Jordi Casals-Ariet, an epidemiologist and virologist, was hailed by scientists around the world when he discovered the virus that causes Lassa fever. He was nearly killed by the disease in 1969 while working with the virus in his Yale laboratory. In a high-stakes gamble and with no known treatment, his doctors decided to transfuse him with blood from a nurse who had survived Lassa fever. The blood saved his life.

But colleagues say that Dr Casals' contributions are far greater than his discovery of the Lassa fever virus. “He did a yeoman's work in establishing useful methods of classifying viruses,” said Dr Gregory Tignor, professor emeritus at Yale, who worked with Dr Casals.

Little was known about many viruses when Dr Casals started his work at Yale. “Everybody has forgotten how bad it was back then,” said Dr Tignor. “People didn't know what was causing encephalitis. We had no way of telling the difference between rabies encephalitis, polio encephalitis, or other causes of encephalitis. But Jordi found ways, using antigens and antibodies, to figure it out. His work was so meticulous that to this day nobody has changed his classifications because they have all held up.”

Charles H Calisher, professor of microbiology at Colorado State University, said that Dr Casals defined the field of viral taxonomy for thousands of viruses that affected humans, livestock, plants, and bacteria. He served on many scientific commissions on polio, and mosquito and tick-borne viruses, and worked with scientists in Japan on the Japanese encephalitis virus and the former Soviet Union on haemorrhagic fever viruses.​viruses.

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Credit: YALE UNIVERSITY

Jordi Casals-Ariet was born in Viladrau, Girona, Spain, in 1911. He came to the United States after graduating from medical school in Barcelona. He joined the Rockefeller Institute for Medical Research in 1936 after two years in the department of pathology at Cornell University Medical College. When his unit at the Rockefeller Institute moved to Yale in 1964, Dr Casals transferred with the unit and remained there until his retirement in 1981.

That Dr Casals' work has held up over time is something his wife, Ellen Evelyn Casals-Ariet, says was due to his refusal to accept a single test result as proof of anything. “He'd repeat a successful test over and over and over again,” said Ms Casals-Ariet. “Jordi was disturbed by people who didn't repeat tests. Now we see just one test being used to promote something. What's good one day is bad the next. It causes the public to despair. Jordi was upset by researchers who didn't repeat their tests. He said they were too anxious to get published or be first with a discovery.”

Several close colleagues of Dr Casals said his professional ethics impressed them as much as his scientific methods. “People who worked in that day and age worked at great risk to themselves personally. Many investigators died from yellow fever and some from polio. But they did it because of the benefit for mankind,” said Dr Tignor. “Today, our research is centered on what's going on in America and to hell with the rest of the world. If you want to study a disease you have to study diseases of rich old white men because they are the ones who sit in Congress. But Jordi studied diseases that affected people who were dying in Africa.”

Ms Casals-Ariet said that in later years “Jordi complained that non-commercial funding was harder and harder to find. It was a constant problem. That's why he liked working for the Rockefeller Institute. They were free to pursue science for the sake of science and not because some big corporation could make money from it.”

Dr Casals served as a consultant to the Walter Reed Army Institute of Research, the World Health Organization, the US National Institutes of Health, and the International Committee on Taxonomy of Viruses. In 1969 he received the Richard M Taylor Award, given by the American Committee on Arthropod-Borne Viruses once every three years to “a person who has made outstanding contributions to arbovirology throughout his or her career.” He also received the Kimble Methodology Award from the American Public Health Association.

Ms Casals-Ariet said that when people heard her name they would often say, “Casals? Casals! Are you related to Pablo Casals [the cellist]?” But one day, to her great pleasure, a visiting doctor from Europe, exclaimed, “Casals? Casals! Are you related to Jordi Casals?”

He leaves a wife, Evelyn “Lyn,” and a daughter.

Jordi Casals-Ariet, virologist and epidemiologist Yale University, New Haven, Connecticut, United States (b Viladrau, Spain, 1911; q University of Barcelona 1934), d 10 February 2004.