CJD belongs to a group of neurological diseases
known as transmissible spongiform
encephalopathies (TSEs). TSE diseases in humans are
very rare but fatal.
CJD is a slow degenerative
human disease of the central nervous system. It is
classified as a transmissible spongiform
encephalopathy because of the characteristic spongy
degeneration of the brain that occurs as the disease
CJD occurs sporadically worldwide at a
rate of one case per 1 million people per year.
What is variant Creutzfeldt-Jakob disease
Variant Creutzfeldt-Jakob disease (vCJD) is another
rare and fatal human neurologic disease that falls
into the category of transmissible spongiform encephalopathies (TSEs).
disease, vCJD causes a spongy degeneration of
the brain. vCJD is a new disease, which was first described in March 1996.
How does vCJD differ from CJD?
In contrast to the classic form of CJD, the new variant or
variant form (vCJD) in the United Kingdom and
France affects younger persons (average age at onset is
28 years), and has different clinical features from
People with vCJD begin with serious
psychiatric problems or problems with their senses
(ears, eyes or smell), this first set of symptoms is
followed weeks or months later by poor muscle
coordination, problems with muscle spasms, and
mental confusion; these patients also have abnormal
The illness lasts for at
least 6 months, but most people die approximately 13 months after their symptoms begin. When patients'
brains are examined by autopsy, there are clear
changes in brain tissue structure including many "spongiform" or open spongy-looking areas,
abnormal spots of prion protein called plaques, and
other areas with much prion protein accumulation.
Exactly how does this newly recognized
variant of CJD differ from classical CJD?
In 1996 the Spongiform Encephalopathy Advisory
Committee (SEAC) in the UK announced the
identification of 10 cases of variant CJD (vCJD,
Lancet, 1996, 347:921-25).
The following features
describe how vCJD cases differ from the sporadic or
classical form of CJD:
The affected individuals were much younger
than the classical CJD patient. Typically, CJD
patients are over 63 years old. The average
patient with vCJD is 28 years old; patients
ranged from 12 - 52 years old.
The course of vCJD averaged 13 months.
Classical CJD cases average a six month duration.
In the vCJD cases, electroencephalographic (EEG)
electrical activity in the brain was not typical of
Although changes in brain tissue structure of
patients with vCJD were recognizable as CJD,
the pattern was different from classical CJD, with
large aggregates of prion protein plaques often
surrounded by vacuoles.
How did people get this new variant of CJD?
On March 20, 1996 a statement from the Spongiform
Encephalopathy Advisory Committee (SEAC) in the
United Kingdom indicated concern that before
November 1989, when inclusion of certain cow and
sheep by-products in human food was banned, the
BSE agent may have been transmitted to people
through contaminated food products.
The SEAC said
that food might account for the 10 vCJD cases
described in April, 1996 in the medical literature
The specific foods, if any,
that may be associated with the transmission of this
agent from cattle to humans are unknown. However,
the SEAC has indicated that milk and milk products
are unlikely to pose any risk for human exposure to
the BSE agent.
What is the evidence directly linking this
newly recognized variant of CJD to BSE
There is strong epidemiologic and laboratory
evidence suggesting that new variant CJD (vCJD)
and BSE are caused by the same infectious agent.
instance, there have been no confirmed cases of
vCJD in other geographic areas where there have
been no BSE cases. In addition, the time interval or "incubation period" between the most likely period
for the initial exposure of the population to
potentially BSE-contaminated food (1984-1986) and
onset of initial vCJD cases (1994-1996), about 10
years, is similar to the known time intervals between
exposure to the classical CJD agent and the
development of CJD.
An experimental study reported in June 1996
showed that three cynmologus macaque monkeys
that were injected with brain tissue from cattle with
BSE later developed symptoms and changes in brain
tissue that were strikingly similar to vCJD (Nature
Another study published in 1996
showed that prions obtained from 10 vCJD patients
and BSE-infected animals had molecular
characteristics that were similar to each other but
that distinct from prions obtained from patients with
classical CJD (Nature 1996;383:685-90).
intermediate results of an ongoing experimental
study involving injection of a panel of mice (Nature 1997;389:498-501). A recent study using transgenic
mice (PNAS 1999;96:15137-15242) supports the
hypothesis that the BSE agent from cattle causes
How many cases of variant CJD have
Cases of variant CJD are very rare, and most have
occurred in the United Kingdom.
information (October 2, 2000) issued by the
Department of Health, United Kingdom
(www.dohh.govv.uk/cjd/) indicates that there have been 73 confirmed cases of vCJD in the United Kingdom. These cases have all been diagnosed since 1995.
France has reported two cases.
The Republic of Ireland reported one case in 1999.
No cases have
been recognized in other European countries, or in
the United States.
Could anyone in Europe diagnosed with the
newly recognized variant of CJD (vCJD) have
acquired this from vaccines?
No evidence exists that any case of vCJD has
resulted from administration of a vaccine, and no
cases of vCJD has been reported in the U.S.
UK, the majority of cases of vCJD were born before
1980, and it is very unlikely that they received
vaccines contaminated with the BSE agent (Vaccine
Surveillance of vCJD in the UK has
identified three "risk factors," or characteristics
common to most if not all of the people who had
Residence in the UK
evidence to date suggests that these cases of vCJD acquired the disease from eating beef products
containing the BSE agent after 1980.
As of October,
2000 there have been 76 confirmed cased of vCJD.
Of these, 73 have occurred in the UK.
A case of vCJD
was reported in the Republic of Ireland in June 1999,
in a person who had been a UK resident from 1989
Two cases of vCJD have been diagnosed in
France, one in 1996 and the other in 1999. Neither of
these people had lived or traveled in the UK.
However, according to data published by the UK
(HM Customs and Excise), France was a leading
European importer of bovine products during the
period 1980-1996. No other cases of bovine products
during the period 1980-1996.