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By Patricia Reaney on January 12, 2005
(Excerpt - for complete article please
visit Reuters.co.uk)
LONDON (Reuters) - A major epidemic of
the human form of mad cow disease is unlikely, scientists
say.
Estimates of how many people are likely
to develop the fatal brain disease from eating meat
contaminated with bovine spongiform encephalopathy (BSE)
have varied widely.
But researchers at Imperial College London
said on Wednesday they believed only about 70 future
cases of variant Creutzfeldt-Jakob disease (vCJD) would
be diagnosed in the country.
"We think that the epidemic will
be quite small in terms of cases that have arisen from
consumption of beef," said epidemiologist Dr Azra
Ghani.
The calculations are based on tonsil and
appendix samples, where evidence of infection is most
evident, taken from 12,764 people. Three samples tested
positive but only one matched tissue taken from a person
with the disease.
The pool of infected people could be up
to 3,800 people, but only a small number of them would
develop the illness.
"One reason for the discrepancy between
the high estimated number of positive tests and low
number of actual recorded clinical cases could be that
many infected individuals do not go on to develop clinical
disease in their lifetime," Ghani said.
Because of the long incubation period,
which scientists estimate could be from 10 to 20 years,
it has been difficult to predict how many cases of vCJD
there will be.
Up to November 1 last year, 146 people
had died from definitive or probable vCJD in Britain,
the Department of Health says.
Ghani and her team reported their findings
in Wednesday's Journal of the Royal Society Interface.
Their estimate only refers to people infected through
BSE-infected beef.
"Although our results indicate there
is little chance of large numbers of vCJD infections
from primary transmission, we have not taken into account
the possibility of additional cases infected by blood
transfusion. This could result in more clinical cases
emerging at a later date," she said.
Two suspected cases of vCJD via blood
transfusion have been reported so far. The government
announced what was thought to be the world's first case
in December 2003 after a patient died several years
after receiving blood from a donor later found to have
had the illness.
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