Hotel-apartments full of fluey students and no healthy volunteers fell ill – bold experiment a potential game-changer in understanding flu spread

A university in the U.S. has conducted a bold real-world experiment. Placing flu patients alongside healthy volunteers, the two groups spent several days indoors alongside each other. The results have surprised veteran and younger researchers alike, and many of those participating. Where the flu was expected to widely spread, precisely the opposite happened, the virus was not caught by any of the healthy volunteers. Researchers have closely examined the risk-mitigating measures they implemented in the experiment, to definitively land on the effectiveness of each and why they were so effective.

Key findings

Limiting coughing and well-circulated indoor air were found to be key in reducing virus levels, even with the close proximity of all involved. The medical-scientists also found that age may have been an assisting factor too, with middle-aged humans having a lower likelihood of catching the flu than younger people.

For health and aged care services across the world, the researchers are encouraged by the findings and indicate they are able to recommend that the results could mean policy and program implementations in multiple sectors. The results showcase that air movement, maintained ventilation and masks are robust defenses against infection.

Flu season seriousness

Particularly in the wake of COVID, researchers have been seeking breakthroughs in not just the treatment of influenza strains but the slow-down and goal of complete mitigation of its spread.

Post the outbreak of COVID, new strains of influenza continue to emerge, with the world experiencing an especially virulent variant dubbed “subclade K”. The need to provide insight into how people can better protect themselves from getting sick continues to be vital.

With the numbers continuing to be in the staggering levels, researchers are emphatic that mitigation strategies need further progress to help relieve infection rates and unsustainable burdens on health networks the world over. Across the U.S. 2024-2025 winter flu season, the numbers alone paint a stark picture. 7.5 million cases have been identified, with 81,000 hospitalisations and over 3000 deaths.

Unorthodox  

The researchers, comprised of a team of researchers from the University of Maryland Schools of Public Health and Engineering in College Park and the School of Medicine in Baltimore, designed an unorthodox experiment. They wanted to better gauge how flu strains have been able to move so freely between people.

College students who initially tested positive for the flu, were then placed inside hotel rooms with healthy middle-aged volunteer carers. Surprisingly, despite the close proximity, not one of the healthy participants became infected.

Dr. Donald Milton, a world-renowned infectious disease aerobiology expert and professor at SPH’s Department of Global, Environmental and Occupational Health questioned, “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?” With it’s bold construction, the study was set up to directly answer his question.

In keeping with his previous record, being one of the first experts to discern ways to stop the spread of COVID, Dr. Milton continues to seek to bring that learning to other strains of influenza that continue to impact millions.

Clinical trial

While unorthodox the study was conducted as a controlled clinical trial. Published last week in PLOS Pathogens, it is seen as the first of its kind to closely assess airborne flu transmission between persons who were ordinarily infected, as opposed to artificially infected in a laboratory, and those who were healthy.

Milton and colleague Dr Lai set about investigating why none of the middle-aged adults in the study contracted the flu.

Lai, a post-doctoral research scientist shares, “our data suggests key things that increase the likelihood of flu transmission — coughing is a major one.”

He assessed that upon viewing the footage of the study, while the infected students had high levels of the virus situated in their noses, the behavioural expression of the illness did not manifest in coughing. Subsequently, Lai believes, only minimal pathogens of the virus came into the shared air in the hotel rooms.

Ventilation and age

Ventilation was also seen to be a pivotal approach to mitigating spread. Lai notes, “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.”

And lastly, a factor that provider leadership may do well to note and implement in hiring decisions, age may have been another protective measure. For middle aged and more senior applicants to aged care facilities and home-care work, it looks to be that the science now supports these staff members as having an edge to remain healthier in the face of infected residents and clients.

Lai highlights that middle-aged adults, bolstered by other peer-reviewed trials, have a reduced tendency to be susceptible to influenza than people younger in years. He believes age to be a strong factor which contributed to the low-spread in their study.

Valuable clues for further study

Airborne transmission continues to be the vehicle of spreading that most scientists agree on. Milton assesses that in order to further the understanding of spread and mitigation, strong evidence, from randomised studies like theirs, is needed. The team continues to work towards the creation and conduct of more studies to provide deeper insight.

The positive results in the recent study may yet prove invaluable in providing clues as to how people around the world can minimise their flu risk each season.

“Being up close, face-to-face with other people indoors where the air isn’t moving much seems to be the most risky thing”, Milton assesses, “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.”