A study has found that even just seeing a person who is coughing, who may be potentially contagious, activates our body's immune system. This means that the body reacts first out of concern that pathogens from an infected person may be transmitted.
Researchers from the University of Geneva in Switzerland revealed that immune responses can be triggered by visual stimuli alone using virtual reality (VR) technology. The findings were published in the international journal 'Nature Neuroscience' on the 28th.
The research team conducted five experiments with 248 healthy participants wearing VR headsets. Initially, they were shown an avatar with a neutral expression approaching them, and then the participants were divided into several groups and shown the same avatar again. At this point, some participants were shown avatars that displayed typical symptoms of infectious diseases, such as skin rashes, or appeared frightened.
The experiment showed that when the avatar appeared to be sick, participants exhibited movements indicating they wanted to distance themselves. Additionally, analyses of participants' brain waves, functional magnetic resonance imaging (fMRI), and blood samples revealed that the immune cells of those who saw the infected-looking avatar were actually activated. When certain areas of the brain are activated, blood flows toward those areas, and fMRI shows these regions as if they are lit up.
In particular, immune cells known as 'innate lymphocytes' were activated. These cells respond first when threats arise from outside and alert other immune cells. Warning signals were triggered simply by viewing images that appeared to be infected, rather than actual pathogens.
Camilla Jandus, a professor at the University of Geneva who led the study, said, "It seems that just seeing a potentially infectious person prompts our body to go into a state of preparedness."
Esther Diekhof, a researcher from the University of Hamburg in Germany who did not participate in this study, also noted, "This once again confirms the mechanism by which the immune system shifts to a state of readiness before pathogens enter the body."
However, it is still unclear whether this reaction actually helps prevent or overcome actual infections. Benedict Seddon, a professor at University College London in the UK, stated, "When infected with the coronavirus that causes severe acute respiratory syndrome (SARS-CoV), it may take 1 to 2 days for the immune system to recognize and respond to it," and added, "More research is needed to determine whether the response to visual information leads to infection prevention."
References
Nature Neuroscience (2025), DOI: https://doi.org/10.1038/s41593-025-02008-y