Study: How can we stop the spread of flu?

In a tough flu season, new research on airborne flu transmission gives insight on better outbreak control

University of Maryland

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Dr. Donald Milton sits in front of the Gesundheit II machine, invented by Milton and colleagues at Harvard T.H. Chan School of Public Health.

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Credit: UMD

COLLEGE PARK, Md. – This year’s flu season is turning out to be brutal. As a new variant known as subclade K spreads rapidly, a study out today offers clues as to how to avoid the annual sickness. 

Researchers from University of Maryland Schools of Public Health and Engineering in College Park and the School of Medicine in Baltimore wanted to find out how the flu spreads, so they put college students already sick with the flu into a hotel room 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.

The study, out today in PLOS Pathogens, is the first clinical trial in a controlled environment to investigate exactly how the flu spreads through the air between naturally infected people (rather than people deliberately infected in a lab) and uninfected people. Milton and his colleague Dr. Jianyu Lai have some ideas about why none of the healthy volunteers contracted the flu. 

“Our data suggests key things that increase the likelihood of flu transmission – coughing is a major one,” said Dr. Jianyu Lai, post-doctoral research scientist, who led data analysis and report writing for the  team. 

The students with the flu had a lot of virus in their noses, says 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. 

Lai adds that middle-aged adults are usually less susceptible to influenza than younger adults, another likely factor in the lack of any flu cases. 

Most researchers think airborne transmission is a major factor in the spread of this common disease. But Milton notes that updating international infection-control guidelines requires evidence from randomized clinical trials such as this one. 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. 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,” said Milton. 

The team used a quarantined floor of a Baltimore-area hotel to measure airborne transmission between five people with confirmed influenza virus with symptoms and a group of 11 healthy volunteers across two cohorts in 2023 and 2024. A similar quarantine set-up was used in an earlier study and exhaled breath testing was used in several pioneering studies by Milton and colleagues on influenza transmission. 

During the most recent flu study, participants lived for two weeks on an isolated floor of the hotel, and did daily activities simulating 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 measured a wide range of parameters throughout the experiment, 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 the ambient air of the activity room. Participant 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. 

Finding ways to control flu outbreaks is a public health priority, says Milton. Flu is responsible for a considerable burden of disease in the United States and globally – up to 1 billion people across the planet catch seasonal influenza every year and this season has seen at least 7.5 million flu cases so far in the United States alone, including 81,000 hospitalizations and over 3,000 deaths. 

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 – contributed to this study, as well as colleagues from UMD 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, Ann Arbor. 

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To set up an interview with Drs. Donald Milton or Jianyu Lai, please email sph-comm@umd.edu. 

This study was supported by NIAID Cooperative agreement U19 grant (5U19AI162130), by the University of Maryland Baltimore, Institute for Clinical & Translational Research (ICTR) and the University of Maryland Strategic Partnership: MPowering the State (MPower), and by gifts from The Flu Lab and Balvi Filantropic Fund. 

To find out more about Milton and his team’s work, watch this 2018 Matter of Fact episode. 

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Journal

PLOS Pathogens

DOI

10.1371/journal.ppat.1013153 

Method of Research

Randomized controlled/clinical trial

Subject of Research

People

Article Title

Evaluating modes of influenza transmission (EMIT-2): Insights from lack of transmission in a controlled transmission trial with naturally infected donors

Article Publication Date

8-Jan-2026

 

AI approach takes optical system design from months to milliseconds

A research group at Penn State has introduced a new, high-speed design process for nanoscopic materials used in advanced optical systems

Penn State

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A group of researchers at Penn State developed an approach that integrates artificial intelligence into metasurface design. Their work was featured on the cover of the October issue of Nanophotonics. 

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Credit: Provided by Huanshu Zhang

UNIVERSITY PARK, Pa. — A team of researchers at Penn State have devised a new, streamlined approach to design metasurfaces, a class of engineered materials that can manipulate light and other forms of electromagnetic radiation with just their structures. This rapid optimization process could help manufacture advanced optical systems like camera lenses, virtual reality headsets, holographic imagers and more, the team said.

