The Mere Sight of Someone Sick Triggers an Immune Response, Study Suggests

Researchers equipped study participants with virtual reality headsets and observed how their brains and immune systems reacted to avatars with signs of illness

Sara Hashemi | Daily Correspondent

July 31, 2025

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When you see someone coughing on a train platform, your reaction might be to keep a safe distance. But there might be more going on inside your body: Now, scientists have found that the sight of a person looking potentially infectious is enough to trigger an immune response in humans.

The work is described in a new paper published Monday in the journal Nature Neuroscience.

In a series of experiments, researchers had 248 participants wear virtual reality goggles and watch human avatars approach them. Sometimes, the avatars appeared neutral or fearful, and in other cases, they showed signs of illness, like coughing or rashes.

Participants responded differently to the sick-looking avatars. In one of the experiments, participants were asked to press a button when they felt a mild touch to the face. They reacted faster when viewing a sick-looking avatar, suggesting the sight made them more aware of the space around their body.

Brain imaging revealed that different regions of the brain were activated when the participants saw the infectious avatars. They fired up the areas related to personal space, as well as in the brain’s salience network—the regions that detect threats. The hypothalamus, which communicates with other parts of the body, such as the immune system, also became active. Neural activity was initiated from farther away when viewing a sick face compared to the neutral and fearful avatars.

The team also found that these reactions related to an activation of immune cells in the blood. These cells—known as innate lymphoid cells—are like the body’s first responders, as they alert other immune cells to threats.

This shows that “the immune system is intimately tied to the [central nervous system], and the recognition of threat is immediately translated to the immune system to produce a preparatory response,” says Michael Irwin, a psychiatrist and biobehavioral scientist at the University of California, Los Angeles, who was not involved in the research but peer-reviewed the study, to Claudia López Lloreda at the Transmitter.

The study is “unique in demonstrating that people’s immune system can be primed just by the visual recognition that someone looks sick,” Irwin adds to Simon Makin at Science News. “That’s really remarkable.”

Other study participants received a dose of a flu vaccine, so the team could measure their response to actual contact with a pathogen. Their activation of innate lymphoid cells paralleled what researchers had measured in the participants exposed to the sick faces in virtual reality.

“For a long time, we’ve sort of had the hunch that our brains respond to potential infective threats, but I think this study really does a very nice job in beginning to show how mechanistically that is enacted in the brain,” says Neil Harrison, an immunopsychiatry researcher at Cardiff University in Wales who was not involved in the work, to the Transmitter.

Still, questions remain. The brain imaging tests were only done on a small subset of the group, and further research will have to replicate the results, reports the Transmitter. The study also focused primarily on young adults, so future work should include older participants as well.

Benedict Seddon, who researches the immune system at University College London and was not involved in the study, tells Nicola Davis at the Guardian that the research doesn’t confirm whether the triggered immune response actually helps the body fight an infection. “When we get infected, by Sars-CoV for instance, it can take a day or two for the infection to establish and for the immune system to become aware of it and respond, a long time after the initial encounter that stimulated this short-lived mobilization,” he explains.

More work in this field can help scientists apply their findings to potential treatments. For instance, the study authors are hopeful that virtual reality could be used to improve vaccine administration by increasing the activation of immune cells, reports Katie Kavanagh at Nature. Or, it could be used to raise the efficacy of painkillers.

“If you have flu and take paracetamol, for instance, you could use virtual reality to boost the effect by modulating the immune system reaction,” Andrea Serino, a neuroscientist at the University of Lausanne in Switzerland and one of the study authors, says to Science News.

For now, the team is working on expanding the study and replicating the results. But maybe in time, we’ll be wearing virtual reality headsets to flu shot appointments.

Sara Hashemi | Read More

Sara Hashemi is a science writer and fact-checker currently based in New York City. Her work has appeared in Sierra, The Body, Maisonneuve magazine and more.