It began with anxiety and depression. A few months later, hallucinations appeared.
Then the Texas man, in his 40s, couldn't feel or move the left side of his face.
He thought the symptoms were because of a recent car accident. But the psychiatric problems got worse. And some doctors thought the man might have bipolar disorder.
Eventually, he couldn't walk or speak. He was hospitalized. And about 18 months after symptoms began, the man died.
An autopsy confirmed what doctors had finally suspected: mad cow disease.*
The case, published Wednesday in the journal Emerging Infectious Diseases, is only the fourth one diagnosed in the U.S. In those previous cases, people caught the disease in another country.
Right away the man's diagnosis raised a new question: How did a rare disease linked to contaminated beef in the U.K. more than a decade ago get to a Texas man?
Back in the early '80s, British ranchers noticed some of their cows were dying of a strange neurological disease. The cows became aggressive. They couldn't walk.
Eventually, scientists figured out the culprit. A rogue protein formed large clumps in the brain and spinal cord. Over time, the clumps spread throughout the brain and damaged tissue.
Cows were catching the deadly protein from feed that contained ground-up brains of sheep and cows. Once ranchers stopped feeding their animals these organs, the disease almost vanished.
But figuring all that out took time. And from 1980 to 1996, the U.K. continued to export contaminated beef around the world. More than 200 people in 12 countries died from mad cow disease.
It can take more than a decade for mad cow disease to appear after a person is exposed to the proteins. But in every reported case, people had eaten beef in the U.K. or in a country known to have imported contaminated meat.
The source of the infection in Texas is less clear, says Dr. Atul Maheshwari, a neurologist at Baylor College of Medicine in Houston. Maheshwari was one of the doctors who took care of the patient with mad cow disease, and he led the study.
The patient had lived in the U.S. for 14 years before becoming sick. Maheshwari says he most likely didn't catch the disease here. The country has recorded only a handful of mad cow cases in cattle since it began testing in 2003. And the U.S. didn't import contaminated beef from the U.K.
So Maheshwari and his team started tracking down where their patient had lived decades earlier, when the U.K. was exporting dangerous meat.
The doctors narrowed down the source to three countries: Kuwait, Lebanon or Russia. None of them have reported any mad cow cases in people or had large outbreaks in cattle. But Kuwait was importing a large quantity of beef, per capita, from the U.K. while the man was living there.
"The risk of infection would have been highest in our patient when he lived in Kuwait," Maheshwari says. "But we do not think," he stresses, "that [the new case in Texas] means it is more risky now to eat beef today in Kuwait, Lebanon or Russia."
Since 2012, there have been only four cases of mad cow disease detected in people around the world, including the one in Texas. And the U.K. has improved its tracking and monitoring of cattle.
But Maheshwari hopes the case will have a few repercussions. First off, he hopes doctors and nurses will be more aware that mad cow disease, although extremely rare, can occur, even in people in the U.S.
And the case will help remind health officials around the world that watching out for mad cow disease is still critical. It can crop up in new places, at any time.
"Since 1996, there have not been any known large epidemics in cows," Maheshwari says. "But the U.S. has been monitoring the beef industry to make sure another epidemic does not occur."
*Note: Mad cow disease is also known as variant Creutzfeldt-Jakob disease because it is related to another disease, called sporadic Creutzfeldt-Jakob disease. Caused by a human protein, sCJD is more common than mad cow disease but still quite rare, with about 1 case per 1 million people each year.