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.
Rabies almost always leads to death once symptoms have begun. It has the highest death rate of any type of viral infection and, to date, there has been only one reported case of someone surviving a rabies infection.
More than 55,000 people are estimated to die from the disease every year, with most cases occurring in developing countries, particularly in south and south-east Asia.
University College London Hospitals NHS Foundation Trust said: “We regret to announce that a patient being treated for rabies by the Hospital for Tropical Diseases and colleagues at University College Hospital died over the weekend.”
An investigation has been launched into how the woman was reportedly turned away twice by doctors at Darent Valley Hospital in Dartford, Kent, before she was finally diagnosed.
A spokesman for Darent Valley Hospital last week said: “The hospital responded to the information supplied by the patient at the time.
“Although there are no cases of rabies being passed through human-to-human contact, the five members of staff that came into close contact with the patient are being vaccinated as a precautionary measure.”
On Friday, disease control experts announced a second possible British case of rabies was being investigated, in the case of a patient from Leeds.
The patient sought medical attention following a dog bite abroad, the Health Protection Agency (HPA) said. The patient had “no links” to the confirmed case in London.
Dr Ron Behrens, of the London School of Hygiene and Tropical Medicine, said the prognosis was “bleak” for people infected with rabies, with only one or two cases known to have survived rabies encephalitis – the disease once it reaches the brain.
He said symptoms resulted from inflammation of the brain from the virus. “In the early stages, the symptoms are mild headaches, some anaesthetic feeling around the site of a bite and fever. There is often confusion and delirium.”
A unique symptom is a fear of water, which means patients cannot drink or swallow.
If bitten by a rabid dog, there is roughly 24 hours where treatment with an antibody can prevent the virus entering the nervous system, Dr Behrens said.