Lead researcher Mark Schaller said that he was taking a bit of a flier by looking for such an effect, but it wasn't totally crazy. Earlier studies had shown that pictures of sick people can cause stress and that certain kinds of stress can influence the immune system.
Schaller and his colleagues used 28 volunteers. All of them first saw a neutral set of slides showing furniture before the initial immune responses were measured. Half then saw a set of slides meant to be stressful - pictures of people aiming guns at them.
The other half got the sniffling, sneezing and pox.
The researchers measured the immune response again after these slides. The result: The interleukin-6 shot up significantly more in those exposed to the sick people than those seeing the gun photos.
Perhaps we evolved this ability to protect us from catching infections. But Schaller said there was also a potential downside since turning up the immune system is associated with inflammation and long-term damage.
Would doctors and nurses suffer from chronic immune overdrive, then? Schaller said researchers had not studied the possibility yet, but it is possible that health-care workers adjust. "People do habituate to think quickly," he said.