No Flu Transmission in Controlled Experiment Highlights Ventilation and Behavioral Factors

A controlled experiment revealed that influenza transmission can be prevented indoors through proper ventilation and behavioral factors—even among close contacts.

The study, conducted between 2023 and 2024, placed five influenza-infected college students with 11 healthy middle-aged volunteers in a hotel room for two weeks. Despite close proximity and daily social interactions, no infections occurred among the participants.

Researchers attributed the lack of transmission to a combination of factors. A ventilation system consisting of a heater and dehumidifier rapidly mixed air, diluting viral particles in the environment.

Infected participants rarely coughed, a behavior identified as a major contributor to airborne spread. Dr. Jianyu Lai noted, 'Our data suggests key things that increase the likelihood of flu transmission—coughing is a major one.'

The study also highlighted age-related differences in susceptibility. Middle-aged adults showed lower infection rates compared to younger participants, though the exact mechanisms remain unclear.

Dr. Donald Milton emphasized the role of environmental conditions, stating, 'Being up close, face-to-face with other people indoors where the air isn't moving much seems to be the most risky thing.'

Viral exposure was monitored through nasal swabs, saliva samples, and air measurements. The Gesundheit II machine, a device designed to capture exhaled breath aerosols, was used to quantify airborne viral load.

The researchers caution that the findings are based on a small sample and require validation in larger populations.