A grandmother is critically ill in hospital after she was reportedly bitten by a dog while on holiday in India.
The identity of the woman, who is reported to be in her 50s and from Greater London, has not been disclosed.
But the Hospital for Tropical Diseases in London has confirmed the patient has rabies and is critically ill in hospital.
Rabies is potentially fatal but officials have stressed there is no risk to the public.
Sky News reporter Enda Brady said: "The hospital is saying very little but newspaper reports say she had been on holiday to India with her husband about nine weeks ago and that she was bitten by a puppy.
"She only felt unwell about 10 days ago. She went to her GP who initially sent her home. The next day she went to an A&E department in Dartford, Kent, and they too sent her home.
"Twenty-four hours later she returned to the same hospital feeling more unwell and at that stage she was referred to a hospital in Woolwich, south London, where they felt her symptoms were possibly compatible to rabies.
"They then transferred her to the Hospital for Tropical Diseases where rabies was confirmed and where she remains critically ill."
Rabies experts at the Health Protection Agency say the disease is "extremely rare" in the UK.
Only four cases of human rabies acquired from dogs have been identified since 2000, all from animals abroad, the agency says.
Dr Brian McCloskey, director of the HPA for London, said: "Despite there being tens of thousands of rabies cases each year worldwide, there have been no documented laboratory confirmed cases of human-to-human spread.
"Therefore the risk to other humans or animals from a patient with rabies is considered negligible.
"However, to take every possible precaution, family members and healthcare staff who had close contact with the patient since they became unwell - which is when they are infectious - have been assessed and offered vaccination if appropriate."
Rabies is usually transferred through saliva from the bite of an infected animal with dogs being the most common transmitter of the disease to humans.
There are estimated to be more than 55,000 human fatalities every year, with most cases in developing countries.
The HPA says it is "essential to get health advice if you are travelling to countries where rabies is common or if you know you will be working with animals".