The method, which was featured on the cover of the October issue of Nanophotonics, uses large language models (LLMs) to accurately predict how a metasurface will influence light. LLMs are a type of artificial intelligence (AI) model capable of learning and improving an action over time based on provided training data and repeated behavior. This approach bypasses the traditional metasurface simulation process that required extensive domain knowledge and time, making it possible for engineers to quickly design these nanoscopic materials and predict how they will influence light solely through prompts fed to AI.

According to Doug Werner, John L. and Genevieve H. McCain Chair Professor of electrical engineering and corresponding author on the work, metasurfaces offer much more flexibility and capability than traditional materials in nanophotonic devices — systems that can manipulate light at a scale even smaller than a wavelength of visible light.

“You can only go so far using naturally occurring materials when trying to manipulate light or other types of electromagnetic waves,” Werner explained. “Through the structure of the sub-wavelength unit cells that make up the materials, metasurfaces can manipulate the way light behaves at a nanoscopic level, allowing us to slim down optical systems that are traditionally very bulky.”

Despite their usefulness, metasurfaces are challenging to develop, according to Haunshu Zhang, a third-year electrical engineering doctoral student and first author on the paper. Zhang said that although AI has been integrated into the development process for a few years in the form of deep-learning neural networks, which mimic the non-linear way human brains can make connections, researchers would still have to go through the time-consuming and knowledge-intensive process of simulating potential designs and constructing a custom neural network for each metasurface.

This problem inspired him to integrate LLMs into the process.

“The main limitation of current neural-network-based methods is that you must try many neural network configurations in order to find one that accurately predicts how a metasurface will interact with light,” Zhang said. “By training LLMs, we can accurately predict how a metasurface will interact with light in seconds compared to the hours, days or even months it previously took, without needing specialized AI expertise or countless trials.”

The team compared their LLM-generated predictions to computer-simulated metasurfaces to test their method. The LLMs would predict how light would react when exposed to a metasurface with designated “control points” that morphed the design into a desired shape. The team then trained and compared these predictions to a data set of over 45,000 randomly generated metasurface designs. The team found that their approach provided highly accurate predictions of how light would react with the metasurfaces, while effectively eliminating the time-consuming neural network design process.

The increased efficiency allows researchers to focus on developing what Lei Kang, associate research professor of electrical engineering and co-author of the paper, called “arbitrarily shaped” metasurface elements. Lei explained how, compared to standardized shapes like cylinders or cubes, using highly specialized shapes in metasurface design can significantly impact performance and efficiency — but these free-form designs come with a substantial drawback.

“Arbitrary designs allow researchers to create application-specific metasurfaces that vastly outperform designs based on traditional shapes,” Lei said. “However, these designs couldn’t be optimized and tested effectively because traditional simulation methods would take an impractically long time to complete. By integrating LLM predictions, we can see how the metasurfaces will influence light at unprecedented speeds.”

The new method also makes engineering metasurfaces extremely approachable, according to Sawyer Campbell, associate professor of electrical engineering and co-author on the paper. The LLMs are very good at “inverse design,” or starting with the desired outcome and working backward to find the exact system, material, structure or combination of factors that produces it, he said. While inverse design of metasurfaces was possible before, the simulation process meant it could sometimes take multiple weeks or months to complete, according to Campbell.

Looking ahead, the team plans to continue developing and optimizing this new approach. According to Werner, the primary goal is to significantly reduce the design time and complexity for metasurface-enabled devices, accelerating their development and integration into commercial nanophotonic applications across the healthcare, defense, energy and consumer electronics industries. 

“We believe this approach could usher in a new standard for how industry engineers and researchers approach developing nanophotonic devices,” Werner said. “With this new method, researchers unfamiliar with the complex metasurface design process can approach the LLMs with an explanation of what they need and effectively generate it.” 

This research was supported by the John L. and Genevieve H. McCain Endowed Chair Professorship at Penn State. 

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Journal

Nanophotonics

DOI

10.1515/nanoph-2025-0343 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Chat to chip: large language model based design of arbitrarily shaped metasurfaces

Article Publication Date

7-Jan-2026

 

Marine geoscientists link warming with ancient ocean ‘salty blob’

Rutgers scientists uncover evidence that deep-sea salinity helped lock away carbon dioxide levels during the last ice age

Rutgers University

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Elisabeth Sikes (left), with Dale Hubbard of Oregon State University, alongside the large coring block used to collect deep-ocean sediment samples during the research cruise.

