Times (London) May 21, 2004
Thousands carrying hidden CJD timebomb
By Nigel Hawkes, Health Editor
Concealed infection could be passed on by blood or surgery
BRITAIN is facing a variant-CJD timebomb with research
published today suggesting that thousands of people across
the country unknowingly carry the killer disease.
In the largest study into potential effects of vCJD,
scientists predict that up to 4,000 people may be infected
by the agent responsible for the degenerative brain disease,
which is the human form of mad cow disease.
Some may already be passing it on through blood
transfusions and contaminated surgical instruments, so that
the disease may continue to kill for decades. Last night
experts gave warning that the government-funded study,
published today in the Journal of Pathology, might even
have underestimated the threat.
Pathologists who examined more than 12,500 specimens of
tonsils and appendix removed in operations found evidence in
three cases of the prion protein responsible for vCJD.
If that proportion is repeated across the country, about
3,800 people would be carrying the infective agent — far
more than the 141 who have died of it so far. The samples
were anonymous, so it is impossible to identify the three
who tested positive.
Most came from people aged between 20 and 29, the peak age
for developing vCJD.
"I find these results very concerning," Professor John
Collinge, head of the Medical Research Council Prion Unit at
St Mary's Hospital, London, said. "Our experience is that
looking at appendix samples will underestimate the true
picture. In addition, no test is 100 per cent effective, and
you don't know at what stage in the incubation period the
test will be positive."
Professor James Ironside, senior pathologist at the National
CJD Surveillance Unit in Edinburgh, who took part in the
research, said: "There would seem to be more positives than
you would expect. That may be because of genetic differences
and susceptibility, but it may also be that you can have a
sub-clinical infection which never progresses to produce
symptoms — a ‘carrier state'.
"The findings do have to be taken seriously. Generally one
has to be cautious about interpreting these data, but they
may indicate that there are people who are not infected in
the normal way but could represent a source of infection."
When vCJD first appeared in 1996, estimates of the number
who might be infected ranged as high as 500,000. But as
the number of cases has risen only slowly, the
projections have fallen to somewhere between a few
hundred and a few thousand.
That people may be unwittingly carrying vCJD infection does
not mean that they will get the disease. But even if it
remains permanently in a sub-clinical state, there are
alarming implications for surgery and blood transfusions.
Carriers might pass on the infectious prion to those who
are more susceptible through contaminated instruments or
blood. Alternatively, the ultimate toll may rise higher
because only those most susceptible have so far developed
full symptoms.
People with a particular genetic pattern are most
susceptible to the disease and so far all the victims come
from this group. But others may get it after a longer
incubation period.
Dr David Hilton, of the Department of Histopatho- logy at
Derriford Hospital, Plymouth, who led the study, said:
"Our findings need to be interpreted with caution, but
cannot be discounted. There is still much to learn about
vCJD, and presence of the protein in these tissue samples
does not necessarily mean that those affected will go on
to develop vCJD."
Professor Collinge said that he thought the Government
should look again at using disposable surgical instruments
for operations that might involve a risk of transmission. A
recommendation for the use of such instruments introduced
in England was withdrawn about two years ago because of
safety fears.
The Department of Health said: "There is still much to learn
about vCJD and this study is important for future research.
The Department has put in place measures to reduce any risk
of possible transmission of the disease via blood products
and surgical instruments."
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