The Secretary-General of the World Health Organisation, Dr Tedros Adhanom Ghebreyesus, has told countries to “test, test, test” for the COVID-19 virus. But what is the reasoning behind this?

Well, there are two main types of testing, and they can both help the government and health authorities to get a better idea of where COVID-19 has spread, and where they need to focus their efforts to combat the transmission of the disease.

The first type of test is a PCR test – it detects genetic material within the virus, and can tell people whether they have COVID-19 right now. The UK is already using these, and has been seeking to boost its capacity to conduct PCR tests on a large scale.

Public Health England and the NHS have gone into overdrive. PHE has been mobilising its 12 regional labs to work on getting large numbers of PCR tests produced and get results back for those tests that are already being made. NHS Trusts have been setting up facilities since the end of February around the country to provide “drive through” COVID-19 tests. PHE is also trying to get private sector providers involved in the national effort.

This will still take a bit of time. PHE hopes to have increased their capacity to conduct tests to 25,000 per day by around 15 April. Rapidly increasing testing capacity would enable the authorities to test not only in hospitals and among severe cases, but also among frontline NHS staff and in the community more generally.

The trouble is, it is one thing to have capacity, and it is another to carry out tests. Public Health England has said that is expects to ramp up the capacity to about 10,000 test per day this week. But according to the Department for Health and Social Care, since 19 March around 5,000-6,000 tests per day have been carried out.

One thing that might help with this is a “remote” test, which Health Secretary Matt Hancock says he hopes will be in hospitals “within days”. At the moment tests have to be sent off to PHE labs where a result is usually provided in 24 hours. Remote tests would allow NHS staff to test and get results back on site and act quicker.

Then there is the second type of test – the “game changer” antibody test – which will be able to tell you if you have had the virus in the past and recovered.

The good news on this is that antibody testing is not a new technology. It is a similar model to that which is used for pregnancy tests, which is also an antibody test, although it works in a slightly different way. This means that, once PHE and the NHS are certain that the prototype antibody test they have in house can be rolled out, they can rapidly scale up numbers using existing factories in the country which are used to producing large numbers of these types of test – and quickly.

A final point is delivery – if and when enough remote tests become available for use outside of hospitals, they’ll need to be dispatched where they are needed most. The government is said to be in discussion with Amazon about how their supply networks can be used to rapidly roll out such tests as they become available.

At the moment, tests in the UK are a scarce resource and are being employed as such. Those who are severely ill and vulnerable in hospitals are currently being prioritised. Latest WHO data from 20 March shows that the UK had conducted 959.7 tests per million people in the population. Germany had conducted 2,023.3 and South Korea 6,148 per million people respectively.