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Credit: Rutgers University

Climate change has many culprits, from agriculture to transportation to energy production. Now, add another: the deep ocean salty blob.

In a groundbreaking study of ancient ocean geochemistry, a Rutgers researcher and a former Rutgers graduate student have found evidence that the end of the latest ice age some 18,000 years ago, a period of rapid planetary warming, coincided with the emergence of salty water that had been trapped in the deep ocean.

The findings, published in the journal Nature Geoscience, shed new light on how salt levels in the Earth’s deepest waters may influence the amount of carbon dioxide – a principal heat-trapping gas – in the atmosphere. 

“In today’s oceans there are different major water masses, and each has a distinctive salinity,” said Elisabeth Sikes, a professor in the Department of Marine and Coastal Studies at Rutgers-New Brunswick. “Researchers have long speculated that deep ocean salinity levels were linked to changes in atmospheric carbon dioxide across ice age cycles. Our paper proves it.” 

Oceans contain vast amounts of carbon dioxide, which absorbs infrared energy and contributes to global warming. Much of this carbon is taken up by marine organisms at the surface during photosynthesis. As these organisms live, die and sink, their remains break down and release the carbon dioxide into the deep waters. The differences in salinity of the deep layers of the ocean help form a barrier between the layers, keeping the gas from returning to the atmosphere.

Warming and cooling are cyclical, and this speeds up and slows down ocean overturning circulation – known as “the global ocean conveyor belt.” During warm periods, like today, the ocean circulates faster, keeping deep water from gathering as much carbon dioxide. When ocean circulation slows and denser water sinks in cool regions, more carbon dioxide is trapped with it. Eventually, the accumulation of carbon dioxide in the deep ocean helps cool the planet, and the cycle repeats.

During the latest ice age, which peaked about 20,000 years ago, the deep ocean stored carbon dioxide more efficiently than today, Sikes said, which helps explain why average temperatures were much lower.

Scientists know that the planet’s warming at the end of the last ice age was marked by a huge release of the carbon dioxide from the deep ocean. But what happened to the salt that supposedly helped lock carbon dioxide away has remained a mystery.

“The exact mechanism, the actual physical explanation for why that happens, is something researchers have been trying to resolve,” said Ryan H. Glaubke, a postdoctoral research associate at the University of Arizona and lead author of the study. Research for the study was conducted while Glaubke was a graduate student in Sikes’ lab at the Rutgers School of Environmental and Biological Sciences.

“This paper supports the idea that it’s the salinity of deep ocean water – the ‘salty blob’ – that keeps carbon dioxide locked away for long periods of time,” Glaubke said. 

To reach this conclusion, Glaubke and Sikes analyzed the geochemical composition of sand grain-sized microfossils – formed by single-celled creatures called foraminifera – in marine sediments that they collected from the boundary of the Indian and Southern oceans, off the coast of western Australia. 

The microfossils preserve information about the water in which they formed, including its salinity, Sikes said. 

The researchers used these microfossil data to reconstruct a record of local salinity levels and found that at the onset of the last deglaciation, the shallow waters of the upper Indian Ocean suddenly became much saltier for several thousand years. This increase corresponded with other geochemical “fingerprints” that confirm the salt originated from the deep ocean.

The findings, the researchers said, are evidence of the crucial role the Southern Ocean plays in planetary climate. This is because it is one of the few places that truly deep waters – with their high load of carbon dioxide – surface and “exhale” the gas back into the atmosphere.

As researchers continue to study the current period of warming, they cannot neglect what happens in the Southern Hemisphere, Sikes said. While the ocean has absorbed about a third of all carbon emissions from human activity, without the deep ocean’s "salty blob," carbon dioxide is stored less efficiently.

“In a way, the ocean has been our greatest champion in the fight against climate change,” Glaubke said. “But without a pronounced ‘salty blob’ like the ancient glacial ocean had, it can’t hold on to our carbon emissions forever.”

An Amsterdam albatross, among the world’s rarest seabirds, seen during a Southern Ocean research expedition.

Ryan Glaubke measures and marks a sediment core used to reconstruct past deep-ocean salinity and carbon storage.

Credit

Rutgers University

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Journal

Nature Geoscience

DOI

10.1038/s41561-025-01756-7