The main challenges facing Britain and the wider world are containment, finding everyone infected and stopping the spread, and the treatment of very ill patients, which could easily overwhelm hospitals in any country, however well-developed the health system.

Finding people who have been infected is extremely challenging, but it is essential for containment. We are lucky we do have fairly rapid tests available, based on detecting the virus in patient blood samples, for example. However, these will only work when patient is quite sick. After people get better, or if they have mild infection, the virus can’t be detected.

The current rapid tests are based on detecting the nucleic acid of the virus by measuring RNA. This is the genetic ‘code’ of the virus. When the level of the virus drops in, a patient doesn’t have very much viral RNA. This is good for the patient but makes the virus almost undetectable.