"Blood screening technology may be able to diagnose infections before symptoms emerge".
"Eating beef from an animal infected with mad cow disease can lead to an untreatable condition that attacks the brain and is universally fatal, but symptoms can take decades to emerge. Thankfully, a new blood-screening technology can spot the condition, known as variant Creutzfeldt-Jakob disease, with 100 percent accuracy, perhaps years before it attacks.
Misfolded proteins called prions cause both mad cow and variant Creutzfeldt-Jakob disease. Once they invade the brain, they begin recruiting normal proteins and forcing them to adopt the same abnormal shape. The prions and the blighted proteins clump together forming increasingly large aggregate deposits that wreak havoc on the brain and invariably lead to death. The disease, however, has a long incubation period. 'In the case of humans, the estimation goes from several years to a few decades,' says Claudio Soto, a neurologist at McGovern Medical School at UTHealth in Houston. 'So it could be that you're exposed one day and then, 40 years after, you develop the disease.'
In the interim, the prions hang out in non-brain tissues such as the appendix and tonsils, and because they do not cause symptoms, the infected person becomes a silent carrier. Perhaps the worst outbreak of variant Creutzfeldt-Jakob disease occurred in the United Kingdom during the 1980s and 1990s, when large swaths of the population were exposed to beef contaminated with mad cow disease. Since then, there have been 277 cases in the U.K. and an epidemiological study published in 2013 estimates that another 1 in 2,000 people there, about 30,000 in total, are silent carriers. While it is not clear how many of these people will go on to develop the disease, blood donations from silent carriers could jeopardize the country’s blood supply, according to Soto. The new screening test stands to alleviate the uncertainty, however."