Doctors in the UK are treating a suspected case of rabies, the Public Health Laboratory Service said.
The patient, who is described as being seriously ill, was bitten by a dog while travelling in the Philippines, where the disease is known to be carried by dogs.
Doctors are awaiting the results of tests to confirm the disease, a PHLS spokesperson said.
Cases of rabies are not common in the UK, the last indigenous case of infection being in 1902.
The patient, whose sex or identity is not being confirmed, is being treated at an unnamed London hospital.
Vaccines can be given to people who are at risk of contracting rabies and to those who are newly bitten by a dog.
Other than the vaccine, there is no other treatment for the disease, which is often fatal.
The PHLS spokesperson said: ‘‘Rabies affects the central nervous system and the brain. It is usually fatal, but those who do survive, often survive with disabilities.
‘‘The symptoms are anxiety, a headache and a fever, followed by a spasm of the swallowing muscles leading to ultimate paralysis.’’
There is no public health risk, however, as human to human transmission does not occur, the spokesperson added.