We all hope to avoid illness when someone close by gets sick. Our bodies, however, aren’t taking any chances.

If the skies threaten rain, we grab an umbrella. Our body’s immune system might do the equivalent when someone around us catches a bug.

A Chapman University biological sciences researcher in Orange, California, says our immune systems kick into gear after we see a sick person. This occurs even when we’re not ill.Our brains might be sending an alert to the immune system that there is trouble in the neighborhood, so prepare.

The researcher’s study reviewed scientific work on the phenomenon in humans and other species. Her conclusion: Pathogens need not infect us to trigger the body’s defenses.

She points to a study in which healthy people were shown pictures of others sneezing and coughing. Blood tests showed those who viewed the images had higher levels of an immune-boosting molecule in their blood even though they were not sick themselves.

Scientists see something similar with other species, too. For example, female Japanese quail mating with immunocompromised males produce eggs with elevated levels of a disease-fighting agent. Investigators say this phenomenon is an example of how we are all interconnected. Our health is a communal affair. And this needs to be understood for better insight into how disease spreads.

More laboratory work is needed to see how effectively this preemptory immune response is in stopping or slowing disease.

You still might want to keep your distance from that sneezing, wheezing co-worker. An umbrella, after all, is useless in a hurricane.