A patient is being assessed for possible symptoms of Ebola at the Royal Cornwall Hospital in Truro.
The person is being kept in isolation and the result will be known in around 24 hours.
The patient had recently been in a high-risk Ebola area, although the exact location has not been revealed.
The tests are thought to be precautionary – more than 100 patients have tested negative in similar circumstances over the last few months.
Symptoms of Ebola are very similar to other tropical diseases, such as malaria.
It comes as the first person to be diagnosed with Ebola in the UK – a Scottish nurse – arrives in London for specialist medical care.
In a joint statement, the hospital and Public Health England said: “A patient has been admitted to Royal Cornwall Hospital and is currently undergoing a series of tests – one of which is for Ebola.
“We do not expect the results to be known for at least 24 hours and in the meantime the patient is being looked after in isolation, following nationally agreed guidelines and protocols to protect the health of our staff and other patients.
“Royal Cornwall Hospitals NHS Trust has been following national guidance around Ebola and made plans in line with advice from Public Health England and NHS England.”