department of Health said yesterday that testing capacity for inpatients stands at 12,799 in England, with just over 10,000 tests being carried out Tuesday. Tweet By contrast, in countries like Germany and South Korea, mass antigen testing has been a key strategy in their fight against the coronavirus outbreak, and appears to have kept the death rate relatively low. Germany, which has 67,377 confirmed cases of the virus but only 732 deaths, is estimated to be carrying out around 500,000 antigen tests a week. The U.K. has only been testing very symptomatic cases, unlike Germany.

Antibody tests for the frontline

So far, testing has been constrained to antigen tests that see whether an individual has the virus. However, antibody testing is a key issue in the U.K. right now, as thousands of healthcare professionals are self-isolating at home because they — or their family members — have shown symptoms, but it is unknown whether or not they have the coronavirus. On Wednesday, Johnson said the government would "massively" ramp-up antibody testing as this test is seen as crucial to determining who is no longer vulnerable to being infected or contagious themselves, and is able to return to work. Health Minister Matt Hancock said last week that the government had ordered 3.5 million antibody tests. Neil Ferguson, a professor of mathematical biology at Imperial College London, whose studies are informing U.K. government policy towards the pandemic, said on Monday that antibody tests were in the final stages of validation and would hopefully be ready "in days rather than weeks."

Scathing response