There are three “classical” forms of CJD, including “Sporadic CJD” (most common and of unknown cause), “Acquired CJD” (rare and comes from infected human tissue or growth hormone), and “Familial CJD” (passed on through families through mutations in the prion protein gene “PRNP“). The PRNP gene has been identified and sequenced, and family members of those with this form of the disease can be tested for the gene (and are acceptable blood donors if negative).
Variant CJD (vCJD), unlike the three classical forms of CJD, is a really big deal for blood banks! vCJD was first seen in the United Kingdom, and most likely came from a similar disease in cows (bovine spongiform encephalopathy, or “mad cow disease”). vCJD may have a very long incubation period (up to fifteen years), and tends to cause earlier fatality and younger age onset than classical CJD types. vCJD has been clearly shown to be transmitted via transfusion. To prevent vCJD transmission, U.S. blood donors who lived in the UK for more than 3 months between 1980 and 1996, those who lived in the rest of Europe for more than 5 years since 1980, or those who received a transfusion in Europe since 1980 are permanently deferred from blood donation in the US.
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