- January 08, 2026
- By Fid Thompson
This year’s flu season is turning out to be the worst in decades, with at least 7.5 million cases and thousands of deaths so far, according to the Centers for Disease Control and Prevention. As a new variant known as subclade K spreads misery nationwide, a new University of Maryland study offers clues about escaping it.
The short version: Avoid getting coughed on—or coughing on people. Wear a mask if that’s not practical. Breathe clean air and stick to well-ventilated spaces.
Those findings, out Thursday in PLOS Pathogens, resulted from the first clinical trial in a controlled environment to investigate exactly how the flu spreads through the air between naturally infected people (versus those deliberately infected in a lab) and uninfected people.
Researchers from the School of Public Health and A. James Clark School of Engineering in College Park and from the University of Maryland School of Medicine in Baltimore wanted to find out how the flu spreads, so they recruited college students already sick with the flu to temporarily move into a sealed-off floor of a historic Baltimore hotel with healthy middle-aged adult volunteers. The result? No one caught the flu.
“At this time of year, it seems like everyone is catching the flu virus. And yet our study showed no transmission. What does this say about how flu spreads and how to stop outbreaks?” said Dr. Donald Milton, professor at SPH’s Department of Global, Environmental and Occupational Health and a global infectious disease aerobiology expert who was among the first to identify how to stop the spread of COVID-19.
“Our data suggests key things that increase the likelihood of flu transmission; coughing is a major one,” said Jianyu Lai, a postdoctoral research scientist in Milton’s lab who led data analysis and report writing for the team.
The students with the flu had a lot of virus in their noses, said Lai, but they did not cough much at all, so only small amounts of virus got expelled into the air.
“The other important factor is ventilation and air movement. The air in our study room was continually mixed rapidly by a heater and dehumidifier and so the small amounts of virus in the air were diluted,” Lai said.
Most researchers think airborne transmission is a major factor in the spread of this common disease, but updating international infection-control guidelines requires evidence from randomized clinical trials such as this one, Milton said. The team’s ongoing research aims to show the extent of flu transmission by airborne inhalation and exactly how that airborne transmission happens.
The lack of transmission in this study offers important clues to how we can protect ourselves from the flu this year.
“Being up close, face-to-face with other people indoors where the air isn’t moving much seems to be the most risky thing, and it’s something we all tend to do a lot,” Milton said. “Our results suggest that portable air purifiers that stir up the air as well as clean it could be a big help. But if you are really close and someone is coughing, the best way to stay safe is to wear a mask, especially the N95.”
The team measured airborne transmission between five people with confirmed influenza virus with symptoms and a group of 11 healthy volunteers across two cohorts at the Baltimore hotel in 2023 and 2024. Milton and colleagues had used a similar quarantine set-up in an earlier study and “exhaled breath” testing also was included in several other of his pioneering studies.
During the hotel study, participants’ daily activities simulated different ways that people gather and interact, including conversational ice-breakers, physical activities like yoga, stretching or dancing. Infected people handled objects such as a pen, tablet computer and a microphone, before passing the objects among the whole group.
Researchers tracked a wide range of parameters, including participant symptom monitoring, daily nasal swabs and saliva samples and blood collection to test for antibodies. The study measured the viral exposure in volunteers’ breathing area as well as what was in the ambient air of the activity room. Participants’ exhaled breath was also measured daily in the Gesundheit II machine, invented by Milton and colleagues at Harvard T.H. Chan School of Public Health.
The study included researchers at UMD’s interdisciplinary Public Health Aerobiology Lab—Kristen Coleman, Yi Esparza, Filbert Hong, Isabel Sierra Maldonado, Kathleen McPhaul and S.H. Sheldon Tai—as well as colleagues from UMD’s Department of Mechanical Engineering, the University of Maryland School of Medicine, Icahn School of Medicine at Mount Sinai in New York, the University of Hong Kong and the University of Michigan.
At a Baltimore hotel, researchers and students from Milton's lab test technology to track the movements of flu study participants by playing a dancing game.