Study: Deliberate attempt to spread influenza ends with a "surprise"

Study finds deliberate attempts to spread influenza failed, revealing limits of transmission and the role of immunity, airflow, and viral load.

A recent study conducted by researchers at the University of Maryland in the United States concluded with unexpected results about how the influenza virus is transmitted, after deliberate attempts to spread the infection among a group of volunteers in an environment conducive to the spread of the virus failed.

The experiment, designed to simulate real-life conditions, placed a group of healthy individuals in cramped hotel rooms with people who were naturally infected with the flu. Despite engaging in shared activities such as dancing, yoga, and exchanging equipment for several days, not a single case of infection was recorded among the healthy volunteers.

Conditions conducive to infection

Through this study, the researchers sought to answer a fundamental question about the most effective routes of virus transmission, whether through aerosols (microscopic droplets) or through contaminated surfaces.

To achieve this, the team created a low-ventilation environment in the hotel rooms, setting the temperature between 22 and 25 degrees Celsius and the humidity between 20 percent and 45 percent, levels that are scientifically believed to promote the virus's survival and activity.Why didn't the infection spread?

Despite tests confirming the presence of an active infection in the "donors," researchers suggest three factors that may explain the failure of virus transmission in this case:

• Low infection rate: The donors (aged 20-22) released limited amounts of the virus, with few bouts of coughing and sneezing , reducing the density of contaminated aerosols.
• Acquired immunity: The report indicated that the “recipients” (aged 25-45) had partial immunity as a result of exposure to previous flu seasons or receiving previous vaccines, which raised their threshold for infection.
• Air dynamics: Researchers believe that using fans inside rooms, despite poor external ventilation, helped disperse the virus clouds and prevent them from concentrating around healthy volunteers.

The study results indicate that simply being in an enclosed space with an infected person may not be enough to transmit the infection in the absence of "super-spreaders" or severe symptoms such as a persistent cough.

However, the researchers stressed that these findings do not diminish the seriousness of influenza, which affects millions annually, but rather highlight that its transmission is subject to a complex system that includes the immune status of the recipient and the strength of viral emission from the infected person.