A young lab technician in France developed a rare and fatal brain disease after she was accidentally exposed to prions, the infectious proteins that cause “mad cow disease,” according to a new report of the case.

The accident happened in May 2010, when the technician was 24 years old and working in a prion research lab, according to the report, published Wednesday (July 1) in The New England Journal of Medicine. She worked with samples of brain tissue from mice that had been infected with a form of mad cow disease, formally known as bovine spongiform encephalopathy (BSE).

While she was using forceps to handle the samples, she accidentally stabbed her thumb through a double pair of latex gloves, enough to break the skin and cause bleeding, the report said.

More than seven years later, in November 2017, the woman began to experience a “burning pain” in her neck and right shoulder, which later spread to the right side of her body. One year later, in November 2018, doctors examined a sample of her cerebrospinal fluid (CSF), which appeared normal. But by January 2019, she began experiencing symptoms of depression, anxiousness, memory impairment and visual hallucinations. In March, samples of her CSF and blood tested positive for variant Creutzfeldt–Jakob disease (vCJD), a fatal brain condition that can take years to show up after exposure to “mad cow disease” prions. The woman died in June 2019, 19 months after her symptoms first appeared.

Only a few hundred cases of vCJD have ever been reported, and most were tied to consumption of contaminated beef (from cows infected with mad cow disease) in the United Kingdom in the 1980s and 1990s, Live Science previously reported. The disease results from prion proteins that fold abnormally, leading to lesions in a person’s brain. There is strong evidence that the prions that cause mad cow disease also caused the U.K. outbreak of vCJD in the 1980s and 1990s, according to the Centers for Disease Control and Prevention. (It’s important to note that “classic” Creutzfeldt-Jakob disease is a related but separate condition from vCJD. Classic CJD was first diagnosed in 1920, and can be inherited or occur sporadically, and is not linked to consumption of contaminated beef.) 

Since the woman was born around the start of the BSE cattle outbreak, it is possible that she could have contracted vCJD through consumption of contaminated beef, but this scenario is unlikely, according to the report authors, from Assistance Publique–Hôpitaux de Paris, the public hospital system in Paris. On average, vCJD takes about 10 years to show up after exposure to contaminated food, and the last two patients with vCJD in France and the U.K. died in 2013 and 2014, the report said.

So it’s possible that the woman developed the disease from exposure to lab materials contaminated with prions. Studies in animals have shown that injection into the skin is an effective route of transmission for these prions.

A patient in Italy also developed vCJD after exposure to BSE-infected brain tissue in a lab setting, and died in 2016, the report said.

“Such cases highlight the need for improvements in the prevention of transmission of variant CJD” that can affect humans in labs, the authors concluded.

The report does not say what safety measures were taken at the woman’s lab, or how she was treated after her initial exposure. However, in July 2019, the AFP reported that the family of the technician had filed a complaint for “manslaughter” against the National Institute for Agronomic Research (INRA), where the accident occurred. The complaint alleged that the woman had “not been trained in risk,” was not wearing “adequate safety equipment” and had no medical follow-up, AFP reported. In particular, the woman should have been wearing “cut-resistant gloves” rather than latex gloves; and the woman did not undergo decontamination procedures until “about 20 minutes” after being injured, the complaint said. INRA told AFP it is cooperating with health authorities in the investigation of the case and that it is committed to transparency.

Originally published on Live Science.  

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