Thought this might interest you prion-watchers. From the ProMED
group.
peace
misha
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CJD, NEW VAR., PROJECTIONS - UK
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Date: Mon, 7 Dec 1998 15:13:12 -0500
From: Martin Hugh-Jones
Source: The Times, December 7 1998, Michael Hornsby, edited]
Two scientists at City University in London say that fewer than 100
people are likely to die from nvCJD [the putative human form of BSE]
and an epidemic can be ruled out. In addition Professor Thomas and
Martin Newby, Professor of Statistical Science, believe that as few as
four, and no more than 15, lives will be saved by the billions of
pounds spent by the UK government since 1996 on such BSE
counter-measures as slaughtering all cattle over 30 months old.
They claim to have reached this conclusion through tried and tested
risk analysis methods. "What we are saying is that there is not an
epidemic and that it has been obvious for the past 2.5 years that
there is not going to be an epidemic," Philip Thomas, visiting
Professor in the Department of Electrical, Electronic and Information
Engineering, said.
The scientists' findings have been submitted as evidence to the BSE
inquiry. A more detailed report on their research will be published
next month in the British Food Journal. Their study is based on the 23
people who had died of new-variant Creutzfeldt-Jakob disease by the
end of 1997.
Since then the disease has claimed nine more victims, a death rate
fully in line with their predictions, they say.
The most likely number of deaths over the whole course of the disease
is 87, they estimate, based on the time between infection and death
averaging 6.5 to eight years. The scientists expect the annual
incidence of new cases of new-variant CJD to reach a peak of 16 next
year and then to start falling, with no more occurring after 2006.
Even if the average incubation period were to turn out to be nearer
20 years, they say the number of deaths would not be more than 330.
The forecast death toll of 87 assumes that the ban introduced in 1989
on brain, spinal cord and other potentially infected cattle parts has
been 70 per cent effective in preventing such material from entering
the human food chain. Had the ban been 100 per cent effective, they
calculate, no more than 26 people would have died over the course of
the disease.
But even without any ban, the number of victims would probably not
have exceeded 109.
Their prognosis is in striking contrast with the far more cautious
view of the Spongiform Encephalopathy Advisory Committee, the panel of
scientists advising the Government. Peter Smith, a SEAC member and
Professor of Tropical Epidemiology at the London School of Hygiene and
Tropical Medicine, said: "I fear they are going much further than the
data allows at this stage."
***
[I copied the above to Bob laBudde, who replied as follows - Mod.MHJ]
Date: Mon, 07 Dec 1998 15:42:31 -0500
From: "Robert A. LaBudde"
The conclusions reached in the research mentioned in this article are
similar to those I found in my note "Constant force of mortality
observed in the new variant of Creutzfeldt-Jakob disease in the UK",
published in International Food Safety News (1998) 2:2-3.
However, where I found a constant number (6.7) of cases per year based
on date of onset of symptoms, these scientists seem to have included a
model based on the distribution of incubation periods (typically a
gamma distribution is used).
I personally do not believe that a sufficiency of data yet exists to
distinguish between a constant background rate of cases (which I
found) and a very slowly changing case rate. In any event, in my
analysis I found no evidence of any change in case rate from the
constant value. If incubation periods were a significant issue, the
hazard rate would have curved, rather than been straight.
In addition, there has been considerable discussion on the BSE-L
listserve concerning the possibility of dichotomous susceptible
populations, resulting in conceivably time-separated case rate
distributions, with the calamity yet to be initiated in future years.
Personally, I believe the current case rate distribution is the
largest isolated epidemic to be experienced, with the less susceptible
populations generating only possibly aggravated geriatric statistics.
In defense of the British government, I feel it would have been
extremely imprudent to allow beef from mature animals to reach the
human food supply, given that BSE cases are still occurring in cattle
and nvCJD cases were discovered in humans.
Remember also, the cost impact of subclinical cases in humans has yet
to be assessed.
- ---
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
Michele Gale-Sinex, communications manager
Center for Integrated Ag Systems
UW-Madison College of Ag and Life Sciences
Voice: (608) 262-8018 FAX: (608) 265-3020
http://www.wisc.edu/cias/
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Lenguage is, that we may mis-unda-stend
each udda." --Krazy Kat
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