In the 1970s, a quiet and terrifying pattern emerged in hospital maternity wards across the United States. Newborns were coming down with neonatal herpes simplex virus (HSV) infections, often with devastating consequences. For decades, the route of transmission baffled clinicians. The virus was not being passed from mother to child during birth in most of these cases. Something else was going on.
The man who cracked the case was Bernard Roizman, a University of Chicago virologist who had spent 20 years tearing apart the herpes simplex virus at the molecular level, mapping its genome and purifying its DNA when few believed it could be done. What he discovered would give medicine a brand new field, molecular epidemiology, and save countless infant lives.
Roizman, ScD, the Joseph Regenstein Distinguished Service Professor Emeritus at the University of Chicago, died on April 13, 2026 in Chicago at age 96. He reshaped virology from a descriptive science into a molecular one. But of all his achievements, the one that most powerfully illustrates his legacy may be the moment he followed a discovery out of the lab and into the hospital.
The Fingerprint
The insight that launched molecular epidemiology was elegant in its simplicity. Roizman and his team discovered that HSV gene sequences vary significantly among unrelated individuals but are virtually identical among related individuals infected with the virus. In other words, every strain of HSV carries a unique genetic signature, and that signature passes intact from one infected person to the next. These were, in effect, genetic fingerprints.
Today, the idea of using pathogen genetics to trace transmission is commonplace. We watched it happen in real time with SARS-CoV-2 during the COVID-19 pandemic. Genomic epidemiology is now a standard tool in public health. But when Roizman first described this phenomenon, it was revolutionary. He had given infectious disease investigators a way to follow a virus from one human host to another with forensic precision.
And he had a specific problem in mind for it.
The Maternity Ward Investigation
Roizman used his genetic fingerprinting technique to analyze HSV isolates from infected newborns in hospital maternity wards. What he found was disturbing. The viral strains causing illness in different infants were not the ones their mothers carried. The strains were identical to each other, suggesting a common source of transmission that was not maternal.
The culprit was the hospital staff. Roizman demonstrated that nurses were inadvertently carrying the virus between infants on their hands, transmitting HSV from one newborn to another simply by failing to wash their hands thoroughly between patient contacts.
His findings, published in the New England Journal of Medicine, led directly to changes in hospital infection control practices. Hand hygiene protocols were tightened. Staff education programs were implemented. The result was a dramatic reduction in nosocomial neonatal HSV infections, a concrete, measurable public health victory born directly from a piece of fundamental virology research.
It was not a drug Roizman developed or a vaccine he tested. It was something arguably harder and more important: a behavioral change driven by irrefutable molecular evidence. He had connected the bench to the bedside, and babies lived because of it.
The Architect of HSV Biology
The molecular epidemiology work, consequential as it was, represented only one chapter in a seven-decade career. Roizman was, first and foremost, the world’s foremost authority on herpes simplex virus itself, a complex DNA virus that infects the majority of the human population and establishes lifelong latency in the nervous system.
In the late 1950s, when Roizman entered the field, almost nothing was known about the molecular biology of HSV. He pioneered the methods for purifying HSV DNA and characterizing its unique structure. He went on to map the entire viral genome and define the functions of many of its 84 individual genes. He showed how the virus takes over host cellular machinery, a process fundamental to understanding both viral pathology and potential therapeutic intervention. Among the genes he characterized was one encoding an enzyme that became a target for the development of antiviral drugs.
“He had a very strong combination of intellectual curiosity and originality,” Glenn Randall, a former graduate student who is now a professor of microbiology at the University of Chicago, told The Lancet. “The measure of a great scientist is that they’re impactful outside of their own field. In Bernard’s case, this included molecular epidemiology, manipulating large genomes, and oncolytic therapy.”
Later in his career, Roizman turned the virus itself into a therapeutic tool. He engineered forms of HSV that had been stripped of their ability to damage the central nervous system while retaining their capacity to selectively infect and destroy cancer cells. These modified viruses became the basis for oncolytic virus therapy, a field of cancer treatment that is now being tested in clinical trials. Roizman also demonstrated that modified HSV could serve as a vector for delivering foreign genes into cells, advancing the prospects of gene therapy.
From Refugee to Regenstein Professor
Roizman’s path to scientific prominence was anything but predictable. He was born in Chisinau, Romania in 1929. His family fled the advancing armies of World War II across Eastern Europe, surviving displacement, deprivation, and near starvation before finally reaching the United States in 1947 aboard the SS Saturnia. They settled in Philadelphia.
Before he fell in love with science, he wanted to be a writer. “My aspirations came to an end when, in order to speed up my graduation from college, I took courses in microbiology,” he wrote in a 2015 autobiographical essay. “It was my second love at first sight, that of my wife preceded it.”
He married Betty in 1950, and the couple remained deeply devoted to each other throughout a 70-year marriage. He earned his bachelor’s and master’s degrees from Temple University before receiving a Doctor of Science degree from the Johns Hopkins School of Public Health in 1956. After serving on the faculty at Johns Hopkins and spending a year at the Pasteur Institute in Paris, he joined the University of Chicago in 1965 as an associate professor of microbiology. He would remain there for 52 years, becoming the Joseph Regenstein Distinguished Service Professor.
Over the course of his career, Roizman authored more than 650 peer-reviewed publications. He was elected to the National Academy of Sciences in 1979, the American Academy of Arts and Sciences, the National Academy of Medicine, and was a foreign member of the Chinese Academy of Engineering.
The Generations That Last
For all his publications and prizes, Roizman measured his legacy in people. He trained more than 100 graduate students and postdoctoral fellows, many of whom went on to establish their own research programs across the United States, Europe, and Asia. Beginning with his 60th birthday and continuing every five years after, his former students returned to the University of Chicago for scientific symposia in his honor.
“What lasts are not the scientific reports, but rather the generations of scientists whose education I may have influenced,” Roizman once said.
In 2021, the Roizmans endowed the Bernard and Betty Roizman Professorship at the University of Chicago. Shabaana Khader, PhD, is the first faculty member to hold the distinction. “Bernard was not only a towering figure in microbiology and virology, but he was also a devoted champion of the University of Chicago, where his passion for discovery and mentorship shaped generations of scientists,” Khader said.
Roizman retired in 2017 but never stopped working. He continued teaching and mentoring students in virology until the end of his life. “Although his physical health gradually became increasingly fragile, his passion for science never waned, and he remained intellectually engaged with his work and colleagues until near the end of his life,” said his niece, Leslie Fisher.
He is survived by his son Arthur. His wife Betty died in 2021, and his son Neils died of cancer in 2017.
Bernard Roizman leaves behind a transformed field of virology, a set of tools that have become the backbone of outbreak investigation worldwide, and generations of scientists who carry his approach to science forward. But his most tangible legacy may be this: thousands of babies who survived their first weeks of life because one virologist refused to stop at the bench, and followed the evidence all the way to the hospital ward.
References
1. Matt Wood, “Bernard Roizman, ScD, pioneering virologist, 1929-2026,” University of Chicago Biological Sciences Division, April 20, 2026. https://biologicalsciences.uchicago.edu/news/bernard-roizman-obituary
2. Jacqui Thornton, “Bernard Roizman (1929-2026),” The Lancet, Vol. 408, Issue 10552, p316, July 25, 2026. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(26)01439-X/fulltext
3. Bernard Roizman, “The Odyssey of a Virologist,” Annual Review of Virology, Vol. 2, 2015. https://www.annualreviews.org/content/journals/10.1146/annurev-virology-100114-054829