Developments in molecular diagnostics led to a swift diagnosis of Lassa fever in a 52-year-old British aid worker in March. Treatment has to be within six days of onset if the prognosis is to be good, so speed of diagnosis is vital.

Laboratory confirmation is necessary because Lassa fever presents with a range of non-specific symptoms such as flu-like illness, vomiting and diarrhoea, progressing to haemorrhage and multi-system failure.

The aid worker had been in Sierra Leone when he became ill with a fever on 21 February. He was transferred to the UK and admitted to the Hospital for Tropical Diseases, University College London Hospitals on 7 March.

Differential diagnoses included malaria, typhus and dengue.

At midday on 10 March a test called the polymerase chain reaction was used for the first time to diagnose Lassa fever, giving a result within eight hours instead of the three days taken by traditional tests. This rapid molecular diagnosis meant that clinicians could begin specific antiviral treatment within an hour of knowing the diagnosis and it meant that infection-control procedures were put in place not only in the UK but in Sierra Leone, too. Unfortunately, the patient did not survive and died on 23 March.