A "second wave" of the incurable human form of mad cow disease could hit Britain causing greater numbers of deaths, a new study has warned.
The full extent of the outbreak of the deadly variant Creutzfeldt-Jakob disease (vCJD) has not yet been realised, scientists believe.
The next wave could take the form of a "tidal wave or an imperceptible ripple", they warn.
To date 167 people have died from vCJD in Britain since it was first diagnosed in the mid-1990s.
But scientists warn that thousands of people could still go on to develop the disease because of the length of time it can remain in the body with no symptoms.
Earlier this year scientists warned that up to one in 4,000 people in Britain could carry the infection, although the vast majority of them would never go on to develop the full blown disease.
The results of the new study show that the disease is affected by genetic factors in patients.
The individual make-up of a patient could increase the amount of time that the infection, commonly contracted through eating infected meat or though a blood transfusion, lies low before symptoms develop, they warn.
The research shows that it is an individual's DNA which controls if and when the disease will manifest itself.
The study also identifies some but not all of the common patterns which can signpost if a person is likely to go on to develop the incurable disease.
The research, the findings of which are published in the journal Lancet Neurology, analysed DNA samples from all the British patients who have died from the disease and compared them with samples from healthy blood donors.