Scientists Put Flu Patients in a Room With Healthy People—No One Got Sick. Why?

• In a new study, researchers mixed five people with flu infections with 11 people who did not have the virus in a hotel room with limited ventilation but high air circulation.

• Ultimately, none of the healthy participants became ill; this may be due to the participants’ age (and natural immunity to flu), among other factors.

• Doctors say this suggests that providing air circulation and wearing an N95 mask may help prevent the spread of the flu.

a common part recommendation Open reduce your risk of flu Avoiding being around people who are clearly sick. However, scientists have recently done the opposite and I have the flu in the same room as healthy participants as part of a small new study. (All participants provided written informed consent before enrolling in the study and reserved the right to withdraw at any time.)

Surprisingly, no one was infected.

“Our goal in this study was not to prevent flu,” says infectious disease aerobiologist Donald Milton, M.D.Co-author and professor in the Department of Global, Environmental and Occupational Health at the University of Maryland School of Public Health. “We were trying to understand how transmission occurs so we can design better ways to prevent it from happening.”

Milton states: eight percent People catch the flu during a normal respiratory virus season, making it a highly contagious virus.

So why didn’t healthy people catch the flu even if they were in the same room with infected people? The findings offer some important implications for flu prevention, whether someone in your household has the virus or you just want to hedge the risk.

Meet the experts: Amesh A. Adalja, MDHe is an infectious diseases expert and senior fellow at the Johns Hopkins Center for Health Security. Thomas Russo, M.D. He is a professor and chief of infectious diseases at the University at Buffalo in New York. Infectious diseases aerobiologist Donald Milton, M.D.is a co-author of the study and a professor in the Department of Global, Environmental and Occupational Health at the University of Maryland School of Public Health.

What did the research find?

for PLOS Pathogens In the study, researchers mixed five people infected with the flu with 11 people who did not have the virus in a hotel room with limited ventilation but high air circulation.

Study participants lived on an isolated hotel floor for two weeks and engaged in daily routines designed to mimic real-life social interactions, such as casual conversations, yoga, stretching and dancing. Infected people touched things like pens, tablets and microphones, which were then distributed to the group.

During this time, researchers tracked participants’ symptoms and collected daily data such as nasal swabs, saliva and blood samples. They also measured virus levels in the participants’ air and breath.

As a result, none of the healthy participants became ill.

Why wasn’t everyone infected?

There are probably several reasons for this. Dr. “Most people will find it shocking to realize that when scientists tried to put people in a room to see if infected people could transmit flu to uninfected people, it didn’t work,” says Milton. “This is so weird.”

His team speculated that this was because previous studies used laboratory viruses that had been circulating years ago (and to which people had developed immunity); Therefore, they decided to use people naturally infected with existing strains of the virus.

However, Dr. Milton thinks one reason the healthy participants didn’t get sick was because they were middle-aged adults who had been exposed to the flu for years. As a result, he says, they may have more natural immunity than young people.

The study was also conducted in a milder flu year (2023-2024). this yearDr. Milton notes: Most study participants had high levels of flu virus in their noses but were not coughing. “In previous years, we found that people who did not cough did not spread much virus,” he says. “Cases of flu that people cough up are the most contagious.”

Dr. Milton said the ventilation was “pretty bad on purpose” as investigators closed the doors and did their best to limit ventilation. But the air was also moving around the room a lot. “We wanted to have a well-mixed environment, considering that everyone would be exposed,” he says. “Apparently, the opposite worked as well. There was enough air in the room, and with people not coughing as much, everyone was exposed to a very small amount of the virus, which wasn’t enough.”

What is the takeaway from staying well?

Doctors say there are a few things you can do with this information, whether you’re out or someone in your home is sick. Limiting coughing (using cough suppressants or having the sick person wear a mask around others) may be helpful. Amesh A. Adalja, MDInfectious diseases expert and senior fellow at the Johns Hopkins Center for Health Security.

“Cough is an important mechanism by which viral particles spread into the air,” he explains. “Reducing cough reduces the opportunity for respiratory viruses to spread.”

Good airflow is also helpful, he says Thomas Russo, M.D. He is a professor and chief of infectious diseases at the University at Buffalo in New York. “It is often difficult to open windows during the winter months because it is cold and indoor air circulation is quite poor,” he says. “But using an air filter at home is a sensible idea.” Dr. Turning on ceiling fans can also help, says Milton. Dr. Adalja agrees. “The better the airflow, the less likely it is that airborne viral particles will hit another individual,” he says.

However, Dr. Milton says one of the best ways to protect yourself is to wear an N95 mask; especially if you are around people who are coughing. “Ultimately, all these layers of protection are working, and this shows,” he says.

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